The voltage on my 1984 z28 with a 350 and a t5 drops when the car reaches operating temp. Itll be about 13-14 when I first start the car, and then it will drop to just over 12 and dips when the headlights are put on. The alternator is a rebuilt one. The last one had the same problem but worse. I thought it was the alternator ubt now im tihnking the grounds. Any ideas?

 

well if the issue only happens after the car reaches operating temp im assuming for some reason to much heat is hitting the alt and messing with it that way some how you could try heat shielding your exhaust and see if that helps

 

Im tihnking aobut that too. The car is running stock manifolds, and pipes though. Thats why I didnt think of that right away.

 

Is this problem causing any problems such as the engine missing?

 

No other problems really. I am looking to go to a dual fan setup becuase the car runs hot on the highway sometimes. The engine runs pretty well otherwise. The reason I'm thinking the grounds is that when you go to do something with the car off( put up the windows, leave the lgihts on for a sec.) the voltage drops a lot. If I remember correctly the voltage shouldn't drop that much, but maybe I'm wrong.

 

The problem occured again. The car was a bit low on coolant, but i know where the leak is. The voltage dropped to like 10 on the factory gauge when the lights were put on while I was on my way home. I just had my low beams on. The car didn'ty die, and would come back to like 13 when the lights were turned off. Could this just be the factory gauge, or the wiring to or from? I have no idea if the wiring on this car was touched, or how it would have been touched.

 

sounds like your voltage reglulator when it gets hot stops working or a bad ground somewhere heats up exspands and loses ground

 

Check your ground - Block to Firewall

Ive had this issue as well. Most likely a ground and that one is most common in my experince...

 

It could also mean the alternator is on it's way out. I had 2 different reman (duralast gold) ones die within a week. Both times, before they failed, the voltage would begin to slowly drop.

 

Check your block to firewall ground and the negative battery cable make sure its tight on the battery and were ever its grounded to. It probably just a bad ground and maybe the gauge, my factory gauge is always all over the place.