[xk] Alternator Conversion

XK
1

Since my generator died, I decided to convert to negative ground and an
alternator. I’ll save the generator for future generations. In the meantime,
has anyone found an alternator which installs easily, without making a new
bracket?

I have found an early 70s American Motors alternator (52 amp) which has the
correct offset from the back of the front pivot bracket. The only problem is
that it doesn’t have a built-in regulator, which would simplify things
tremendously since neither the alternator nor the regulator come with
instructions or a wiring diagram.

Thanks in advance,

“Mark 1” Mark Stephenson
1952 XK120 Roadster #673129 (w/XK140 engine and C head)
1958 3.4 Litre Saloon / 1984 XJ6 4.2L / 1985 XJ6 VDP
Jaguar Club of Central Arizona (USA) – www.cableone.net/jcca

2

Here is the latest on the alternator conversion:

My local AutoZone was kind enough to let me peruse their alternator
inventory in search of one with a similar configuration to the Lucas
generator. After going through about 20, I found a 52 (or 55, depending on
where you look) amp Motorola alternator with the exact same pulley
placement. In case anyone is interested it is AutoZone part number 7429. It
will bolt on the front of the generator bracket just like the generator,
with a 3/8x8" bolt through the alternator, the bracket and steel tube (for
rigidity) and out the back. The alternator was a mere $39.99 + $15.00 core.
The only drawback is that it doesn’t have a built in regulator, so I had to
track one of those down. Again AutoZone was very helpful, helping me search
the pages, looking for the number amidst all the generator numbers listed. I
told them to take care of other customers and I’d continue the search and
much to my surprise, and theirs, I discovered a listing of applications by
alternator number at the back of their book. That’s how I discovered, much
to my chagrin, that it was early 70s American Motors. They had a regulator,
but I wasn’t sure how it was going to work, so I held off on that.

Then I went to the library, in disguise because I didn’t want anyone to
recognize me as I checked out books for early 70s Gremlins, Hornets, and
Matadors. (How embarrassing!) After learning how the regulator fit into the
scheme of things, I returned to AutoZone for the VR727 regulator, US$16.99.

Both have lifetime warranties.

After examining Gremlin and XK120 (I hate to use those two words together in
the same sentence.) wiring diagrams in detail, and while it’s still fresh in
my mind (before I head off to bed), I’m hoping some of the electrical
geniuses on the list can verify my theories regarding alternators vs.
generators.

With a generator and a regulator, the regulator controls the output of the
generator directly by adjusting the voltage and amperage before it flows to
the battery. As I see it, the raw generator output doesn’t change (unless
the field strength is adjusted to control output). The regulator for an
alternator, on the other hand, controls the alternator so it only puts out
the amperage needed to power the electrical system and charge the battery.

Am I correct so far?

If so, I’ll continue on my mad dash to electrical nirvana…

I want to keep as many of the original components with the car in case a
miracle happens and the original engine turns up. I have the RF95 Control
Box, which includes a terminal block and some fuses. I’ve figured out what
goes where and why, and rather than reinvent the wheel, I might as well use
the terminal block feature of the control box. It seems to me that I’d have
to disable the regulator part of the box, though, since I’ll be powering
directly to the battery from the alternator.

Am I still on the right track?

It seems that to adapt the RF95, all I would need to do is disconnect the
ground wire from terminal E; remove the field wire from terminal F, since
I’m going to use that wire for the new regulator; and move the generator
(now alternator) output wire from terminal D to terminal A. At that point I
would have a really impressive looking terminal block, right?

Finally, I want to keep extraneous wires to a minimum. I have the 10 ga.
yellow wire that ran from the generator output to the D terminal on the
RF95, that will now run from the alternator to terminal A. I don’t want to
fry that wire, and I know the 75 amp Lucas alternators use two 10 ga. wires
from the alternator, so I was considering a second 10 ga. wire that would
run from the alternator output to the big battery wire post on the solenoid.
Anyone see any problems with that?

Then I just have to connect the American Motors regulator wires to the
proper terminals on the back of the alternator and I should be in business,
correct?

Assuming that I have figured out everything so far, the only thing I’m not
sure about is how the alternator ties into the ammeter. Even if someone has
converted to an alternator with a built-in regulator, I think your
connection method will still apply, because there aren’t that many options.

As far as the ignition light goes, I have a little better idea, I think.
There’s a wire that runs from what is called the “regulator terminal” on the
alternator to the regulator, and on the Gremlin, it also seems to run to the
ignition light, then to ground. However, I wasn’t sure about the schematic
because the ignition light was not specifically identified. It was the only
component, lumped into the dash circuitry, that had a line running from the
regulator. Does that make sense?

I know I’ve asked a lot of questions, but I hope that the listing of the
alternator and regulator part numbers will be some miniscule repayment for
the information I have and will continue to receive from the great minds of
the list.

“Mark 1” Mark Stephenson
1952 XK120 Roadster #673129 (w/XK140 engine and C head)
1958 3.4 Litre Saloon / 1984 XJ6 4.2L / 1985 XJ6 VDP
Jaguar Club of Central Arizona (USA) – Internet Service Provider, TV & Phone | Sparklight Original Message -----
From: “Mark Stephenson” <@Mark_Stephenson4>
To: “XK Lovers” xk@jag-lovers.org
Sent: Sunday, December 12, 1999 9:46 PM
Subject: [xk] Alternator Conversion

Since my generator died, I decided to convert to negative ground and an
alternator. I’ll save the generator for future generations. In the
meantime,
has anyone found an alternator which installs easily, without making a new
bracket?

I have found an early 70s American Motors alternator (52 amp) which has
the
correct offset from the back of the front pivot bracket. The only problem
is
that it doesn’t have a built-in regulator, which would simplify things
tremendously since neither the alternator nor the regulator come with
instructions or a wiring diagram.

Thanks in advance,

“Mark 1” Mark Stephenson
1952 XK120 Roadster #673129 (w/XK140 engine and C head)
1958 3.4 Litre Saloon / 1984 XJ6 4.2L / 1985 XJ6 VDP
Jaguar Club of Central Arizona (USA) – Internet Service Provider, TV & Phone | Sparklight

3

Mark

the only thing I can comment on is that you can use the ammeter but it will
have to be converted to 60+ / -60 reading this is to take account of the
extra umph from the alternator. see Jaguar World January Issue.

keep up the good work

looking at your e-mail address, are you from the astronomy fraternity?

Peter M> -----Original Message-----

From: Mark Stephenson [SMTP:marks@starlink.com]
Sent: 16 December 1999 10:26
To: xk@jag-lovers.org
Subject: Re: [xk] Alternator Conversion

Here is the latest on the alternator conversion:

My local AutoZone was kind enough to let me peruse their alternator
inventory in search of one with a similar configuration to the Lucas
generator. After going through about 20, I found a 52 (or 55, depending on
where you look) amp Motorola alternator with the exact same pulley
placement. In case anyone is interested it is AutoZone part number 7429.
It
will bolt on the front of the generator bracket just like the generator,
with a 3/8x8" bolt through the alternator, the bracket and steel tube
(for
rigidity) and out the back. The alternator was a mere $39.99 + $15.00
core.
The only drawback is that it doesn’t have a built in regulator, so I had
to
track one of those down. Again AutoZone was very helpful, helping me
search
the pages, looking for the number amidst all the generator numbers listed.
I
told them to take care of other customers and I’d continue the search and
much to my surprise, and theirs, I discovered a listing of applications by
alternator number at the back of their book. That’s how I discovered, much
to my chagrin, that it was early 70s American Motors. They had a
regulator,
but I wasn’t sure how it was going to work, so I held off on that.

