Another Electrical Puzzle

Here's one for the experts...
2001 Audi A6, 50000 miles.
This has been a fairly trouble free car except for front end woes fixed under warranty and one electrical gremlin that occasionally blows fuses
to the rear power outlet (lighter).
Anyway, my wife drove it all day in the rain today, starting and stopping at various places with no apparent troubles. Tonight, she stopped for 20 minutes, and when she came back to it to start it, all she got was clicking. She tells me the interior lights were fairly dim. OK...so after she panicked a bit on the phone, she called back and said that the interior lights got bright and the car started. The only remaining symptom was that the radio is in "safe mode" as though the battery had been disconnected.
So....it sounds like a dying battery that couldn't turn over the starter....except why would there be low juice at first and then enough to start it 10 minutes later? It wouldn't be a loose connection, because there should have been no power at all. I'd suspect the alternator, but then the battery should have just died and stayed dead. Could it be the starter itself -- can the starter gears "jam"? (for lack of a better term) Moisture somewhere? Or just the usual 2001 A6 electrical gremlins?
You can certainly see that figuring this out could run into serious money as the mechanic spends hours and hours looking for something that is no longer there -- until the next time, that is.
Maybe time for new battery, at least?
--
Wayne Crannell
Xxxxxxx, TX
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How old is the battery? If it's original, I'd consider replacing it and see if the gremlin is gone for good.
Otherwise, if we presume the battery is ok....if the alternator belt was slipping in the wet - or the alternator is simply on its way to Heaven - and your SO had a healthy electrical load on the battery (headlights, heater or AC, etc) it's conceivable she flattened the battery. Removing the load would allow the battery to build up a surface charge which would give the appearance of health - for a very short time, anyway, enough to brighten the lights and perhaps to start the engine up.
Doubtful all those problems were caused by a fritzed starter motor (and I've never heard of one locking up - the typical failure modes for starters are open windings and shot bendix gear).
I'd still vote for the battery if it's original. My original battery lasted for four years less three months, and afaik it was a four year battery (it might have lasted longer had it not been flattened by a rear passenger reading lamp inadvertantly left on for a couple of days :-(
/daytripper '00 s4 6spd
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Trim

Trim
I've known pre-engaged starters not fire once in due to a faulty winding - solved by hitting it with a hammer! And the old bendix type not unscrewing themselves once started and burning out the starter motor.
Other than that I would agree it sounds more like a battery problem.
I've got a 2002 A6, which had its alternator changed when one of the warning lights came on (Traction control I think) - and then again about a day later with the same problem. Other than that I've had no other electrical problems in 55,000miles. Hopefully my new one will also be as trouble free.
Mark
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I doubt that the battery would bring itself back to life in so marked a fashion. A failure of a pre-engaged starter motor would not reduce volts and put the radio into 'safe' mode. I think that it's much more likely that there's a bad or loose connection between the battery and the rest of the car (either chassis or live wire).
--
Peter Bell (Note Spamtrap - To reply, replace 'invalid' with 'bellfamily')

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I second trip's nomination. Take out the battery and have it load tested at an auto parts store. It could have a bad cell that can make the appearance of an intermittent failure.
Same thing happened on my wife's Lexus with a less than two year old battery.
Dimmed lights indicate low voltage, not a starter problem.
If it's old, even if it tests good, replace it anyway.
Same symptoms can be caused by corroded battery connections. Clean with baking soda and a wire brush when you replace the battery.
Good luck!
--
Stephen Clark
89 Audi 100
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18 months old. Shows no problems after I messed around today. Drove the car with absolutely no issues today.
I guess we'll have to get stranded to find out what's wrong!
--
Wayne Crannell
Xxxxxxx, TX
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Ah - 18 months old? In that case I'd be looking for a poor battery connection, either the big fat cables at the battery terminals, or a grounding cable working its way loose. Driving in the wet could aggravate a poor connection and provide similar symptoms to what your SO experienced...
/daytripper '00 s4 6spd
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Wayne, Look for a faulty or dying Fuse. They do age and wear out with use. Michelle
Wayne Crannell wrote:

--

Michelle P ATP-ASEL, CP-AMEL, and AMT-A&P

"Elisabeth" a Maule M-7-235B (no two are alike)
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---Snip---
Fuses do not age and wear out with use. Rubber ages, brake pads wear out, but fuses last almost forever if not murdered. The problem is most likely a bad (intermittant - high resistance) connection in the power circuit.
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