Hey all,

I'm currently stuck trying to repair my 2004 Audi A6 Quattro as it recovers from (what I believe was) water damage SOMEWHERE in the electronics system. Hold on to your chairs, it's about to get weird:

I come back to my apartment and see that my parking lights and rear lights are on; thinking somebody broke into my car, I run to the parking lot and find all doors are unlocked. However, no windows were broken and nothing was stolen. Extremely confused, I start my car up with no issue, let it run, and turn it off. However, my parking lights, side lights and tail lights STILL won't turn off even with the car/light switch off. Additionally, there is a one inch puddle of water in the seat behind the driver, and the driver's seat floor is soaked as well. My power locks and windows are also not working.

I pop the hood and notice some gnarly blue foam-like corrosion on the battery's negative terminal. The "trough" around the battery was also flooded with water, which is what made me infer that the electronics system had shorted out, resulting in the parking/side/tail lights permanently staying on. The weird part, to me, is that typically short circuits will trip a fuse, preventing devices from receiving power. However, in this case there is CONTINUOUS power being delivered to the lights, even if the key isn't in the ignition.

I read how A6 battery compartments can get water logged, so I did the whole remove the battery and clean out the drain (which was fully clogged) thing. Additionally I shop-vac'd the **** out of my driver and back seat. We also tried the whole ECU Reset technique by disconnecting the battery and touching both leads together. Then we recharged the battery only to see the same damn parking/side/tail lights come right back on.

SO. Any ideas on wtf is going on and how to fix this ?

Thanks in advance guys

-Matt

 

Hi.
Def sounds like it is down to the water ingress. There is an component called the Onboard Power Supply control unit, which controls the power supply to the lights, washers, wipers and other circuits. It is located up under the drivers side underdash trim panel. if the area behind the drivers seat was wet, then the leak probably came from the plenum area and contaminated the unit. Try visually checking and unplugging it to see if the lights will go out. if so, its probably got wet internally

 

Hi.
Sorry, ignore that as I thought you had an A4.