So I've got a 2001 A6 2.7T Quattro 6-speed manual with 151k on it, and when I turn the lights on the driver side brake light is on like it's braking but the passenger side is normal

The problem light was burnt out when I got the car so I went ahead and changed them both about 2 months ago.

This is the car just sitting with the lights on, this isn't normal is it? Anyone have any idea what's causing this?

 

It is the rear FOG light ON. (looks light the brake light is on for brighter lights in bad weather or foggy condition.
When you pull the head light switch, there are 2 clicks. The first click is for FRONT fog only, one more click both the front and rear fogs are ON. You push one click back the brake light on situation will go off.

 

It's not the rear fog light. I wish it was that simple and I was just dumb, but that's not the case. On this car the rear fog light is just to the left of the license plate, in the black area surrounding it.

Thanks for the response though.

 

Yes it's obviously not the fog light, it's not even the same location. So let's try to figure this out....

• Did it just start doing this? (could just be a bulb problem)

• Have you tried switching light bulbs? (obviously easy way to see if it's the bulb)

• Does it stay on regardless of you pressing the brake? (could be the circuit board/bracket inside the light or an actual wiring issue somewhere else in the car)
^ The board is the thing you plug the actual light into which has the three bulb sockets on it, you can see that some of the electrical routing could be shorted out which would cause this.

• Have you switched the bulb harness/bracket within the light itself and tried switching it with the other side? (this would eliminate the circuit board/bracket and mean that it's a wiring issue somewhere in the front of the car)

 

If it's just one side, it does not sound like the switch or a ground. It sounds like either the wrong bulb or installed wrong, so that the brighter brake light comes on when the lights are switched on. Usually there are a couple offset pegs on the bulb and it should easily go in one-way only, although you can force it in the wrong way.

 

It's been doing it since I put the bulb in, the bulb was burned out when I got the car.

I have not tried switching the bulbs, I will though, it's easy enough.

It stays on regardless of me pushing the brake.

Haven't switched any parts around yet, but will keep it in mind as I work on it this evening, currently at work.

Both bulbs are the exact same, changed both at the same time so they were both fresh.

I will try putting the bulb in the other way, I remember it had pegs on it but didn't even think about it twisting in one way over another.

Thanks for the ideas! I'll report back as soon as I have a chance to tinker with it. I'll try the easy things first. About 4 hours till my shift is over.

 

Winner!

Thanks to everyone for their ideas, I feel so dumb now. Didn't even notice the pegs were offset, I'm used to older cars where they just fit in any way.