charging circuit diagnostics

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Feb 10, 2013 | 05:18 PM

Solid20vq

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Joined: Feb 2012

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From: Ashland Oregon

charging circuit diagnostics

When I jump the car, the aux gauge voltmeter reads 12.6-13v steady. As soon as cables are removed, gauge reads 12v or less; volts increase minimally with rpm, but doesn't maintain voltage as loads are added. Multimeter reads 12.3ish on the battery, while car is running, and a variable 11.9-12.8ish volts on the alternator, with load or without.

I'm guessing its the alternator, what do you think?

Feb 10, 2013 | 05:54 PM

socalclimber

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Joined: Feb 2007

Posts: 262

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From: Claremont, CA

check alternator exciter circuit and ALT dash light

Quote:

Originally Posted by Solid20vq

I'm guessing it's the alternator, what do you think?

Alternator indicator light in dash MUST illuminate with ignition in ON position, and go out once engine is started. Does it?

If indicator light does come on with ignition ON, and goes out with engine running, yes, I would say alternator is bad.

Alternator will not charge if this exciter circuit has a problem or indicator light is burned out.

I can scan diagnostic page from Bentley, if you need these details.

Feb 11, 2013 | 07:46 PM

x19

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Probably, brushes on Voltage Regulator worn out or may need to replace the alternator,

Feb 12, 2013 | 12:45 AM

Solid20vq

Thread Starter

AudiWorld Member

Joined: Feb 2012

Posts: 125

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From: Ashland Oregon

Quote:

Originally Posted by x19

Probably, brushes on Voltage Regulator worn out or may need to replace the alternator,

So I replaced the alternator, yet the same symptoms persisted. Multimeter was reading out at least 13v output on the alternator. Aux gauge inside was only reading about 12v though. Eventually the car died, and emitted an electrical-smelling cloud of smoke from the front of the engine. I had perfect continuity between the alternator and the battery though... guess its time to rip apart the harness?