[E-Type] Ignition Idiot light?

E-Type
1

The Ignition Idiot Light: What function does it serve?

I ask because the following thing occurred Saturday night…

I drove the car into town for dinner with my wife* and since the
speedo is removed (being fixed at Nisonger as we speak) I noted an
intermittent glowing around my knees. Upon further investigation it
turned out the ignition idiot light was just barely coming on, at
intervals… like a kid playing with a rheostat. (we all did that
as kids, right? see how low we could go before the light went out.)

Who knows how long this has been going on, as I hardly ever, almost
never, drive the car at night. The faint light is probably not even
visible through the speedo’s light lens. Certainly not in daylight. I
think I was only able to see it due to being in complete darkness and
the bulb itself was bare and hanging down under the dashboard. I did
not have any dash lights on at the time, and I did not notice it
until we were on a very dark stretch of forested road.

Is there some electrical problem somewhere? If so, what should I be
looking for?

*We were having something of a “heat wave” here in the Pacific
Northwest this weekend. The wife and I were taking advantage of our
kids being gone to do some housepainting… I managed to repaint the
front hallway, the kitchen, dining room, and another hallway. Our
reward was a late dinner on Saturday night in the one nice restaurant
we have here in Arlington. We enjoyed a wonderful dinner while
sitting outside, like being in a European cafe. They only have two
outdoor tables and every person that came outside after their
dinner commented on how smart we were to sit outside, as the interior
of the restaurant was very hot. The ride in the E-type served as a
nice dessert. =) Though as always, it messed up my wife’s hair.

I missed the ABFM, but did get a ton of work done, and enjoyed a nice
night out with the wife.–
–chuck goolsbee
65ots, 1E10715
arlington, wa, usa

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

2

In reply to a message from chuck goolsbee sent Mon 26 Jul 2004:

Chuck,
Ours will sometimes have just a faint glow, barely
visible at idle at night. Been that way a few years. Still
the same after the charge circ stopped working when a brush
stopped making contact. Battery charges fine and the
charging voltage is o.k. If the charge circ is failing the
light will brighten.
Of course, we could just presume that a romantic drive
with your wife after a lovely dinner was causing a higher
level of excitation (down around your kness???)

Andrew–
The original message included these comments:

Is there some electrical problem somewhere? If so, what should I be
looking for?
*We were having something of a ‘‘heat wave’’ here in the Pacific
Northwest this weekend. The wife and I were taking advantage of our

–
1968 3.8S
Zurich, Switzerland
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

3

In reply to a message from chuck goolsbee sent Mon 26 Jul 2004:

Chuck,

Unless I’m mistaken (probably), the ignition warning lamp on your
car actually operates from an oil pressure switch in the block.

I’m not familiar with l.h.d. cars, or when the various changes to
the electrical systems were made, but certainly on my 64 4.2 rhd
car, the ignition warning lamp has absolutely no connection with
the electrical charging system on the car.

Did it only come on at low engine speeds?

Regards,

Garth.–
The original message included these comments:

intermittent glowing around my knees. Upon further investigation it
turned out the ignition idiot light was just barely coming on, at
intervals… like a kid playing with a rheostat. (we all did that
Is there some electrical problem somewhere? If so, what should I be
looking for?

–
Dr.G
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

4

There is a relay (4AW) that controls that light, Sounds like it is bad. If
so, do yourself a favor and replace it with a solid state equivalent that is
available from CoolCat (www.coolcatcorp.com)

Dennis Eklof-----Original Message-----
From: owner-e-type@jag-lovers.org [mailto:owner-e-type@jag-lovers.org]On
Behalf Of chuck goolsbee
Sent: Monday, July 26, 2004 1:10 PM
To: e-type@jag-lovers.org
Subject: [E-Type] Ignition Idiot light?

The Ignition Idiot Light: What function does it serve?

I ask because the following thing occurred Saturday night…

I drove the car into town for dinner with my wife* and since the
speedo is removed (being fixed at Nisonger as we speak) I noted an
intermittent glowing around my knees. Upon further investigation it
turned out the ignition idiot light was just barely coming on, at
intervals… like a kid playing with a rheostat. (we all did that
as kids, right? see how low we could go before the light went out.)

