A6 / S6 (C5 Platform) Discussion Discussion forum for the C5 Audi A6 and S6 produced from 1998-2004

Odd alternator behavior

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Old Sep 12, 2007 | 07:50 PM
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Default Odd alternator behavior

'Tis the season for electrical oddity, apparently. I'd been having a progressively harder time starting the car for a week; battery seemed a bit weaker every time I started it, but then it'd run fine once started. I have a power amp and a little bit of other things plugged into the cigarette lighter in the back that slowly drain the battery; takes about a week to discharge it to where it won't start, but I've now read that those little trickle-discharge items are hard on the battery, so I replaced it. Seemed to work fine until today, when for some odd reason the whole car shut down twice while making somewhat hard right turns. On one of these occasions I noticed the voltage meter in the dash dip down toward 12 volts, and for the last week it's been sitting a little below 14, when my recollection is that it's usually a bit above. I'd suspect a short if it weren't for the fact that an intermittent cable doesn't explain the failure to charge the battery; I'd think if the cable was working 98% of the time until a hard right turn, the battery would stay charged. Thoughts, anyone? I'm pretty handy with a volt-meter...
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Old Sep 13, 2007 | 04:10 AM
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Default I think the drop in voltage is a product of the cut out, not the other way around.

Do you get any lights when the car cuts out? Does it come back on its own or do you have to restart it? Any codes?

Bad ignition switch?
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Old Sep 13, 2007 | 08:27 AM
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Default Re: I think the drop in voltage is a product of the cut out, not the other way around.

Haven't noticed whether I get any lights when it cuts out; next time I'll take notice. I have to re-start it, but it fires up immediately. No codes, and I think a bad ignition switch isn't impossible. Seems to be something that shorts out when I hang a right turn headed downhill for whatever reason. I'm going out with my meter now to do some tests...thanks for the response.
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Old Sep 13, 2007 | 09:00 AM
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Default Cable seems to be the right track.... but

not a short - an open. Possibly a high impedance ground (or hot, I guess). Corrosion, loose fitting, could all lead to this.

Grant
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Old Sep 13, 2007 | 10:03 AM
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Default Very probably a bad connection; where would I look?

Driving it around and watching the volt meter, it seems that it's braking, or generating any G's in a forward direction, breaks what's probably already a weak connection. Can anyone give me an idea what I might wiggle, or take off and clean, or check out to see if I can find this weak connection? FWIW, I'm not even sure what's the alternator on this engine...
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Old Sep 13, 2007 | 11:51 AM
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Default Ground strap. Alternator connections (both). Voltage regulator connections...

...to alternator (might be a plug). Might check tightness of everything, and you also might get contact cleaner, loosen majro connections, spray, re-tighten. The simple act of re-tightening causes connections to scrub and clean themselves.

Intermittent problems are devilish.

Grant
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