Rear brake lights issue...this is a wierd one!?!

[Sidneyjames]

The top rear brake lights don’t work on my 2009 e70. Bulbs are both fine. I know this because when I take out the lower brake light bulb (the one in the same chamber as the LED strip) and then press the brakes the top brake light bulb works. Same for both sides. But..soon as I put the bulbs back in for the lower brake light, that will work but the top brake light bulb will not come on! I’m totally baffled .
Ps when I say lower brake light bulb, I mean the one on the middle section of the rear lights!

Can anyone help? A mate of mine reckons it’s something to do with power distribution..when the lower brake light bulb is in, all the power is sent to that and there’s not enough to power the top bulb however when the lower is removed all the power goes to the top, sounds confusing?? How do u think I feel right now!!!!!

[mr angry]

I remember spending hours with what I thought was an issue on my e53 rear brake lights. It transpired that only one of the bulbs lit on each side under normal braking. When emergency braking both sets were designed to illuminate......I think that was correct. Could this be similar?

[Sidneyjames]

Maybe...not too sure. Need to go on a drive and find an x5 to get behind when he brakes and have a look. I’m sure that both used to work before!

[X5Sport]

Your handbook should tell you how they work.

[rehan]

Hi,

Mine was the same. Had a warning on the computer to say one brake light was out. Checked round the back, and on the side where it was reported faulty, the upper one was illuminated. Looks to be a backup brake light to me, but I would think it makes sense for the upper ones to come on in an emergency too. If there's a way to code the car for all 4 to come on during normal braking, would it be a good idea to do this change?

[Sidneyjames]

Yeah turns out it’s an emergency backup light in case the normal brake lights fail. Stupid really but that’s BM’s!