charging system problem

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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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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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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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

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