Can the P3 Brake Controller be Install on a 2015 Mercedes GLK 250

Updated 07/11/2016 | Published 07/08/2016

Products Featured in This Question

Wiring Kit for 2, 4, 6, and 8 Brake Electric Trailer Brake Controllers

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$57.19

Hook Probe Circuit Tester

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$14.40

Question:

I have a dealer installed Mercedes tow hitch installed on 2015 GLK 250 not original from factory. Technician at a local RV center said there were only 6 wires going to 7 pin connector not 7 and is missing the brake wire to activate the brakes on my tear trailer. What do I need to do to install the P3 brake controller to my existing setup? Is there a wiring kit that I need to purchase.? I called the Mercedes dealer who installed the hitch and they appear clueless as what i am talking about. :

asked by: Dale D

Expert Reply:

If you do not have the brake controller already then, I actually recommend going with the Curt Echo Mobile # C51180, for a few reasons. First, it does not require that the 7-Way on the vehicle has the brake output circuit so you would not have to add that line. The second reason is that you will not have to hardwire anything on the vehicle like you would with an in-cab brake controller. And the third reason is that the connection in the vehicle for the red wire can be difficult or even non-existent on Mercedes vehicles.

If you want to hardwire in a brake controller, then the first step is to figure out if there is the proper wire for the brake controller red wire. You need a dedicated brake light only circuit for the red wire that only has power when the brake pedal is pressed. You can test the wires on the brake switch, usually located above the brake pedal, with a circuit tester such as # PTW2993 to see if there is a wire that meets that description. If there isn't then I recommend going with the Curt Echo for sure.

The other wires on an in-cab controller are white for ground (to battery negative terminal), black for power (connect to battery positive terminal via a 30-amp circuit breaker), and blue is output to the trailer brakes. For wiring and circuit breakers in a kit use # 5506.

But if it were me, I would avoid all of that and use the Curt Echo Mobile # C51180.

expert reply by: Michael H