2010 GLK350 Aftermarket hitch CURT wiring

[johny-rock]

Hi to all,

I installed a CURT hitch on my 2010 GLK350 and everything went well but now I am puzzled with the wiring for about a week now. I have a Canadian car with daytime running lights if that matters.

The recommended converter is CURT 56200 which I installed first. LEFT (yellow) and RIGHT (green) turns signals work perfectly. However, my TAIL/BRAKE (brown) stays always ON. I am pretty sure I used the correct wire (pink wire on driver side harness).

When testing this wire (pink MB harness before the converter) with a lamp :
- Step on the brake : High intensity
- No step on the brake : Low intensity

When testing converter output (brown) with a lamp :
- Step on the brake : High intensity
- No step on the brake : High intensity

I called CURT technical support and spoke with a technician over there. By the way, they have an amazing unit and they sent me a replacement unit very quickly. They also informed me that the 56200 is discontinued and sent me a 56236 unit.

Unfortunately, the new 56236 have exactly the same behavior so I don’t suspect a bad converter anymore.

You guys have any ideas?
(Attached is the wiring diagram from Xentry)

Thanks for your help !