[Saloon-lovers] Charging system

Neil wrote,

Looking at the dynamo I have (which I am told came from a 

Mk2 Jaguar) it does look bigger that the ones I have seen on other
Mk2’s with power steering. Whilst it will fit (just) does anyone
know how I can identify the model of dynamo? I have checked the
side and cannot find the usual stamping such as C45.

All help received appreciated and any other comment also appreciated

Hello Neil,

There was an optional C48 generator, I have one and it is physically much
larger and heavier than the C42 or C45. It is only rated at 35 amps but the
output at low speed is much better.

There are three adjustments for the regulator. The current output is
adjustable, but you need to follow the procedure in the manual and close the VR
contacts. You can make a tool from an old screw driver with a bench grinder. I
would clean up the VR contacts with fine paper and a solvent and try to adjust
it following the procedure in the manual. Make sure all of the wiring
connections are clean and tight. What is the voltage at the battery @ 1800 rpm ?

Paul

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Don wrote,

This is a weird one…
Starting the car from cold, the ammeter shows good charging initially, then
after about 5 minutes (on the road), suddenly stops charging as if it is
running at idle speed (the ignition warning light does not come on- as long
as the engine is running above idle)
After another 5 minutes or so, the dynamo seems to cut in again and I get a
good charge reading on the ammeter (as good as just after starting) and it
is OK until the next cold start.
I have tightened up the fanbelt which was loose as I thought it might be
slippng under load- it has had no effect.

Hello Don,

I don’t know what you mean by “good charge”. When you start the car, the
starter consumes a lot of power and the ammeter should show the recovery. After
that, the ammeter should stay in the middle. The ammeter can be a little
crazy, I would hook up a voltmeter to the battery and test the running voltage.
Voltage at rest should be 12.6 volts. If not, charge the battery, before
testing. Running voltage should be above 12.6, anytime the voltage is over 12.6,
you are charging, below 12.6 you are discharging. This is essentially what the
warning light is telling you, but a good voltmeter speaks more clearly. For
any starting/ charging problem, point your finger at the battery first, even if
it is new, you will save lots of time over the long run. My first step is to
swap a known good battery before even thinking about the problem.

Paul

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In reply to a message from Tlsalt@aol.com sent Tue 11 May 2004:

Hi Paul,
The voltage at 1800rpm is 12.60 volts. At idle the voltage is
12.50 volts. I tested a few times and it does consistently increase
by 0.10 volts each time.

I have also tried to adjust the current (with the VR contact
fixed closed). However I try I cannot get the output above 5amps.
Does this suggest anything to you?

Thanks for the information about the C48 dynamo being bigger and
heavier than the C45, C42. It does look like I have the C48 as the
one I fitted to try out and the C42 as the one that is on the car
originally (and back on it now).

Given I cannot get above 5 amps out of the current regulator I
think I need a new one. From what you say the C48 can deliver up to
35amps. The car has a RB340 box on it and I can see new ones for
sale with a rating of 11A up to 30A but nothing higher. Could this
be why its not working now after I have fitted the C48 for a trial?
What would you recommend for use with the C48?

Best wishes and thanks for your advice–
Neil. (Mk2 1967 2.4L O/D)
Warrington, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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Hi Paul,
The voltage at 1800rpm is 12.60 volts. At idle the voltage is
12.50 volts. I tested a few times and it does consistently increase
by 0.10 volts each time.

I have also tried to adjust the current (with the VR contact
fixed closed). However I try I cannot get the output above 5amps.
Does this suggest anything to you?

Thanks for the information about the C48 dynamo being bigger and
heavier than the C45, C42. It does look like I have the C48 as the
one I fitted to try out and the C42 as the one that is on the car
originally (and back on it now).

Given I cannot get above 5 amps out of the current regulator I
think I need a new one. From what you say the C48 can deliver up to
35amps. The car has a RB340 box on it and I can see new ones for
sale with a rating of 11A up to 30A but nothing higher. Could this
be why its not working now after I have fitted the C48 for a trial?
What would you recommend for use with the C48?

Best wishes and thanks for your advice

Hi Neil,

You are barely charging. It suggests a problem to me, but you already know
that. The voltage at VR terminal “D” @ 1800 rpm, with VR “B” terminal
disconnected, should be 14.5 to 15.5 volts depending on temperature. Did you do this
test? If the readings jump around, the contacts may be dirty.

There is no higher VR for the C48, you use the RB340 and adjust it. Do you
know the history of the Dynamo ? Have you met its parents ? Have you looked
through the window at the brushes? If a brush is worn out or stuck it should be
obvious.

Paul

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In reply to a message from Tlsalt@aol.com sent Tue 11 May 2004:

Hi Paul,
I did test the voltage and got a steady 14.8 volts. This was
the first test as per the book it was only the second test that it
failed.
To be honest I did not look at the bushes before testing. But
sertainly the one which was on the car (the C42) was working fine
before I put the C48 on it to test. Testing the C48 by the dynamo
test method in the manual (joining the two connections at the back
of the dynamo etc) it seems to work. I did not not try and adjust
the regulator when I could see there was no charge on the ammeter
and just put the C42 back on only to find it no longer worked
either. Bit of a stupid thing to do I know but what is done…

Given I cannot adjust I will try to get hold of a new RB340.

Thanks for yoru help.–
The original message included these comments:

that. The voltage at VR terminal ‘‘D’’ @ 1800 rpm, with VR ‘‘B’’ terminal
disconnected, should be 14.5 to 15.5 volts depending on temperature. Did you do this
test? If the readings jump around, the contacts may be dirty.


Neil. (Mk2 1967 2.4L O/D)
Warrington, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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Neil, I have a picture of C42 generator with PAS pump
on my web page http://kotisivu.mtv3.fi/jag/restor01.htm
(about middle of the page, scroll down) if you want to
check if your generator looks same. In mine, the number
was stamped in cover, but it may be covered with dirt/paint.

My charging problems were caused by broken brush spring.
Not that C42 is much better at low RPM even when OK…

Br, K�pi

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