Ok, I've got a '84 TransAm with stock engine setup. A few days ago at night (when I was running the headlights) I noticed while at a stop light my voltmeter - which runs usually around 13.5-14 volts - would drop down to 12-11 volts, with of course the instrument panel and headlights dim. Whenever I ran the engine up from idle the voltage would go back to 13.5. This wouldn't happen all the time but seemed to happen at random intervals whenever the engine was at idle.

My battery was pretty old so I replaced that- no dice. Thinking that it was the voltage regulator I changed out the alternator and while I think it worked, if I put a full load on the alternator (that is, turn on all the accessories) it'll drop back to 11-12 volts again (and yes it did this with the old alternator and battery)

Am I overlooking anything here? I checked my battery to ground resistance (at the engine) and it's only .2 ohms so I don't think it's a bad ground. Has anyone seen this before?

Would appreciate some suggestions- thanks in advance for the help!


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Original owner - '84 T/A w/stock 305HO 5-speed

 

it's not uncommon to have that happen. check for a loose belt. lot of places will test it for free.

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-=ICON MOTORSPORTS=-

 

Well I had Autozone test the alternator and the charging system. They said the old alternator was good, but the odd thing is they took a new one and put it on the bench and it tested bad. The counterman admitted that the testing system may need recalibration, so I don't know how good of a indicator that was....

When on the car and the test setup connected, the alternator was charging properly accoring to the tester- but that was without full load.

I'll check the belt tension again tho - the belt was replaced about a month ago for preventative reasons...


[This message has been edited by David Trimble (edited October 08, 2000).]

 

Well I'm still having the problem - it's intermittent, which is driving me nuts....

I put in a new battery- the one I have is 4 years old and with winter coming I figured I should change it out anyway. I even checked the ground resistance between frame and ground again and it was still good (> .2 ohms)

That didn't seem to help, and since Autozone wasn't able to figure out for sure if the alternator was bad I even went ahead and put in a new rebuilt unit. And I've double-checked the belt tension- I've got about a 1/2" deflection with medium pressure on the belt. I'm afraid if I go tighter I'll ruin the alternator bearings.

Has anyone ever seen this happen before with their car? I've had this car quite a while and up until now it's NEVER done this before.

Any help/suggestions would be greatly appreciated at this point!

 

Check both the positive & ground cables for tight connections & corossion. Also check the cables where they enter the terminal lugs for corrosion or a loose connection.