Ok, so last November my stock alternator packed it in, so I replaced with an Autozone one. It died quickly, so I got another one. Then today I replaced it with a GM reman alternator. Unfortunately, I've had a common problem with all 3 of my replacement alternators.



With the headlights off, everything is just peachy. When I turn the headlights on at idle, the battery voltage takes a dump down to about 8v from the usual ~13.5v. If i raise the RPMs to ~550-600, the battery charges again and it's happy. This is not normal behaviour, the bloody thing should keep a relatively constant voltage even when the headlights come on. So, i have some questions to help the discussion:

1) Are my headlights possibly drawing too much current and dropping the battery voltage? I guess I need to get out there with a multimeter, but I would appreciate the schematic if anyone has it.

2) Do most A4s idle at ~480rpm once they are warmed up? If my idle somehow dropped, that could be fun.

3) Is there a mechanism for the headlights like on the AC where the AC will draw more current when starting up? If that is out of wack, then it could be drawing too much current or drawing for too long.

I'm kind of at my wits end right now. This is the third time I've changed the alternator, and it never gets any fkn easier, I can tell you that much. Especially when the alternator bracket is hot.

Anyway, thanks for your help... I'm about to take it to the shop next week if i can't get this pinned down.

 

you might actually want to check the wires and see if there carrying the proper load

 

Yeah I'm going to take an inductive ammetre home from work today to check things out hopefully. Could have a leak somewhere.

 

ok, so the AC does this too when it comes on




Where is the voltage regulator in our cars?

 

Internal within the alternator.


You could take out the alternator and bring it down to your autoparts store so they can "bench" test it. If it comes up good you probably have a problem in your connections.

 

Your idle is too low, IMO. Has it always been so low?

 

I'm thinking underpulley kit if there is nothing wrong with the wiring leading to the headlights...

 

It's possible the pcm could not be controlling it properly. But I'd start with checking all of the power and ground connections and maybe replace the one wire weather pack connector for the regulator. If your battery is low you are already at a disadvantage. It needs to be fully charged the alternator is not designed to charge a dead or extremely low battery. Or as mentioned earlier you may have an UD pulley if you just bought the car.

 

nah, i've had the car for years and this started last November when the original alternator died.

 

usually for me, if an alternator goes, the battery isn't too far off from going as well. a battery that doesn't hold a charge well, or was discharged significantly forcing the alternator to recharge was enough to kill 2 of them in one of my cars before I changed out both alternator and battery at the same time. Worked great after that.

 

So yesterday the dealership told me that my battery had low CCA (450 instead of 650), so I said, "I really don't think that is the problem."

I took the battery out and went to Autozone and had them load test it for me and the battery passed 3 times. The shop is claiming that my car is behaving normally for a Trans Am. So just so you know, your car should fully discharge the battery after having the lights on for 5 minutes. Fkn bullsh1t.

Guess I'm just going to have to pay te $45 diagnostic fee (what exactly did they diagnose?) and work out the problem myself.