Then I went to the library, in disguise because I didn’t want anyone to
recognize me as I checked out books for early 70s Gremlins, Hornets, and
Matadors. (How embarrassing!) After learning how the regulator fit into
the
scheme of things, I returned to AutoZone for the VR727 regulator,
US$16.99.

Both have lifetime warranties.

After examining Gremlin and XK120 (I hate to use those two words together
in
the same sentence.) wiring diagrams in detail, and while it’s still fresh
in
my mind (before I head off to bed), I’m hoping some of the electrical
geniuses on the list can verify my theories regarding alternators vs.
generators.

With a generator and a regulator, the regulator controls the output of the
generator directly by adjusting the voltage and amperage before it flows
to
the battery. As I see it, the raw generator output doesn’t change (unless
the field strength is adjusted to control output). The regulator for an
alternator, on the other hand, controls the alternator so it only puts out
the amperage needed to power the electrical system and charge the battery.

Am I correct so far?

If so, I’ll continue on my mad dash to electrical nirvana…

I want to keep as many of the original components with the car in case a
miracle happens and the original engine turns up. I have the RF95 Control
Box, which includes a terminal block and some fuses. I’ve figured out what
goes where and why, and rather than reinvent the wheel, I might as well
use
the terminal block feature of the control box. It seems to me that I’d
have
to disable the regulator part of the box, though, since I’ll be powering
directly to the battery from the alternator.

Am I still on the right track?

It seems that to adapt the RF95, all I would need to do is disconnect the
ground wire from terminal E; remove the field wire from terminal F, since
I’m going to use that wire for the new regulator; and move the generator
(now alternator) output wire from terminal D to terminal A. At that point
I
would have a really impressive looking terminal block, right?

Finally, I want to keep extraneous wires to a minimum. I have the 10 ga.
yellow wire that ran from the generator output to the D terminal on the
RF95, that will now run from the alternator to terminal A. I don’t want to
fry that wire, and I know the 75 amp Lucas alternators use two 10 ga.
wires
from the alternator, so I was considering a second 10 ga. wire that would
run from the alternator output to the big battery wire post on the
solenoid.
Anyone see any problems with that?

Then I just have to connect the American Motors regulator wires to the
proper terminals on the back of the alternator and I should be in
business,
correct?

Assuming that I have figured out everything so far, the only thing I’m not
sure about is how the alternator ties into the ammeter. Even if someone
has
converted to an alternator with a built-in regulator, I think your
connection method will still apply, because there aren’t that many
options.

As far as the ignition light goes, I have a little better idea, I think.
There’s a wire that runs from what is called the “regulator terminal” on
the
alternator to the regulator, and on the Gremlin, it also seems to run to
the
ignition light, then to ground. However, I wasn’t sure about the schematic
because the ignition light was not specifically identified. It was the
only
component, lumped into the dash circuitry, that had a line running from
the
regulator. Does that make sense?

I know I’ve asked a lot of questions, but I hope that the listing of the
alternator and regulator part numbers will be some miniscule repayment for
the information I have and will continue to receive from the great minds
of
the list.

“Mark 1” Mark Stephenson
1952 XK120 Roadster #673129 (w/XK140 engine and C head)
1958 3.4 Litre Saloon / 1984 XJ6 4.2L / 1985 XJ6 VDP
Jaguar Club of Central Arizona (USA) – Internet Service Provider, TV & Phone | Sparklight

----- Original Message -----
From: “Mark Stephenson” marks@starlink.com
To: “XK Lovers” xk@jag-lovers.org
Sent: Sunday, December 12, 1999 9:46 PM
Subject: [xk] Alternator Conversion

Since my generator died, I decided to convert to negative ground and an
alternator. I’ll save the generator for future generations. In the
meantime,
has anyone found an alternator which installs easily, without making a
new
bracket?

I have found an early 70s American Motors alternator (52 amp) which has
the
correct offset from the back of the front pivot bracket. The only
problem
is
that it doesn’t have a built-in regulator, which would simplify things
tremendously since neither the alternator nor the regulator come with
instructions or a wiring diagram.

Thanks in advance,

“Mark 1” Mark Stephenson
1952 XK120 Roadster #673129 (w/XK140 engine and C head)
1958 3.4 Litre Saloon / 1984 XJ6 4.2L / 1985 XJ6 VDP
Jaguar Club of Central Arizona (USA) – Internet Service Provider, TV & Phone | Sparklight

4

Mark,

I think I can answer a couple of your questions.

Mark Stephenson wrote:

Finally, I want to keep extraneous wires to a minimum. I have the 10 ga.
yellow wire that ran from the generator output to the D terminal on the
RF95, that will now run from the alternator to terminal A. I don’t want to
fry that wire, and I know the 75 amp Lucas alternators use two 10 ga. wires
from the alternator, so I was considering a second 10 ga. wire that would
run from the alternator output to the big battery wire post on the solenoid.
Anyone see any problems with that?

This will work fine, except your ammeter readings will be incorrect, at
least for charge readings. See below.

Then I just have to connect the American Motors regulator wires to the
proper terminals on the back of the alternator and I should be in business,
correct?

I’m not sure how the AMC regulator is wired, but one thing to consider
is how the alternator will be ‘excited’. There is usually a terminal on
an alternator that connects to the ignition warning light (charge idiot
light). The other side of the warning lamp is conected to the plus
terminal of the battery. This provides two functions, lighting the lamp
under the right circumstances, and, more importantly, providing a small
current to the alternator field coil until the alternator starts
producing current on its own. Generators don’t need this, but all
except ‘one-wire’ alternators do. Certainly the regulator and
alternator could be designed to provide this in another way.

Assuming that I have figured out everything so far, the only thing I’m not
sure about is how the alternator ties into the ammeter. Even if someone has
converted to an alternator with a built-in regulator, I think your
connection method will still apply, because there aren’t that many options.

Basically, the alternator output should be connected to one side of the
ammeter, the battery should be connected to the other side of the
ammeter. All other electrical loads should be connected directly or
indirectly to the alternator side of the ammeter. The ammeter simply
show whether current is flowing into or out of the battery. No other
current should flow through it, although there may be occasional
instances where a small load is wired on the battery side.

As far as the ignition light goes, I have a little better idea, I think.
There’s a wire that runs from what is called the “regulator terminal” on the
alternator to the regulator, and on the Gremlin, it also seems to run to the
ignition light, then to ground. However, I wasn’t sure about the schematic
because the ignition light was not specifically identified. It was the only
component, lumped into the dash circuitry, that had a line running from the
regulator. Does that make sense?

As stated above, there is typically a circuit from the battery positive
terminal, through the warning light, through the field coil, through the
regulator to ground. The alternator output is also internally
connected to the positive side of field coil on most alternators. (But
some Lucas alternators, for example, have an additional external
terminal for this, which must be switched on and off by additional
ignition switch contacts or a relay). It could be wired a few different
ways, as long as the regulator sensing voltage comes from the alternator
output or battery, the regulator is in series with the field coil, and
somehow the field coil gets energized to kick-start the alternator.

