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AudiDoc
AudiDoc, Independent Audi Shop Owner
Category: Audi
Satisfied Customers: 1695
Experience:  I've been working on Audis since I was 18 and own an independent Audi repair and performance shop
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Audi S4: OK, so some more info . The battery is fine.

Customer Question

OK, so some more info for you. The battery is fine. The battery/alternator/starter harness links into the main engine harness. Here is where the mystery begins. When the car is on - the alternator does not run. If we unplug the battery harness from the engine harness and we run a hot wire directly from the battery in order to power on/charge the voltage regulator - the alternator runs fine. So, when plugged into the main harness the alternator is not getting a signal as to when to turn on. If we force the signal - it works fine. It seems to me like an ecu problem?
Submitted: 7 months ago.
Category: Audi
Expert:  EricFromCT replied 7 months ago.
Hi. Did you compare the wires in the connectors of the old harness to the wires in the connector of the new harness? To see if the pins are in the correct position at least. To start with.

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