Brake lights won’t turn off

[George.Smith]

Someone driving behind me today told me my brake lights weren’t turning off. When I turn on the ignition they’re on, and they stay on whilst I’m driving even when I’m not touching the brake pedal. I took it to a mechanic and he replaced the switch which didn’t fix the problem. After playing around I turned the engine on, and the brake lights weren’t on, but as soon as I pressed the brake pedal they came on and stayed on, even after I’d started driving. I also had a warning come up on the dash saying ‘inoperable’ which turned the traction control lights on, but that went after I turned the engine off then back on. In the manual apparently that has something to do with the braking. The really weird part is I took the fuse out for the rear brake lights, but they were still on when I turned on the ignition?

I have a 2012 C180 petrol Mercedes. If anyone has any ideas please let me know because I’m baffled

 

[M80]

It could be the pedal isn't rising off the switch,
first try pulling the pedal up by hand and see if that works.
It may be the bracket holding the switch needs manipulating, just a bit.

 

[EmilysDad]

Was the new brake light switch fitted correctly? ie was it adjusted correctly?

 

[George.Smith]

It could be the pedal isn't rising off the switch,
first try pulling the pedal up by hand and see if that works.
It may be the bracket holding the switch needs manipulating, just a bit.

Moved the pedal around, and the switch was changed and adjusted at the mechanics but no luck

 

[George.Smith]

Was the new brake light switch fitted correctly? ie was it adjusted correctly?

I presume so! The problem was occurring before I changed the switch

 

[Steve@Avantgarde]

Sounds like a SAM unit fault...

 

[phils]

Reminds me of a similar problem on my Astra B - brake lights permanently on, whenever lights were on. Took it to VX main dealer (it was a company car) and unusually for this dealership, their service manager was very helpful.

He removed both the stop/tail light bulbs and the side light filament on one of them had blown and was touching the stop light filament. So, whenever the lights were on, it was feeding power to the brake lights. Easy fix - 1 new bulb.

I would imaging that the OP's car has LED rear light clusters though?

Phil