Hope this helps.

–John

5

John,

I think I have the bases covered, but before I fry something here’s how it
ended up. (By the way, when I get this done, I’ll do a complete write up for
anyone else who would like to perform this low-cost (except for time)
conversion.±--------+
|/|| |++
|V| | || ||| Output Terminal (large nut)
| | | || | ++
[ = [ || |= Regulator Terminal (small Nut)
| | | || |_
|^| | || |_| Ground Terminal (spade)
|/|| |- Field/Brush Terminal (spade)
±--------+

The generator’s Output Terminal originally went to the D terminal on the 120
control box which ran through the regulator, contacts, a couple series
windings and came out at terminal A. I bypassed all of the control box
internals and connected the alternator Output Terminal directly to Terminal
A. Inside the control box, Terminal A is also connected, via another series
winding, to Terminal A1 which powers the headlight switch. I didn’t change
that.

The Regulator Terminal connects to the orange wire on the AMC regulator.
Because the AMC regulator is an opaque epoxy sealed unit, I can’t tell you
any more than the wire colors, but in the AMC car, that wire also connects
to one side of the ignition light. The other side of the light may go to
ground, but since they don’t break down the dashboard circuitry in the AMC
manual, it could just as easily go to battery. In the 120, the ignition
light was connected on one side to the D terminal (where the generator
output was connected) on the 120 control box; and on the other, through the
starter button to the starter solenoid (where I’m guessing it picked up
battery current when the solenoid was not actuated).

The Ground Terminal goes to a black wire on the AMC regulator.

The Field or Brush (depending on the book) Terminal hooks to a dark green
wire on the AMC regulator.

So it looks to me like the Regulator Terminal excites the field, but that
leaves me wondering what the Field/Brush Terminal does. Since it’s not
connected to anything but the regulator, I should be OK … right?.

Finally, the yellow wire on the AMC regulator goes to the coil, the starter
relay, the fuse box, and the rest of the car, so I’m thinking that’s the
“juice” for the regulator. I have that hooked into the ignition-switch
switched side of the 120 control box – Terminal A3.

As far as bypassing the ammeter with one wire and the ammeter reading being
incorrect, I don’t think 50 amps max will be carried by one 10 Ga. wire,
will it? One benefit: it might alleviate the problem of too much voltage
through the old 30 amp max ammeter.

If anyone can see any obvious errors, please let me know – I have $39.99
and/or $16.99 riding on my logic. (That’s a scary thought!)

“Mark 1” Mark Stephenson
1952 XK120 Roadster #673129 (w/XK140 engine and C head)
1958 3.4 Litre Saloon / 1984 XJ6 4.2L / 1985 XJ6 VDP
Jaguar Club of Central Arizona (USA) – Internet Service Provider, TV & Phone | Sparklight

----- Original Message -----
From: “John Loring” loring@datawatch.com
To: xk@jag-lovers.org
Sent: Thursday, December 16, 1999 1:18 PM
Subject: Re: [xk] Alternator Conversion

Mark,

I think I can answer a couple of your questions.

Mark Stephenson wrote:

Finally, I want to keep extraneous wires to a minimum. I have the 10 ga.
yellow wire that ran from the generator output to the D terminal on the
RF95, that will now run from the alternator to terminal A. I don’t want
to
fry that wire, and I know the 75 amp Lucas alternators use two 10 ga.
wires
from the alternator, so I was considering a second 10 ga. wire that
would
run from the alternator output to the big battery wire post on the
solenoid.
Anyone see any problems with that?

This will work fine, except your ammeter readings will be incorrect, at
least for charge readings. See below.

Then I just have to connect the American Motors regulator wires to the
proper terminals on the back of the alternator and I should be in
business,
correct?

I’m not sure how the AMC regulator is wired, but one thing to consider
is how the alternator will be ‘excited’. There is usually a terminal on
an alternator that connects to the ignition warning light (charge idiot
light). The other side of the warning lamp is conected to the plus
terminal of the battery. This provides two functions, lighting the lamp
under the right circumstances, and, more importantly, providing a small
current to the alternator field coil until the alternator starts
producing current on its own. Generators don’t need this, but all
except ‘one-wire’ alternators do. Certainly the regulator and
alternator could be designed to provide this in another way.

Assuming that I have figured out everything so far, the only thing I’m
not
sure about is how the alternator ties into the ammeter. Even if someone
has
converted to an alternator with a built-in regulator, I think your
connection method will still apply, because there aren’t that many
options.

Basically, the alternator output should be connected to one side of the
ammeter, the battery should be connected to the other side of the
ammeter. All other electrical loads should be connected directly or
indirectly to the alternator side of the ammeter. The ammeter simply
show whether current is flowing into or out of the battery. No other
current should flow through it, although there may be occasional
instances where a small load is wired on the battery side.

As far as the ignition light goes, I have a little better idea, I think.
There’s a wire that runs from what is called the “regulator terminal” on
the
alternator to the regulator, and on the Gremlin, it also seems to run to
the
ignition light, then to ground. However, I wasn’t sure about the
schematic
because the ignition light was not specifically identified. It was the
only
component, lumped into the dash circuitry, that had a line running from
the
regulator. Does that make sense?

As stated above, there is typically a circuit from the battery positive
terminal, through the warning light, through the field coil, through the
regulator to ground. The alternator output is also internally
connected to the positive side of field coil on most alternators. (But
some Lucas alternators, for example, have an additional external
terminal for this, which must be switched on and off by additional
ignition switch contacts or a relay). It could be wired a few different
ways, as long as the regulator sensing voltage comes from the alternator
output or battery, the regulator is in series with the field coil, and
somehow the field coil gets energized to kick-start the alternator.

Hope this helps.

–John

6

Mark Stephenson wrote:

John,

I think I have the bases covered, but before I fry something here’s how it
ended up. (By the way, when I get this done, I’ll do a complete write up for
anyone else who would like to perform this low-cost (except for time)
conversion.
±--------+
|/|| |++
|V| | || ||| Output Terminal (large nut)
| | | || | ++
[ = [ || |= Regulator Terminal (small Nut)
| | | || |_
|^| | || |_| Ground Terminal (spade)
|/|| |- Field/Brush Terminal (spade)
±--------+

The generator’s Output Terminal originally went to the D terminal on the 120
control box which ran through the regulator, contacts, a couple series
windings and came out at terminal A. I bypassed all of the control box
internals and connected the alternator Output Terminal directly to Terminal
A. Inside the control box, Terminal A is also connected, via another series
winding, to Terminal A1 which powers the headlight switch. I didn’t change
that.

The Regulator Terminal connects to the orange wire on the AMC regulator.
Because the AMC regulator is an opaque epoxy sealed unit, I can’t tell you
any more than the wire colors, but in the AMC car, that wire also connects
to one side of the ignition light. The other side of the light may go to
ground, but since they don’t break down the dashboard circuitry in the AMC
manual, it could just as easily go to battery. In the 120, the ignition
light was connected on one side to the D terminal (where the generator
output was connected) on the 120 control box; and on the other, through the
starter button to the starter solenoid (where I’m guessing it picked up
battery current when the solenoid was not actuated).

The Ground Terminal goes to a black wire on the AMC regulator.

The Field or Brush (depending on the book) Terminal hooks to a dark green
wire on the AMC regulator.

