I did do some searching previous to posting here and just didn't have much luck finding a similar post, so here goes...

I have an 01 A6 2.7T Q with around 130k. Just last week with a 2 month old battery after leaving the car undriven for a long weekend, I came home to find the battery completely dead. No accessories or lights were left on. I jumped the battery and it started easily. Oddly, it immediately gave me a battery warning light (first time I've ever seen that warning and I've ran previous batteries dead MANY times... No dinger to reminder me to turn off lights). Then I noticed that oddly, the volts was pegging HIGH at 16+. This happened for a minute or two and then the car "settled down" and the volts leveled off at 12 and all was good. I also noticed that curing the time the volts were pegging, numerous accessories were not avaialble (sunroof didn't work, dash lights and dash info screen went out, radio was off, etc.). In speaking with an Audi Mechanic friend breifly, he said to check the battery, which I did at the local O'Reilly and then said the battery is perfect. He also said to put a multimeter on the batter (vehicle off) and then start pulling fuses one by one to see if I could see a jump in voltage at any fuse point - apparently this would tell me if a particular component was draining excessively. Not dice... pulled all the fuses one by one and the multimeter never budged.

So. Thoughts? This appears to have been am abrupt onslaught. The O'Reilly guy actually said that his "tool" said the alternator was in perfect working order too. Not sure how much to trust that, but I do trust those guys as much as any parts store guys. I spend a lot of time/money wit them and I believe they are shooting me straight.

Any ideas on what could be happening or at least what I should check next? I JUST checked the car after 2 hours after running and it started right up, however I suspect it will be dead by morning.

Thanks in advance, JR

 

UPDATE: the car was surprising not completely dead this morning. Actually started, but there was a noticeable tug to get it to turnover. And once it did, same thing... the volts shot up to 16+ (though I didn't get the battery warning light)... then abruptly settled back down to around 9-9.5ish (lower than usual) and the sunroof was disabled until the volts came back up to around 10-11.

Oh and before bed last night I took a voltage reading on the battery with the car off and it registered 12.34V... this morning 11.15V. Not a HUGE dip, but a dip nonetheless.

No idea what is going on, but something is draining the battery. Any further ideas on how to track this down? I love wild-needle-in-a-haystack-goose-chases!

 

Charge the battery disconnected from the car for 24 hours. Load test the battery. If it tests good, check the alternator. If it checks good, start with an ammeter and measure current drain. Pull fuses to slate draining circuit. Fix as necessary.

 

So O'Reilly said they charged the battery fully last night - took about an hour on their "supercharger". And they said it was rating actually about the cold cranking amps for that battery (908A versus the rated 900A).

When we reinstalled it, they tested it on the car and said everything checked out "perfectly". And not just okay, but at/higher than spec.

They said the electronic tool that used could determine alternator strength/health as well and that it checked out fine. Which makes sense... the car runs forever once it's on... it's only when the car is left OFF for an extended period of time (24hrs+) that it goes dead, which to me... eliminates the alternator theory.

And as I said in my OP, I had a multimeter on the battery yesterday and pulled every fuse to see if there was any evident drain "jumps". There were none.

Next?

 

maybe before you rudely dismiss a respected members advice/methodology, you should try it out ?

if not, continue to believe the O'rilley guess-o-meter and see if they can help you further.

 

Bad alternator.

 

Put your multimeter on ammeter. Use a 10amp scale or highest to start. Hook it up in series with the positive terminal of the battery and the battery cable terminal. Successively change ammeter scale to the point where you get a good deflection or milliamps...idea is to actually get a current drain reading rather than 'jumps' or whatever that means. If you have a fluke or similar meter that records max leave it on overnight. Don't open doors, sit on your key fob, etc.

Repost when you get a reading. That's the drain. If you have no reading overnight yet your battery is dead, you have a bad battery that won't hold a charge.

 

Meh. I didn't take it as rude. I've probably been a lot worse. Took my xanax this am too...

 

oooh, yes, but OReilly said it was ok.....LOL.

 

Awesome... Will do (hoping that I understood all that... which I think I did.) Thank you so much.

LOL - Oh give me a break... not all parts store guys are idiots. And I did say that I'm not sure how much to trust them.

Wow, someone gets their panties in a bunch in hurry around here! So "rudely dismissed a respected member"... REALLY? First of all, I apologize to HIM if I did in fact so rudely dismiss him (which I don't believe I did). I was simply going through the quick bits he briefly described, thinking - granted, in my limited knowledge - that I had already done those items. And btw, as I said before, I DID try most of the items he mentioned. Seriously, lighten the F up.

As I mentioned above - DISCLAIMER: not meaning to RUDELY DISMISS YOUR ADVICE/METHODOLOGY - if the car runs just fine when the alternator is engaged (car on) and charges the battery just fine then, but the battery only goes dead when left set for extended periods of time (24 hrs +), wouldn't that have nothing to do with the alternator, if not actually confirming the alternator is NOT the issue? Seriously, just asking so I can better understand all this.