So I have a 87 s4 na, the alternator is a 110 amp alternator, after having it for sometime I had no issues with it, but then I have been having to rev the engine to charge the battery now right after start up. After that it will probably charge up to 13v or if my headlights and fogs are on it can charge between 13v till12v.

I don't want it to get lower than that cause if I forget to rev it after start up driving under load can be 12v or under and then if I shut it off then turn it on the battery dies.

So any advice will help, thanx in advance

 

what alternator is on it now,as the stock on is 65 amps?
are the belts tight?
did you wire the alternator up correctly to excite it IF it is a different alternator?

 

Chances are the alternator is failing. You could also check the two wire plug at the back of the alternator. W/key to on and unplugged the wires, B/W and W/B, should both have 12 volts.

 

Don't forget to charge and properly load test the battery. Sometimes its the simple things.

 

awww guilty! I wish the best for you. I'm PMing this thread to a buddy who is the expert on alternator issues and building himself, lulz