Tekonsha P3 brake controller red wire.

[Tgrossman]

2018 Isata 3. I tried wiring in the above brake controller. I found the blue wire under the seat and ran it forward. The black power wire goes to battery and the white goes to negative.

For the red wire out of the controller, I was not able to find the cold side of the brake light switch. There are 4 pink wires on the MB brake light switch, wide black is hot, then there is thin black, thin blue and thin green. None of those would go hot when I depressed the brake pedal while engine is running.

What am I missing? Where are folks tapping in the red wire off their controllers?

UPDATE: etrailer.com comes through again. It is the pink wire with the thin green stripe. Not enough voltage to light up an incandescent test light. That’s why I couldn’t see it.

Thanks.

[Ragtimeplayer]

Do you have an MBS platform? I can’t find a Tekonsha wiring harness for the Mercedes.

[bclemens]

Yes, they went CANbus on everything. Makes things really difficult when we want "trigger wires".

[Iwannacamp]

Maybe an idea... IF you cannot do ANYTHING else. They make stop light switches that are hydraulically activated.. think 50s and 60s cars etc.. I am sure you could find a connection point somewhere without cutting anything.

[Iwannacamp]

Ideas?

https://www.etrailer.com/question-238891.html

https://www.etrailer.com/question-239741.html


Read this thread.. especially #17 and on

Brake Controller 2017 Sprinter Chassis - iRV2 Forums

[bclemens]

I think, if you read his "edit" he has it figured out and all is good.

[Battchief]

I am going down the same road with my 2020 Isata 3 and have decided to order the same controller. Before ordering, I need to know if the trailer connector is MB factory pre-wired or was this done by someone else? I have not looked for the telltale green connector under the seat yet. Has anything changed since Tgrossman installed his controller? Any and all help deeply appreciated.

Thanks

Battchief