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Chris (aka - Moose)
Chris (aka - Moose), Technician
Category: Audi
Satisfied Customers: 48725
Experience:  16 years of experience
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I have a 1996 audi a4 quattro 2.8l with a battery light on

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I have a 1996 audi a4 quattro 2.8l with a battery light on (sort of dim, but on). I checked the voltage at the battery while running and it's about 11.8 volts (12.2 with the engine off). I removed the alternator and had it tested, and it came back functioning normally. I then reinstalled and got the same results (not charging). I tested for continuity between the "B" wire (sorry if my nomenclature is not correct, but the small wire that controls the output of the alternator through the voltage regulator). With the key on, there should be continuity between the positive terminal and the wire (I think). I was able to establish that there is a connection between the terminal on the wire up to the box where the ECM is houses (on the firewall, drivers side.) But I don't know where the wire goes once it enters the cabin of the car, or if there is a fuse between the ignition switch and the alternator somewhere. I really need wiring diagram of the internal fuse and relay distribution box under the dash.
JA: Have you tested the battery? Have you tried testing the alternator?
Customer: Both test good. The alternator was out of the car when it was tested.
JA: Are you fixing your A4 quattro yourself? What have you tried so far?
Customer: I removed, tested, and reinstalled the alternator with clean electrical connections. I tested for electrical continuity between the small "b" wire and the positive battery terminal, and there was not a connection (with the keyswitch on). I then tested all the connections I could find between the alternator and the key switch. There is a connection on the passenger side of the firewall (harness to the starter and the alternator), and from that connection to the connectors in the plastic box where the ECM is located. All checked out fine. I think there should be a fuse between the key switch and the alternator, but I can't find any information on that.
JA: Anything else you want the mechanic to know before I connect you?
Customer: No, I think that's all.

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While running what is the voltage on each wire color at the alternator?

Customer: replied 1 month ago.
The battery was dead, so when I get a charge on it, I'll let you know.

Thanks

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