Who knows how long this has been going on, as I hardly ever, almost
never, drive the car at night. The faint light is probably not even
visible through the speedo’s light lens. Certainly not in daylight. I
think I was only able to see it due to being in complete darkness and
the bulb itself was bare and hanging down under the dashboard. I did
not have any dash lights on at the time, and I did not notice it
until we were on a very dark stretch of forested road.

Is there some electrical problem somewhere? If so, what should I be
looking for?

*We were having something of a “heat wave” here in the Pacific
Northwest this weekend. The wife and I were taking advantage of our
kids being gone to do some housepainting… I managed to repaint the
front hallway, the kitchen, dining room, and another hallway. Our
reward was a late dinner on Saturday night in the one nice restaurant
we have here in Arlington. We enjoyed a wonderful dinner while
sitting outside, like being in a European cafe. They only have two
outdoor tables and every person that came outside after their
dinner commented on how smart we were to sit outside, as the interior
of the restaurant was very hot. The ride in the E-type served as a
nice dessert. =) Though as always, it messed up my wife’s hair.

I missed the ABFM, but did get a ton of work done, and enjoyed a nice
night out with the wife.

–
–chuck goolsbee
65ots, 1E10715
arlington, wa, usa

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

5

On my 66 it is controlled by an oil pressure switch.

tom

[Original Message]
From: Dennis Eklof dennis.eklof@verizon.net
To: e-type@jag-lovers.org
Date: 7/26/04 6:21:29 PM
Subject: RE: [E-Type] Ignition Idiot light?

There is a relay (4AW) that controls that light, Sounds like it is bad.
If
so, do yourself a favor and replace it with a solid state equivalent that
is
available from CoolCat (www.coolcatcorp.com)

Dennis Eklof

-----Original Message-----
From: owner-e-type@jag-lovers.org [mailto:owner-e-type@jag-lovers.org]On
Behalf Of chuck goolsbee
Sent: Monday, July 26, 2004 1:10 PM
To: e-type@jag-lovers.org
Subject: [E-Type] Ignition Idiot light?

The Ignition Idiot Light: What function does it serve?

I ask because the following thing occurred Saturday night…

I drove the car into town for dinner with my wife* and since the
speedo is removed (being fixed at Nisonger as we speak) I noted an
intermittent glowing around my knees. Upon further investigation it
turned out the ignition idiot light was just barely coming on, at
intervals… like a kid playing with a rheostat. (we all did that
as kids, right? see how low we could go before the light went out.)

Who knows how long this has been going on, as I hardly ever, almost
never, drive the car at night. The faint light is probably not even
visible through the speedo’s light lens. Certainly not in daylight. I
think I was only able to see it due to being in complete darkness and
the bulb itself was bare and hanging down under the dashboard. I did
not have any dash lights on at the time, and I did not notice it
until we were on a very dark stretch of forested road.

Is there some electrical problem somewhere? If so, what should I be
looking for?

*We were having something of a “heat wave” here in the Pacific
Northwest this weekend. The wife and I were taking advantage of our
kids being gone to do some housepainting… I managed to repaint the
front hallway, the kitchen, dining room, and another hallway. Our
reward was a late dinner on Saturday night in the one nice restaurant
we have here in Arlington. We enjoyed a wonderful dinner while
sitting outside, like being in a European cafe. They only have two
outdoor tables and every person that came outside after their
dinner commented on how smart we were to sit outside, as the interior
of the restaurant was very hot. The ride in the E-type served as a
nice dessert. =) Though as always, it messed up my wife’s hair.

I missed the ABFM, but did get a ton of work done, and enjoyed a nice
night out with the wife.

–
–chuck goolsbee
65ots, 1E10715
arlington, wa, usa

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

6

There is a relay (4AW) that controls that light,

Do you mean 3AW?

Sounds like it is bad.

Ray L wrote me offlist and said the faint glow was “normal” but a bright one is cause for concern.

If
so, do yourself a favor and replace it with a solid state equivalent that is
available from CoolCat (www.coolcatcorp.com)

Actually, I think that is already the case. I never could find a 3AW relay in my car as it was described in the manuals and by others here on the list. But there is an odd extra bit of hardware inside my dash:

http://chuck.forest.net/jag/saturdaydrive/SaturdayDrive-Pages/Image17.html

It doesn’t look like the CoolCat model though… at least from this angle:

http://coolcatcorp.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=SS3AW&Category_Code=EL

Always a mystery these things…–
–chuck goolsbee
65ots, 1E10715
arlington, wa, usa

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

7

In reply to a message from chuck goolsbee sent Mon 26 Jul 2004:

Chuck,
Ours will sometimes have just a faint glow, barely
visible at idle at night. Been that way a few years. Still
the same after the charge circ stopped working when a brush
stopped making contact. Battery charges fine and the
charging voltage is o.k. If the charge circ is failing the
light will brighten.

