86 TC Won't Charge

January 22, 2010, 10:03:19 PM

Hey there everyone, long time, no talk...got a problem.

For some reason, my charging system isn't working well. I just had a rebuilt engine installed and noticed the alternator wasn't charging. I replaced the alternator and it appeared to be putting out a little over 14 volts. About three days later my battery is dead. I put a voltmeter on the battery and I'm reading 11.5 volts. I take the alternator back to the store for testing and it tests good. Still, I swap it out.

New alt on, start car, got about 13.1 volts at the battery. The car runs okay, but it will have a dead battery with absolutely no warning. So, tonight, I put the voltmeter on the positive terminal of the alt and get 12.8 volts...at the battery, 12.7. I turn on the lighs and it goes down to about 11.8, radio, 11.6. I decide to let it run for a while...the voltage steadily drops. I let it get down to 10.5 volts before I turn the accessories off.

So, my first thought is the voltage regulator, but if it was the voltage regulator, wouldn't there be around 14 volts at the back of the alternator?

Thanks in advance for the advice.

86 TC Won't Charge

Reply #1 – January 23, 2010, 06:36:00 AM

Definately, there must be more than 13,5 (14,1 is ok). Did you control the diode block?

86 TC Won't Charge

Reply #2 – January 23, 2010, 08:29:44 AM

I had them test the diodes at the auto parts store. They were good.

86 TC Won't Charge

Reply #3 – January 23, 2010, 12:53:43 PM

I took a stab and swapped out the VR...that was it! Almost 14 volts at the battery...:D

Thanks all!