So it looks to me like the Regulator Terminal excites the field, but that
leaves me wondering what the Field/Brush Terminal does. Since it’s not
connected to anything but the regulator, I should be OK … right?.

Mark,

I’d guess you’re right about the regulator terminal exciting the field.
You may have to hook the other side of the warning lamp to +12 in order
for the lamp to light, but the regulator might itself be capable of
supplying the initial current for the field coil. With a voltmeter and
test lamp you ought to be able to pretty easily figure out how the lamp
should be wired. My guess is that the regulator varies the resistance
between the Field/Brush terminal and Ground to adjust the current
through the field coil to achieve the desired output voltage.

Finally, the yellow wire on the AMC regulator goes to the coil, the starter
relay, the fuse box, and the rest of the car, so I’m thinking that’s the
“juice” for the regulator. I have that hooked into the ignition-switch
switched side of the 120 control box – Terminal A3.

Right, and where it senses the output voltage for regulation purposes.

As far as bypassing the ammeter with one wire and the ammeter reading being
incorrect, I don’t think 50 amps max will be carried by one 10 Ga. wire,
will it? One benefit: it might alleviate the problem of too much voltage
through the old 30 amp max ammeter.

You may get some semblance of believable readings. But if you really
need to convert the meter to 60 amps, you could measure the resistance
of the ammeter, and put a resistor of equal value across it. The
resistor will probably be very small in value, and not dissipate much
power, but you need one of adequate power capacity. For example, if the
resistance was 0.1 ohm, a 10 watt resistor would be fine.

Unless you wire the alternator on one side of the meter, and battery on
the other, it’s not going to really show you what is going on.

Good Luck,

–John>

If anyone can see any obvious errors, please let me know – I have $39.99
and/or $16.99 riding on my logic. (That’s a scary thought!)

“Mark 1” Mark Stephenson
1952 XK120 Roadster #673129 (w/XK140 engine and C head)
1958 3.4 Litre Saloon / 1984 XJ6 4.2L / 1985 XJ6 VDP
Jaguar Club of Central Arizona (USA) – Internet Service Provider, TV & Phone | Sparklight

----- Original Message -----
From: “John Loring” <@John_Loring1>
To: xk@jag-lovers.org
Sent: Thursday, December 16, 1999 1:18 PM
Subject: Re: [xk] Alternator Conversion

Mark

I think I can answer a couple of your questions.

Mark Stephenson wrote:

Finally, I want to keep extraneous wires to a minimum. I have the 10 ga.
yellow wire that ran from the generator output to the D terminal on the
RF95, that will now run from the alternator to terminal A. I don’t want
to
fry that wire, and I know the 75 amp Lucas alternators use two 10 ga.
wires
from the alternator, so I was considering a second 10 ga. wire that
would
run from the alternator output to the big battery wire post on the
solenoid.
Anyone see any problems with that?

This will work fine, except your ammeter readings will be incorrect, at
least for charge readings. See below.

Then I just have to connect the American Motors regulator wires to the
proper terminals on the back of the alternator and I should be in
business,
correct?

I’m not sure how the AMC regulator is wired, but one thing to consider
is how the alternator will be ‘excited’. There is usually a terminal on
an alternator that connects to the ignition warning light (charge idiot
light). The other side of the warning lamp is conected to the plus
terminal of the battery. This provides two functions, lighting the lamp
under the right circumstances, and, more importantly, providing a small
current to the alternator field coil until the alternator starts
producing current on its own. Generators don’t need this, but all
except ‘one-wire’ alternators do. Certainly the regulator and
alternator could be designed to provide this in another way.

Assuming that I have figured out everything so far, the only thing I’m
not
sure about is how the alternator ties into the ammeter. Even if someone
has
converted to an alternator with a built-in regulator, I think your
connection method will still apply, because there aren’t that many
options.

Basically, the alternator output should be connected to one side of the
ammeter, the battery should be connected to the other side of the
ammeter. All other electrical loads should be connected directly or
indirectly to the alternator side of the ammeter. The ammeter simply
show whether current is flowing into or out of the battery. No other
current should flow through it, although there may be occasional
instances where a small load is wired on the battery side.

As far as the ignition light goes, I have a little better idea, I think.
There’s a wire that runs from what is called the “regulator terminal” on
the
alternator to the regulator, and on the Gremlin, it also seems to run to
the
ignition light, then to ground. However, I wasn’t sure about the
schematic
because the ignition light was not specifically identified. It was the
only
component, lumped into the dash circuitry, that had a line running from
the
regulator. Does that make sense?

As stated above, there is typically a circuit from the battery positive
terminal, through the warning light, through the field coil, through the
regulator to ground. The alternator output is also internally
connected to the positive side of field coil on most alternators. (But
some Lucas alternators, for example, have an additional external
terminal for this, which must be switched on and off by additional
ignition switch contacts or a relay). It could be wired a few different
ways, as long as the regulator sensing voltage comes from the alternator
output or battery, the regulator is in series with the field coil, and
somehow the field coil gets energized to kick-start the alternator.

Hope this helps.

–John

7

John Loring wrote:

…
You may get some semblance of believable readings. But if you really
need to convert the meter to 60 amps, you could measure the resistance
of the ammeter, and put a resistor of equal value across it. The
resistor will probably be very small in value, and not dissipate much
power, but you need one of adequate power capacity. For example, if the
resistance was 0.1 ohm, a 10 watt resistor would be fine.

Mark,

Whoops, that should have been 100 watt, not 10.

–John

8

Remember, Mark, that you’d be converting a positive-ground car. Swap the primary ignition
wires on the ignition coil to maintain the correct polarity of the high-voltage spark,
when you install the alternator!

All else I’ve heard seems to be OK, in the main.

Best of luck! Keep the old parts and a good record of whatever you do (for the NEXT
guy!).

Larry Schear
Twin Cam, Inc.> John Loring wrote:

…
You may get some semblance of believable readings. But if you really
need to convert the meter to 60 amps, you could measure the resistance
of the ammeter, and put a resistor of equal value across it. The
resistor will probably be very small in value, and not dissipate much
power, but you need one of adequate power capacity. For example, if the
resistance was 0.1 ohm, a 10 watt resistor would be fine.

Mark,

Whoops, that should have been 100 watt, not 10.

–John

This message was sent using Voicenet WebMail.
http://www.voicenet.com/webmail/

9

I hate to put a dampener on the ‘simple alternator’ upgrade–but the wiring
harness for most of our old Jags will be over loaded due to the small wire
size. The generators pretty much max out at 25-30 amps,if you are lucky,
whereas an older style alternator will put out 50 to 60 amps. My newer
Taurus alternator is rated at 120 amps. This will occur if you have had to
crank the starter for awhile or left lights, etc. on. Most
alternator/regulators will put almost or full current output instantly,
depending on motor speed to build the battery voltage up to their settings.
The wire size in most stock Jaguar wire harnesses are not rated for this
current for any length of time. You can compare the wire size attached to
any cars alternators versus your generator wires.
The ammeters have that current going thru them also. This is why the cars
started using idiot lights and voltmeters, not current meters, so this high
current is not fed to anything in the dash.
I must strongly suggest that if you do install an alternator, please use
larger wiring in the entire circuit. I would hate to hear about anyones car
catching on fire due to a long charge time or a regulator going bad.