My battery is charging fine.

I think you have come closest to actually answering my question then:
The light glows bright if the charging circuit fails (or is failing).

Of course, we could just presume that a romantic drive

with your wife after a lovely dinner was causing a higher
level of excitation (down around your kness???)

Well, it could have been that I guess. =)

It has been a nice couple of weeks around here without kids!–
–chuck goolsbee
65ots, 1E10715
arlington, wa, usa

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

8

The only purpose of the light is to warn you that the key is in
the “on” position, but the engine isn’t running.

     Catch me up. When last you reported, you had a Lucas, but you were

going to switch to a GMtachidenso or something like that.

     I'm assuming (always dangerous) that your voltmeter is reading

over 13V. If not, then look for an alternator or VR problem.

     If you still have the original Lucas setup with a 3AW, the light

usually means that one phase of your alternator’s three phase output is
low. Most likely, the connector on the alternator’s AL terminal is loose
(if so equipped).Otherwise, the intermittent light could be due to any
number of conditions, such as carbonized slip rings, a bad voltage
regulator (never happens, right?), or a bad relay. On older cars, the light
is triggered by an oil pressure switch rather than a 3AW relay, and the
sender could be bad.

     If you've switched to a modern alternator, the light provides

“boot” current to the alternator when you start the car. One side of the
bulb connects to the battery bus, the other to the alternator’s internal
VR. When you are starting, the battery bus has about 12V, while the VR
provides a route to ground, so the light will light until the alternator
starts generating current. Once you are running, both the VR and the
battery bus should have the same potential relative to ground, ie about
14V, so no light should show. With the modern alternator, the light will be
out whenever the engine is running unless your wiring is screwed up: look
for an intermittent short, corroded connection, or bad crimp.

Mike Frank

At 01:10 PM 7/26/2004, you wrote:

I drove the car into town for dinner with my wife* and since the speedo is
removed (being fixed at Nisonger as we speak) I noted an intermittent
glowing around my knees. Upon further investigation it turned out the
ignition idiot light was just barely coming on, at intervals… like a kid
playing with a rheostat. (we all did that as kids, right? see how low we
could go before the light went out.)

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

9

Chuck,

Unless I’m mistaken (probably), the ignition warning lamp on your
car actually operates from an oil pressure switch in the block.

I’m not familiar with l.h.d. cars, or when the various changes to
the electrical systems were made, but certainly on my 64 4.2 rhd
car, the ignition warning lamp has absolutely no connection with
the electrical charging system on the car.

Did it only come on at low engine speeds?

I did not really notice all the conditions, as I said, it was quite
faint, and I only caught it as we pulled up to our house. The engine
was running slow at the time though.

I’ll wait until dark tonight and give it another try to see if I can
see the situations where it happens.

I DID notice last week, when I was removing the speedo, and
labelling the wires/lights so I could put everything back together
correctly, that the ignition light wires is the same color code
(beige w/purple dashes) as one of the two wires that come out of my
Alternator. This wire: (on the right)
http://www.goolsbee.org/rttg/myalt.jpg

I’m not saying I know this is the same wire, just that it is the
same colors. =)–
–chuck goolsbee
65ots, 1E10715
arlington, wa, usa

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

10

In reply to a message from chuck goolsbee sent Mon 26 Jul 2004:

Chuck,

You need to find out whether your car is fitted with a 3AW unit (or
equivalent) ,or an oil pressure switch.

Have a look on the engine block, just in front of the oil filter
aluminium housing. If there is a conical screw-in switch with a
wire coming out of it, chances are its a switch that operates from
engine oil pressure that lights your ignition warning lamp.

I believe that the 3AW unit was only fitted to the later 4.2 cars,
so unless yours is a modification, it shouldn’t have a 3AW unit at
all.

