charging system problem

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njot - 22 May 2007 21:45 GMT

I have a 78 Trans Am which has had a recurring issue with the charging
system.
I'll start the car and drive off, and find that the alternator is not
charging. Voltage gauge at ~12 volts, turn signals slower than usual,
lights dimemr then usual, etc. Then suddenly, the gauge will read
13.5 volts and everything is OK.

I had this issue in the past, and over time, the amount of time before
the alt started charging would take longer and longer, until finally
the alt no longer worked and I had to replace it. This after making
sure the belt was tight and the battery was OK.

The new alt started out OK, but eventually, it too started this same
strange pattern again over a few thousand miles or so until it too
stopped working.

I thought it was just a poorly made remanufactured alt, so now I am on
the third alternator. It has been fine for a year. Now I just
noticed the other day that it started off at 12 volts again for about
10 minutes of driving, then suddenly went up to 13.5 volts.

I don't know what is wrong or what to look for. The problem must be
originating from somewhere other than the alternator, but it
ultimately becomes affected. The belt is tight enough, the battery is
fairly new.

Has anyone else had a problem like this, and if so, what caused it?

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Tom S - 23 May 2007 00:13 GMT

>I have a 78 Trans Am which has had a recurring issue with the charging
>system.
[quoted text clipped - 23 lines]
>
>Has anyone else had a problem like this, and if so, what caused it?

I think they were still using voltage regulators (instead of a relay
block) in 78. You could have a weak voltage regulator.

Tom S.

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njot - 23 May 2007 14:31 GMT

> >Has anyone else had a problem like this, and if so, what caused it?
>
> I think they were still using voltage regulators (instead of a relay
> block) in 78. You could have a weak voltage regulator.

I would agree with you, except that the voltage regulator is inside
the alternator, so each time I put on a new alternator, I put on a new
voltage regulator, too.

I also checked the wiring to and from the alternator and as far as I
can tell, it's OK.

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yocj - 24 May 2007 22:49 GMT

My 85 had a similiar prob = and it was the alternator.
But
to test it and have it fail it had to be IN the car and tested IN the
car,
when pulled out of the car it passed with flying colors yet it was
still leaving me stuck occasionally
but not regularly

change both voltage regulator and alternator.

Check out Jones racing products - they have refurb'd alternators for a
good price.
-CJ

> I have a 78 Trans Am which has had a recurring issue with the charging
> system.
[quoted text clipped - 23 lines]
>
> Has anyone else had a problem like this, and if so, what caused it?

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