Larry J
660636

In a message dated 12/16/99 3:11:11 AM Pacific Standard Time,
pjmurray@bechtel.com writes: Mark the only thing I can comment on is that you
can use the ammeter but it will have to be converted to 60+ / -60 reading
this is to take account of the extra umph from the alternator. see Jaguar
World January Issue.>>

10

Larry J.,

I agree about wire overload, but wouldn’t that only apply to the current
running from the alternator to the battery? The draw by electrical
components should be the same whether they are powered by alternator,
generator, or battery alone, I would think. Besides, nowadays all the fuses
are very low amperage – I think 20A in US terms is about the max, but most
are 5 and 10. Double those and you have the rough Lucas equivalents. All the
lines in the 120 are fused with either 35A (17.5A US) or 50A (25A US), which
means the 120 wires will have to carry more current longer before a fuse
blows.

The 20 amp Lucas generator fed the regulator via a 10 or 12 ga. line. I
added a second 10 ga. line, which I was going to feed directly to the
battery terminal on the starter solenoid. However, at the advice of some on
the list, I decided to run the new line through the ammeter and a resistor,
so that my ammeter reads amps/2. My XJ6 with a 75 amp Lucas alternator uses
two 10 ga. lines from the alternator to the battery feed, so I think a 10
and a 12 or two 10s (whichever) should handle the current from the 55 amp
Motorola alternator.

If you think there is still a danger, let me know. I’ll accept all input.

Here’s how things are progressing…

Things are wired, the batteries are reversed (but not connected). I cleaned
the gauges and painted the bezels.

NOTE: Do NOT clean the painted face of a gauge with Windex. I did that to
the ammeter and the white markings came off. I stopped as soon as I realized
it, but it seriously faded the markings. I am no artist, but I took some
off-white latex paint, and a very fine brush that I had, and redrew the
numbers and markings. It was very tedious, but the gauge looks good to me
until I get closer than about six inches. Then it looks like someone
hand-painted the markings. Oh well.

I think all I need to do now is to find the right size belt since the
generator pulley was bigger than the alternator one, reverse the aftermarket
fuel pump wires, or perhaps return the Lucas pump to it’s rightful place,
apparently that doesn’t need reversed. I need to reconnect the ammeter, and
reconnect the battery.

Not trusting that I’ve done everything properly, I’m considering first
making the connection through a 35 amp in-line fuse, with nothing turned on.
If that works, then I’ll try the ignition – just turn it on. My petrol
gauge has not been working, although it did for a day or so at one point, so
I’m pretty sure it’s electrical as opposed to something mechanical like a
sunk float. I’d like to troubleshoot that with the 35 amp fuse in place in
case I touch the wrong thing. I’d also like to see if my dash lights are
working properly; some gauges are quite dim.

Am I taking caution a little too far, or is that the prudent thing to do?

Anyway, then I’ll put the whole thing back together and go for a drive.
(Arizona living is wonderful this time of year!)

Final report and complete installation instruction coming soon, if all goes
well.

“Mark 1” Mark Stephenson
1952 XK120 Roadster #673129 (w/XK140 engine and C head)
1958 3.4 Litre Saloon / 1984 XJ6 4.2L / 1985 XJ6 VDP
Jaguar Club of Central Arizona (USA) – Internet Service Provider, TV & Phone | Sparklight Original Message -----
From: XK120@aol.com
To: xk@jag-lovers.org
Sent: Thursday, December 16, 1999 9:40 PM
Subject: Re: [xk] Alternator Conversion

I hate to put a dampener on the ‘simple alternator’ upgrade–but the
wiring
harness for most of our old Jags will be over loaded due to the small wire
size. The generators pretty much max out at 25-30 amps,if you are lucky,
whereas an older style alternator will put out 50 to 60 amps. My newer
Taurus alternator is rated at 120 amps. This will occur if you have had
to
crank the starter for awhile or left lights, etc. on. Most
alternator/regulators will put almost or full current output instantly,
depending on motor speed to build the battery voltage up to their
settings.
The wire size in most stock Jaguar wire harnesses are not rated for this
current for any length of time. You can compare the wire size attached to
any cars alternators versus your generator wires.
The ammeters have that current going thru them also. This is why the cars
started using idiot lights and voltmeters, not current meters, so this
high
current is not fed to anything in the dash.
I must strongly suggest that if you do install an alternator, please use
larger wiring in the entire circuit. I would hate to hear about anyones
car
catching on fire due to a long charge time or a regulator going bad.

Larry J
660636

In a message dated 12/16/99 3:11:11 AM Pacific Standard Time,
pjmurray@bechtel.com writes: Mark the only thing I can comment on is that
you
can use the ammeter but it will have to be converted to 60+ / -60 reading
this is to take account of the extra umph from the alternator. see Jaguar
World January Issue.

11

In a message dated 12/16/99 10:36:17 PM Pacific Standard Time,
marks@starlink.com writes:

<< I agree about wire overload, but wouldn’t that only apply to the current
running from the alternator to the battery? The draw by electrical
components should be the same whether they are powered by alternator,
generator, or battery alone, I would think. Besides, nowadays all the fuses
are very low amperage – I think 20A in US terms is about the max, but most
are 5 and 10. Double those and you have the rough Lucas equivalents. All the
lines in the 120 are fused with either 35A (17.5A US) or 50A (25A US), which
means the 120 wires will have to carry more current longer before a fuse
blows.

Yes, you are partially correct. The ammeter leads in the dash will also have
to carry the full current. You will have to reverse the leads to the ammeter
to read the proper charge/discharge. I am not sure whether you will have to
change the fuel gage, but I would think so. Haven’t ever reversed the
polarity. The screw posts on the ammeter will just be able to handle two 10
ga wires. Watch where you place that resistor, it will get HOT with full
current.
The newer cars have smaller fuses than the old Jags because they fuse almost
every individual item. If you look at the wires that feed the fuse block,
you will see they are pretty large. The good thing is, the Jags just don’t
have that many electrical items so that load is smaller, thus the few smaller
value fuses.

May the Motorola gods smile in your favor and not envoke the rath of Lucas.
Larry J

12

Warning

I’ve been observing this thread with interest and curious where it will end
up.A OK but::
Do NOT hook up the clock or you risk a fire with the reversed polarity.

LOJ

doc----- Original Message -----
From: XK120@aol.com
To: xk@jag-lovers.org
Sent: Friday, December 17, 1999 1:43 AM
Subject: Re: [xk] Alternator Conversion

In a message dated 12/16/99 10:36:17 PM Pacific Standard Time,
marks@starlink.com writes:

<< I agree about wire overload, but wouldn’t that only apply to the
current
running from the alternator to the battery? The draw by electrical
components should be the same whether they are powered by alternator,
generator, or battery alone, I would think. Besides, nowadays all the
fuses
are very low amperage – I think 20A in US terms is about the max, but
most
are 5 and 10. Double those and you have the rough Lucas equivalents. All
the
lines in the 120 are fused with either 35A (17.5A US) or 50A (25A US),
which
means the 120 wires will have to carry more current longer before a fuse
blows.