Regards,

Garth.–
Dr.G
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

11

Garth,
That is true of some cars but I suspect not Chuck’s. AFAIK all of the S1 cars equipped with an alternator have a silly circuit driven by a special take off on the alternator then passed through a “3AW” kinda switchy thing which drives the light. Its possible that the special output from the alternator could be toast and the car would still charge fine. Mike Frank has a replacement device for the 3AW which works but is dubious at best.
pauls 67ots

In reply to a message from chuck goolsbee sent Mon 26 Jul 2004:

Chuck,

Unless I’m mistaken (probably), the ignition warning lamp on your
car actually operates from an oil pressure switch in the block.

I’m not familiar with l.h.d. cars, or when the various changes to
the electrical systems were made, but certainly on my 64 4.2 rhd
car, the ignition warning lamp has absolutely no connection with
the electrical charging system on the car.

Did it only come on at low engine speeds?

Regards,

Garth.
<<<<<<<<<<

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomoFrom: “Dr.G” dr_nicholson@yahoo.com
Subject: Re: [E-Type] Ignition Idiot light?

12

Oooo that’s interesting, news to me. Do all of you with a '66 use the
pressure sw.?
pauls 67ots

On my 66 it is controlled by an oil pressure switch.

tom
<<<<<<<<<<

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomoFrom: “tom felts” tomfelts@earthlink.net
Subject: RE: [E-Type] Ignition Idiot light?

13

In reply to a message from Paul Spurlock sent Mon 26 Jul 2004:

Paul,

As I said, my S1 '64 4.2 has a pressure switch, and all 4.2 cars
were originally fitted with alternators as far as I’m aware.

So just to reiterate, the 3AW unit was not fitted to the earlier s1
4.2 cars, but I’m unsure as to when the change was made. If Tom has
a '66 with a pressure switch, then Chucks car should probably have
a pressure switch, unless it’s a modification (or Tom’s car is
modified for that matter).

Regards,

Garth.–
The original message included these comments:

Garth,
That is true of some cars but I suspect not Chuck’s. AFAIK all of the S1 cars equipped with an alternator have a silly circuit driven by a special take off on the alternator then passed through a ‘‘3AW’’ kinda switchy thing which drives the light. Its possible that the special output from the alternator could be toast and the car would still charge fine. Mike Frank has a replacement device for the 3AW which works but is dubious at best.

–
Dr.G
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

14

Chuck,
I don’t know what that is but I do know why your demister doesn’t work
:slight_smile: Wild guess someone has put in a relay to run something… a
cooling fan. Higher wattage headlamps??? If you have the 3AW its
mounted horizontally right under the heater box. A silver cylinder.
pauls 67ots

There is a relay (4AW) that controls that light,
Do you mean 3AW?

Sounds like it is bad.

Ray L wrote me offlist and said the faint glow was “normal” but a bright one is cause for concern.

If
so, do yourself a favor and replace it with a solid state equivalent that is
available from CoolCat (www.coolcatcorp.com)

Actually, I think that is already the case. I never could find a 3AW relay in my car as it was described in the manuals and by others here on the list. But there is an odd extra bit of hardware inside my dash:

http://chuck.forest.net/jag/saturdaydrive/SaturdayDrive-Pages/Image17.html

<<<<<<<<<<<

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomoFrom: chuck goolsbee cg@goolsbee.org
Subject: RE: [E-Type] Ignition Idiot light?

15

Paul------I’m repeating myself, but my S1, with alternator, uses the oil
pressure switch—it does not have a 3AW.

tom

[Original Message]
From: Paul Spurlock jagdood@earthlink.net
To: jaguar e-type@jag-lovers.org
Date: 7/26/04 9:59:40 PM
Subject: [E-Type] Ignition Idiot light?

Garth,
That is true of some cars but I suspect not Chuck’s. AFAIK all of the S1
cars equipped with an alternator have a silly circuit driven by a special
take off on the alternator then passed through a “3AW” kinda switchy thing
which drives the light. Its possible that the special output from the
alternator could be toast and the car would still charge fine. Mike Frank
has a replacement device for the 3AW which works but is dubious at best.
pauls 67ots

From: “Dr.G” dr_nicholson@yahoo.com
Subject: Re: [E-Type] Ignition Idiot light?

In reply to a message from chuck goolsbee sent Mon 26 Jul 2004:

Chuck,

Unless I’m mistaken (probably), the ignition warning lamp on your
car actually operates from an oil pressure switch in the block.

