Using the Prodigy RF Trailer Brake Controller with a 2014 Mercedes GLK with 7-Way but Only 4 Wires  

Question:

Helpful Expert Reply:

If I understand correctly, your 2014 Mercedes GLK has a 7-Way trailer connector, but it only has 4 wires going to it. That should mean you only have the basic lighting functions: right turn/brake, left turn/brake, and running lights. You can use a meter or circuit tester such as # PTW2993, to see if there really those functions are just by testing the pins while someone goes through the lighting functions. I have linked a wiring article that includes diagrams and functions of various connectors for you to view.

Even if you only have the basic lighting functions you can still get the Prodigy RF to work. You will need about 20 feet of wire # 10-1-1 and a 40-amp circuit breaker, # PK54540. You will attach one end of the wire to the back of the 7-Way in the 11:00 position. Then route it under the vehicle, avoiding areas that may pinch or burn the wire, to the front of the vehicle, up into the engine compartment near the battery. Use wire ties to secure the wire to the frame or an OEM harness.

Next mount the circuit breaker to the metal of the engine compartment near the battery. Pull the wire to the AUX post and remove any excess wire. Attach the end to the AUX post. Then with the remaining wire, attach one end to the BAT post and the other end to the positive battery terminal.

The RF only needs the light functions and 12-volt power to function so this is the easiest solution if your 7-Way is not fully functional. There can be some pairing problems with the Mercedes and the RF. To get around this have another vehicle with functioning 7-Way parked right next to the Mercedes and use it to pair with the RF. Then just move the handheld unit into the Mercedes.

expert reply by: Michael H

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