Yes, you are partially correct. The ammeter leads in the dash will also
have
to carry the full current. You will have to reverse the leads to the
ammeter
to read the proper charge/discharge. I am not sure whether you will have
to
change the fuel gage, but I would think so. Haven’t ever reversed the
polarity. The screw posts on the ammeter will just be able to handle two
10
ga wires. Watch where you place that resistor, it will get HOT with full
current.
The newer cars have smaller fuses than the old Jags because they fuse
almost
every individual item. If you look at the wires that feed the fuse block,
you will see they are pretty large. The good thing is, the Jags just
don’t
have that many electrical items so that load is smaller, thus the few
smaller
value fuses.

May the Motorola gods smile in your favor and not envoke the rath of
Lucas.
Larry J

13

Thanks, Doc,

The clock didn’t work anyway.

I know they sell quartz replacement movements. Does anyone know if they are
polarity sensitive or available in + or - ground?

“Mark 1” Mark Stephenson
1952 XK120 Roadster #673129 (w/XK140 engine and C head)
1958 3.4 Litre Saloon / 1984 XJ6 4.2L / 1985 XJ6 VDP
Jaguar Club of Central Arizona (USA) – Internet Service Provider, TV & Phone | Sparklight Original Message -----
From: “docsjags” doc@docsjags.com
To: xk@jag-lovers.org
Sent: Friday, December 17, 1999 12:19 AM
Subject: Re: [xk] Alternator Conversion

Warning

I’ve been observing this thread with interest and curious where it will
end
up.A OK but::
Do NOT hook up the clock or you risk a fire with the reversed polarity.

LOJ

doc

----- Original Message -----
From: XK120@aol.com
To: xk@jag-lovers.org
Sent: Friday, December 17, 1999 1:43 AM
Subject: Re: [xk] Alternator Conversion

In a message dated 12/16/99 10:36:17 PM Pacific Standard Time,
@Mark_Stephenson4 writes:

<< I agree about wire overload, but wouldn’t that only apply to the
current
running from the alternator to the battery? The draw by electrical
components should be the same whether they are powered by alternator,
generator, or battery alone, I would think. Besides, nowadays all the
fuses
are very low amperage – I think 20A in US terms is about the max, but
most
are 5 and 10. Double those and you have the rough Lucas equivalents.
All
the
lines in the 120 are fused with either 35A (17.5A US) or 50A (25A US),
which
means the 120 wires will have to carry more current longer before a
fuse
blows.

Yes, you are partially correct. The ammeter leads in the dash will also
have
to carry the full current. You will have to reverse the leads to the
ammeter
to read the proper charge/discharge. I am not sure whether you will
have
to
change the fuel gage, but I would think so. Haven’t ever reversed the
polarity. The screw posts on the ammeter will just be able to handle
two
10
ga wires. Watch where you place that resistor, it will get HOT with
full
current.
The newer cars have smaller fuses than the old Jags because they fuse
almost
every individual item. If you look at the wires that feed the fuse
block,
you will see they are pretty large. The good thing is, the Jags just
don’t
have that many electrical items so that load is smaller, thus the few
smaller
value fuses.

May the Motorola gods smile in your favor and not envoke the rath of
Lucas.
Larry J

14

Mark,

My apologies for entering this discussion a little late.  I bought an

XK140 about six months ago which had been converted by the previous owner to
an alternator in the early '70’s. He must have done the same search you
did, because he came up with a similar choice: Motorola alternator model
no. A12PX550 (positive ground) and regulator model no. TVR12X1. He was
vague on the details, but said the system had worked fine for many years,
then stopped functioning after a winter in storage. When I checked the
system out, I found that the only thing wrong was a corroded connection
between the alternator and the isolation diodes mounted on the rear.
I was also concerned about the amount of current the alternator could
put out compared to the generator. However, that has not been a problem.
With the engine running after the battery has been fairly heavily drained,
the maximum current flow indicated on the dash ammeter is about 15 amps.
Under normal running conditions, it bounces around zero, just as my previous
XK’s with generators did, and this doesn’t change, even when I have every
electric item I can think of on (lights and windshield wipers running,
heater on, horn blowing). I don’t think the XK has enough electrical
accessories to get you into trouble unless a short developes (and then you
should blow a fuse). What I DO notice that’s different is that even at idle
with the lights on, the ammeter is at zero or on the plus side, a pleasant
change from the generator.
I’m not sure if the PO installed a resistor to protect the ammeter, as
has been suggested, but I suspect he did not. If it helps, the indicated
current draw with my lights on and the engine off is about 15 amps, but I
can’t remember what the readings were for my previous XK’s.

Hope this helps give you the courage to throw the switch,
Jon
55 XK140FHC----- Original Message -----
From: Mark Stephenson marks@starlink.com
To: xk@jag-lovers.org
Sent: Thursday, December 16, 1999 5:26 AM
Subject: Re: [xk] Alternator Conversion

Here is the latest on the alternator conversion:

My local AutoZone was kind enough to let me peruse their alternator
inventory in search of one with a similar configuration to the Lucas
generator. After going through about 20, I found a 52 (or 55, depending on
where you look) amp Motorola alternator with the exact same pulley
placement. In case anyone is interested it is AutoZone part number 7429.
It
will bolt on the front of the generator bracket just like the generator,
with a 3/8x8" bolt through the alternator, the bracket and steel tube
(for
rigidity) and out the back. The alternator was a mere $39.99 + $15.00
core.
The only drawback is that it doesn’t have a built in regulator, so I had
to
track one of those down. Again AutoZone was very helpful, helping me
search
the pages, looking for the number amidst all the generator numbers listed.
I
told them to take care of other customers and I’d continue the search and
much to my surprise, and theirs, I discovered a listing of applications by
alternator number at the back of their book. That’s how I discovered, much
to my chagrin, that it was early 70s American Motors. They had a
regulator,
but I wasn’t sure how it was going to work, so I held off on that.

Then I went to the library, in disguise because I didn’t want anyone to
recognize me as I checked out books for early 70s Gremlins, Hornets, and
Matadors. (How embarrassing!) After learning how the regulator fit into
the
scheme of things, I returned to AutoZone for the VR727 regulator,
US$16.99.

Both have lifetime warranties.

After examining Gremlin and XK120 (I hate to use those two words together
in
the same sentence.) wiring diagrams in detail, and while it’s still fresh
in
my mind (before I head off to bed), I’m hoping some of the electrical
geniuses on the list can verify my theories regarding alternators vs.
generators.

With a generator and a regulator, the regulator controls the output of the
generator directly by adjusting the voltage and amperage before it flows
to
the battery. As I see it, the raw generator output doesn’t change (unless
the field strength is adjusted to control output). The regulator for an
alternator, on the other hand, controls the alternator so it only puts out
the amperage needed to power the electrical system and charge the battery.

Am I correct so far?

If so, I’ll continue on my mad dash to electrical nirvana…

I want to keep as many of the original components with the car in case a
miracle happens and the original engine turns up. I have the RF95 Control
Box, which includes a terminal block and some fuses. I’ve figured out what
goes where and why, and rather than reinvent the wheel, I might as well
use
the terminal block feature of the control box. It seems to me that I’d
have
to disable the regulator part of the box, though, since I’ll be powering
directly to the battery from the alternator.

Am I still on the right track?

It seems that to adapt the RF95, all I would need to do is disconnect the
ground wire from terminal E; remove the field wire from terminal F, since
I’m going to use that wire for the new regulator; and move the generator
(now alternator) output wire from terminal D to terminal A. At that point
I
would have a really impressive looking terminal block, right?

