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Dead Battery Mystery

About a year ago the side signal lights were stolen (read:ripped) out of the side of my car. When I found my car in this state, I also found the battery dead. Replaced the battery had the dealership fix the lights.

After that, if I did not drive the car for say about a week, I would come back to find the battery dead again. I took it back to the dealership, but they couldn’t find anything wrong.

Time goes by and the problem gets worse. Now, if I don’t drive the car about every other day, the battery is dead. I took it back to the dealership and they hooked it up to some machine over night and told me that according to that machine, there was no changes to the battery over a 16 hour period. I told them to keep the car for the weekend (knowing that to be the kiss of death for said battery). On Monday morning they called to tell me the car started just fine.

I take the car home, drive it all week, park it on Friday and Sunday morning it is dead again.

Now 1 year, 3 batteries, and 4 trips to the mechanics and I still have the same problem. Any ideas?

Year, make, and model please?

Assuming you didn’t have this problem before the lights were stolen, I’d suspect a problem in the wiring to the lights in question.

I suggest you have someone test the charging system. Parts stores often do this free.

If we run with the clue that it did not die when the dealer left it over the weekend, but it reliably dies when you leave it over the weekend, then we would look for something that you do differently from the dealer - like a radio left on with an amplifier that is not turning off when the key is off, or a charger of some sort that is left plugged in to a live lighter outlet while the car is off.

I don’t think this is going to get fixed until you buy a voltmeter, put it between the battery cable and the post, and start unplugging fuses until the drain goes away. Start with the voltmeter. If you show full 12.6 volts between the battery and the cable, the drain should be easy to find. If the drain is slow, you may need to use the ammeter function of the meter. The ammeter is a better tool for the job, but many meters don’t carry enough current to handle a significant battery drain.

It is a 2002 Audi A4

Sorry, for leaving that out.

There is a new car radio (just the face plate/radio, no additional speakers) and an after factory alarm system (installed by the dealer). There are no devices left plugged into the car when parked (risk of theft).

I will look into the voltmeter idea, seems worth a shot, thanks!

When you start testing circuits, check the one for the aftermarket alarm. Perhaps the dealer keeps the car inside and doesn’t set the alarm. The alarm must draw current in order to work, so that could be your problem.

Thought of that idea with the alarm. Drove the car around to charge up the battery then left it parked two nights unlocked. The battery drained just as it always has. I think the next path is to check the radio circuit.

This article should help you use that electrical multimeter:


thanks! That helps a lot, I have to admit, I was a little lost before.