livetoaudi

2005 Audi A4

The other day I parked my A4 on my driveway overnight. It was raining all night.

Early morning I come out of the house and my brake lights are on. Both sides on - bright red-

The car was locked and everything off.

What in the world. The battery was not drained

Has that ever happened to anyone before?

Merkin

could be stuck brake light switch

diagnosticator1

Also, check for water leaking from the box to body seal, under the driver's dash, allowing water to soak the Central Electric Control Module. The CECM controls the exterior lighting, and is known to short out when wet. If the ECU box has water accumlation, it will overflow and drain down on top of the CECM.
Or, it could be what "Merkin" suggested, but if the brake lights where OFF, then ON later, and it was raining hard all night, then water ingress is consistant with that symptom. It's also possible for the plenum water drain to be plugged with leaves and other trash, causing water to accumulate in the plenum and leak into the car and soak the CECM. The plenum drain is under the battery, you may need to remove the battery to clear the drain.

Pabblo

Happened to me. Brake light switch replaced.

livetoaudi

Update

It happened again last night.

This time in my garage. It has not rained in a few days, so probably not water related. I have to really check for moisture in the plenum.

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One detail I did not mention before.

The first time it happened was two days after taking my A4 to the dealer for a "computer update" recall. My A4 is still under warranty so I will ask them about this issue. Did the update change something to do with the lights or did they not seal the cover properly and moisture got in?

Problem is, the closest Audi dealer is about 100 miles away each way.

Don't mind the drive. Only time off from work.

6300_RPM

Brake ligth switch is out, you can get an OEM one online cheap, intallation is easy and not worth labor charges at a dealer

livetoaudi

OK, I agree it must be the switch.

The weird thing is that is only happening at night when the car is just sitting there.

At the moment it is happening I go and step on the brake pedal a few times and the lights stay on. Then I turn the ignition and everything goes back to normal.

I can change the switch myself but I have to go back to the dealer next week anyway for a new remote & key. I will have them do it since it is still under warranty.

Thank you all for your comments and help.