Finally, I want to keep extraneous wires to a minimum. I have the 10 ga.
yellow wire that ran from the generator output to the D terminal on the
RF95, that will now run from the alternator to terminal A. I don’t want to
fry that wire, and I know the 75 amp Lucas alternators use two 10 ga.
wires
from the alternator, so I was considering a second 10 ga. wire that would
run from the alternator output to the big battery wire post on the
solenoid.
Anyone see any problems with that?

Then I just have to connect the American Motors regulator wires to the
proper terminals on the back of the alternator and I should be in
business,
correct?

Assuming that I have figured out everything so far, the only thing I’m not
sure about is how the alternator ties into the ammeter. Even if someone
has
converted to an alternator with a built-in regulator, I think your
connection method will still apply, because there aren’t that many
options.

As far as the ignition light goes, I have a little better idea, I think.
There’s a wire that runs from what is called the “regulator terminal” on
the
alternator to the regulator, and on the Gremlin, it also seems to run to
the
ignition light, then to ground. However, I wasn’t sure about the schematic
because the ignition light was not specifically identified. It was the
only
component, lumped into the dash circuitry, that had a line running from
the
regulator. Does that make sense?

I know I’ve asked a lot of questions, but I hope that the listing of the
alternator and regulator part numbers will be some miniscule repayment for
the information I have and will continue to receive from the great minds
of
the list.

“Mark 1” Mark Stephenson
1952 XK120 Roadster #673129 (w/XK140 engine and C head)
1958 3.4 Litre Saloon / 1984 XJ6 4.2L / 1985 XJ6 VDP
Jaguar Club of Central Arizona (USA) – Internet Service Provider, TV & Phone | Sparklight

----- Original Message -----
From: “Mark Stephenson” marks@starlink.com
To: “XK Lovers” xk@jag-lovers.org
Sent: Sunday, December 12, 1999 9:46 PM
Subject: [xk] Alternator Conversion

Since my generator died, I decided to convert to negative ground and an
alternator. I’ll save the generator for future generations. In the
meantime,
has anyone found an alternator which installs easily, without making a
new
bracket?

I have found an early 70s American Motors alternator (52 amp) which has
the
correct offset from the back of the front pivot bracket. The only
problem
is
that it doesn’t have a built-in regulator, which would simplify things
tremendously since neither the alternator nor the regulator come with
instructions or a wiring diagram.

Thanks in advance,

“Mark 1” Mark Stephenson
1952 XK120 Roadster #673129 (w/XK140 engine and C head)
1958 3.4 Litre Saloon / 1984 XJ6 4.2L / 1985 XJ6 VDP
Jaguar Club of Central Arizona (USA) – Internet Service Provider, TV & Phone | Sparklight

NetZero - Defenders of the Free World
Get your FREE Internet Access and Email at
http://www.netzero.net/download/index.html

15

Most electronic clocks are polarity-sensitive, Mark. Designed for negative ground
(prevailing implementation), but might be reversible, if internals are ‘floating’ with
respect to the case.

I’m wondering why Doc said the original clock would be affected by the polarity; it’s a
solenoid-operated mechanical clock, wherein the solenoid pulls an armature againist a
spring until a contact is broken, and the spring provides energy to run the clock until
the solenoid contacts again close - should be polarity-insensitive. Take your old clock
apart - the mechanism is quite ingenious!

Did you ever acquire an XK-120 / Mark VII shop manual? One was on eBay the other night,
and I think I sent you an alert about it.

Geting cold here!

Cheers!

Larry Schear
Twin Cam, Inc.> Thanks, Doc,

The clock didn’t work anyway.

I know they sell quartz replacement movements. Does anyone know if they are
polarity sensitive or available in + or - ground?

“Mark 1” Mark Stephenson
1952 XK120 Roadster #673129 (w/XK140 engine and C head)
1958 3.4 Litre Saloon / 1984 XJ6 4.2L / 1985 XJ6 VDP
Jaguar Club of Central Arizona (USA) – Internet Service Provider, TV & Phone | Sparklight

----- Original Message -----
From: “docsjags” doc@docsjags.com
To: xk@jag-lovers.org
Sent: Friday, December 17, 1999 12:19 AM
Subject: Re: [xk] Alternator Conversion

Warning

I’ve been observing this thread with interest and curious where it will
end
up.A OK but::
Do NOT hook up the clock or you risk a fire with the reversed polarity.

LOJ

doc

----- Original Message -----
From: XK120@aol.com
To: xk@jag-lovers.org
Sent: Friday, December 17, 1999 1:43 AM
Subject: Re: [xk] Alternator Conversion

In a message dated 12/16/99 10:36:17 PM Pacific Standard Time,
marks@starlink.com writes:

<< I agree about wire overload, but wouldn’t that only apply to the
current
running from the alternator to the battery? The draw by electrical
components should be the same whether they are powered by alternator,
generator, or battery alone, I would think. Besides, nowadays all the
fuses
are very low amperage – I think 20A in US terms is about the max, but
most
are 5 and 10. Double those and you have the rough Lucas equivalents.
All
the
lines in the 120 are fused with either 35A (17.5A US) or 50A (25A US),
which
means the 120 wires will have to carry more current longer before a
fuse
blows.

Yes, you are partially correct. The ammeter leads in the dash will also
have
to carry the full current. You will have to reverse the leads to the
ammeter
to read the proper charge/discharge. I am not sure whether you will
have
to
change the fuel gage, but I would think so. Haven’t ever reversed the
polarity. The screw posts on the ammeter will just be able to handle
two
10
ga wires. Watch where you place that resistor, it will get HOT with
full
current.
The newer cars have smaller fuses than the old Jags because they fuse
almost
every individual item. If you look at the wires that feed the fuse
block,
you will see they are pretty large. The good thing is, the Jags just
don’t
have that many electrical items so that load is smaller, thus the few
smaller
value fuses.

May the Motorola gods smile in your favor and not envoke the rath of
Lucas.
Larry J

This message was sent using Voicenet WebMail.
http://www.voicenet.com/webmail/

16

Guy Broad or XK s Unlmtd.

doc----- Original Message -----
From: Mark Stephenson marks@starlink.com
To: xk@jag-lovers.org
Sent: Friday, December 17, 1999 10:17 AM
Subject: Re: [xk] Alternator Conversion

Thanks, Doc,

The clock didn’t work anyway.

I know they sell quartz replacement movements. Does anyone know if they
are
polarity sensitive or available in + or - ground?

“Mark 1” Mark Stephenson
1952 XK120 Roadster #673129 (w/XK140 engine and C head)
1958 3.4 Litre Saloon / 1984 XJ6 4.2L / 1985 XJ6 VDP
Jaguar Club of Central Arizona (USA) – Internet Service Provider, TV & Phone | Sparklight

----- Original Message -----
From: “docsjags” <@doc1>
To: xk@jag-lovers.org
Sent: Friday, December 17, 1999 12:19 AM
Subject: Re: [xk] Alternator Conversion

Warning

I’ve been observing this thread with interest and curious where it will
end
up.A OK but::
Do NOT hook up the clock or you risk a fire with the reversed polarity.