I’m not familiar with l.h.d. cars, or when the various changes to
the electrical systems were made, but certainly on my 64 4.2 rhd
car, the ignition warning lamp has absolutely no connection with
the electrical charging system on the car.

Did it only come on at low engine speeds?

Regards,

Garth.
<<<<<<<<<<

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

16

Chuck,
I don’t know what that is but I do know why your demister doesn’t work :slight_smile:

yeah, me too. =)

I try not to drive if it will be required.

Wild guess someone has put in a relay to run something… a cooling fan.

That is likely.

Higher wattage headlamps???

That is NOT likely, as I can drive around with my “high” beams on
with nary a blink from other drivers. Of course, all the other
drivers in my area are in jacked up pickups and SUV’s so it would
take a near-vertical beam to cause them any trouble! =)

If you have the 3AW its mounted horizontally right under the heater
box. A silver cylinder.

No such animal.
http://www.goolsbee.org/rttg/voltagereg.jpg–
–chuck goolsbee
65ots, 1E10715
arlington, wa, usa

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

17

So just to reiterate, the 3AW unit was not fitted to the earlier s1
4.2 cars, but I’m unsure as to when the change was made. If Tom has
a '66 with a pressure switch, then Chucks car should probably have
a pressure switch, unless it’s a modification (or Tom’s car is
modified for that matter).

So does that mean my “ignition” light is really a “low oil pressure”
light then?–
–chuck goolsbee
65ots, 1E10715
arlington, wa, usa

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

18 
    The only purpose of the light is to warn you that the key is

in the “on” position, but the engine isn’t running.

I’ve never noted that condition.

    Catch me up. When last you reported, you had a Lucas, but

you were going to switch to a GMtachidenso or something like that.

Still running the Lucas. I have a Hitachi on my workbench, but I’m
still working on making a fan fit it properly. The project has been
on the “back burner” for a while.

Otherwise, the intermittent light could be due to any
number of conditions, such as carbonized slip rings, a bad voltage
regulator (never happens, right?), or a bad relay. On older cars,
the light is triggered by an oil pressure switch rather than a 3AW
relay, and the sender could be bad.

I could grasp that “bad sender” concept, as my oil pressure gauge has
always given odd readings. I’ve grown to ignore it mostly, as I
assume it outright lies all the time. I figure if it drops to “zero”
I should worry, otherwise, I ignore it.

I assume the fix for this is a new oil pressure sender? I’ve priced
those at the “usuals” and have placed it on the “someday” or
“post-lottery win” category. =)

    If you've switched to a modern alternator,

Not yet, but I’ll keep your information for when I do.

Thanks,–
–chuck goolsbee
65ots, 1E10715
arlington, wa, usa

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

19

Chuck,

You need to find out whether your car is fitted with a 3AW unit (or
equivalent) ,or an oil pressure switch.

Have a look on the engine block, just in front of the oil filter
aluminium housing. If there is a conical screw-in switch with a
wire coming out of it, chances are its a switch that operates from
engine oil pressure that lights your ignition warning lamp.

I’ll check tonight.

I believe that the 3AW unit was only fitted to the later 4.2 cars,
so unless yours is a modification, it shouldn’t have a 3AW unit at
all.

Regards,

Garth.

I suspect you are correct, as I have never seen a 3AW anywhere on my car. (yet)

thanks,–
–chuck goolsbee
65ots, 1E10715
arlington, wa, usa

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

20

At 05:59 PM 7/26/2004, you wrote:

Garth,
That is true of some cars but I suspect not Chuck’s. AFAIK all of the S1
cars equipped with an alternator have a silly circuit driven by a special
take off on the alternator then passed through a “3AW” kinda switchy thing
which drives the light.

I’m not sure where the cutoff is. For sure, all S1.5 & S2 cars have the 3AW
relay. But It’s possible that most S1 4.2 cars had the pressure switch.

Its possible that the special output from the alternator could be toast
and the car would still charge fine.

No, this isn’t possible. It’s possible that the wiring between the
alternator and 3AW relay is bad, or the relay is bad. But the “special
output” is just a tap to one phase of the stator. If this output isn’t
around 7-9V AC, then the alternator is fried.

Mike Frank has a replacement device for the 3AW which works but is dubious
at best.

?Dubious? I don’t know of any failures of my device, which is more than
Lucas can say…

Mike Frank

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo