Is a Brake Controller Plug and Play Wiring Harness Available for a 2003 Mercedes ML 350

Expert Reply:

There is not an aftermarket plug and play brake controller wiring connector available for the 2003 Mercedes ML 350. You may be able to purchase one from the vehicle dealer though.

I spoke with my contact at Tekonsha and his advice is that you should take your Mercedes M Class vehicle to the dealer to have a brake controller installed. The Mercedes vehicles have very sensitive wiring and splicing into the brake circuit or power on the vehicle can cause issues.

If you have wiring experience and are familiar with the use of a circuit tester, you could install a brake controller like the Prodigy P2, # 90885. Find the stop light switch circuit under the dash that is hot only when the brake pedal is pressed. Once that circuit is located splice the red wire from the brake controller to it. Then, run an appropriate length of 10 gauge double bonded wire, # 10-2-1, to the vehicle battery, and install a 30 amp circuit breaker, # PK54530, inline on the power wire. This will power the brake controller and provide an appropriate ground. Finally you will need to run a brake output wire, # 10-1-1, to the back of the vehicle from the blue wire on the brake controller. You will have to locate the brake output wire going into the 7-Way connector and sever it. Tape off the vehicle side of this wire and splice the brake output wire you just ran to the wire going into the connector.

If you decide that you do not want to hard wire a brake controller because of your vehicles sensitive circuitry, we have another option that you could go with. The Tekonsha Prodigy RF Brake Controller, # 90250, mounts on the trailer and only requires a 12 volt power outlet in the cab, for the remote unit, and the 12 volt hot lead, left and right brake and turn signals at the trailer connector.

expert reply by: Bob G