LOJ

doc

----- Original Message -----
From: XK120@aol.com
To: xk@jag-lovers.org
Sent: Friday, December 17, 1999 1:43 AM
Subject: Re: [xk] Alternator Conversion

In a message dated 12/16/99 10:36:17 PM Pacific Standard Time,
marks@starlink.com writes:

<< I agree about wire overload, but wouldn’t that only apply to the
current
running from the alternator to the battery? The draw by electrical
components should be the same whether they are powered by alternator,
generator, or battery alone, I would think. Besides, nowadays all the
fuses
are very low amperage – I think 20A in US terms is about the max,
but
most
are 5 and 10. Double those and you have the rough Lucas equivalents.
All
the
lines in the 120 are fused with either 35A (17.5A US) or 50A (25A
US),
which
means the 120 wires will have to carry more current longer before a
fuse
blows.

Yes, you are partially correct. The ammeter leads in the dash will
also
have
to carry the full current. You will have to reverse the leads to the
ammeter
to read the proper charge/discharge. I am not sure whether you will
have
to
change the fuel gage, but I would think so. Haven’t ever reversed the
polarity. The screw posts on the ammeter will just be able to handle
two
10
ga wires. Watch where you place that resistor, it will get HOT with
full
current.
The newer cars have smaller fuses than the old Jags because they fuse
almost
every individual item. If you look at the wires that feed the fuse
block,
you will see they are pretty large. The good thing is, the Jags just
don’t
have that many electrical items so that load is smaller, thus the few
smaller
value fuses.

May the Motorola gods smile in your favor and not envoke the rath of
Lucas.
Larry J

17

Jon,

>Motorola alternator model no. A12PX550 (positive ground) and >regulator model no. TVR12X1..."

Motorola sold two alternators during the early seventies, a 35A and a 55A. I
have learned that the 55A was used on cars with A/C. It would seem to me, if
that number means anything, that you have the 55A model, but it could be the
35A which would have been within the tolerances of the existing electrical
system.

What kind of needle reaction do you get when the system charges after a deep
discharge? Does the needle peg?

Larry,

I had the clock apart, but couldn’t discern where the problem was.
Everything seemed to be working right, and I could manually rotate the
balance wheel, which would swing back and forth a few times before stopping.
I’d heard stories of people going to great lengths to fix their clocks, only
to have them work for a week or so and stop again. So I decided not to put a
lot of time into it.

I was fascinated with the clock in an old TR4 (or was it a '59 MB 190 “the
Bulldog”). Maybe this is a more standard configuration, but it had a spring
and a couple contacts. As the spring wound down the contacts would come
closer and closer together until they touched. That would cause a small
motor to spin and wind the spring, until the tension reached the point that
the contacts separated. The motor would run for about 2-3 seconds in a burst
about every half hour or so as I recall.

I managed to buy a shop manual in very good condition, Wherrett’s “Jaguar
XK”, the JEC’s XJ6 restoration book, the Autopress XK & Mk VII-IX book, Mike
Lawrence’s “Essential Jaguar XK”, and Practical Classics “on XK Jaguar
Restoration” for $100. A guy in the club had both an XJ6 and a 150 and sold
both, but still had the books. It was quite a haul.

He was the guy who let me and my son stay overnight at his place after the
generator failed. In that regard it really paid off.

“Mark 1” Mark Stephenson
1952 XK120 Roadster #673129 (w/XK140 engine and C head)
1958 3.4 Litre Saloon / 1984 XJ6 4.2L / 1985 XJ6 VDP
Jaguar Club of Central Arizona (USA) – Internet Service Provider, TV & Phone | Sparklight Original Message -----
From: twincam@voicenet.com
To: xk@jag-lovers.org
Sent: Friday, December 17, 1999 8:41 AM
Subject: Re: [xk] Alternator Conversion

Most electronic clocks are polarity-sensitive, Mark. Designed for
negative ground
(prevailing implementation), but might be reversible, if internals are
‘floating’ with
respect to the case.

I’m wondering why Doc said the original clock would be affected by the
polarity; it’s a
solenoid-operated mechanical clock, wherein the solenoid pulls an armature
againist a
spring until a contact is broken, and the spring provides energy to run
the clock until
the solenoid contacts again close - should be polarity-insensitive. Take
your old clock
apart - the mechanism is quite ingenious!

Did you ever acquire an XK-120 / Mark VII shop manual? One was on eBay
the other night,
and I think I sent you an alert about it.

Geting cold here!

Cheers!

Larry Schear
Twin Cam, Inc.

18

Mark,

Motorola sold two alternators during the early seventies, a 35A and a 55A.
I
have learned that the 55A was used on cars with A/C. It would seem to me,
if
that number means anything, that you have the 55A model, but it could be
the
35A which would have been within the tolerances of the existing electrical
system.

It is the 55A model.

What kind of needle reaction do you get when the system charges after a
deep
discharge? Does the needle peg?

I’ve never had a truly deep discharge, so I can’t tell you what would
happen. The highest reading I’ve seen is a very transient (1-2 seconds)20A
on the 30A scale, with a more prolonged time at 15A. I have a service
manual the Motorola HA series alternators which has an output graph for the
55A models. At 60 deg F it shows an output of 20A at a shaft speed of about
1600 RPM, 30A at about 1800 RPM, and 40A at about 2200 RPM, so in a deep
discharge situation, you could conceivably peg the needle if you immediately
drove the car at highway speeds, but should not encounter problems if you
let it idle for a short time first.

Jon__________________________________________
NetZero - Defenders of the Free World
Get your FREE Internet Access and Email at
http://www.netzero.net/download/index.html

19

Mark,

Remember that the Ammeter reads the current from the alternator to the
battery, and not from the alternator to the lights, wipers, horns, radio,
etc. So the load makes no difference to the Ammeter reading; it is only
affected by the state of charge of the battery.

25 Amps is an adequate charge rate for a somewhat discharged battery. Much
more than that will generally have undesired effects, such as boiling the
electrolyte and warping the plates.

I think you should proclaim the transplant a success!

Mike Eck

Mike,

I agree, but even when the battery was somewhat discharged, as when I first
started it after sitting for two weeks, testing headlights, dash lights,
and
other circuits, it still didn’t feed more than about 25 amps. The needle
would actually fly up and bounce off the peg, then stabilize at about 25
amps.

snip-----Original Message-----
From: Mark Stephenson marks@starlink.com

20

Excellent! Should I dispense with the second wire?

BTW, thanks for your excellent explanation of alternators vs. generators. It
was enlightening.

Mark----- Original Message -----
From: “Michael Eck” MichaelEck@att.net
To: xk@jag-lovers.org
Sent: Sunday, December 26, 1999 9:13 AM
Subject: Re: [xk] Alternator Conversion

Mark,

Remember that the Ammeter reads the current from the alternator to the
battery, and not from the alternator to the lights, wipers, horns, radio,
etc. So the load makes no difference to the Ammeter reading; it is only
affected by the state of charge of the battery.

25 Amps is an adequate charge rate for a somewhat discharged battery.
Much
more than that will generally have undesired effects, such as boiling the
electrolyte and warping the plates.

I think you should proclaim the transplant a success!

Mike Eck

-----Original Message-----
From: Mark Stephenson <@Mark_Stephenson4>

Mike,

I agree, but even when the battery was somewhat discharged, as when I
first
started it after sitting for two weeks, testing headlights, dash lights,
and
other circuits, it still didn’t feed more than about 25 amps. The needle
would actually fly up and bounce off the peg, then stabilize at about 25
amps.

snip