How Can I Add Aux Power When Using My 4-Way Harness to Power My Trailer Lights?

Question:

Both my trailers use a 4-wire connection, including a 6x12 that has interior lights. Those lights only work when the car is on, running or in accessory mode. So, my question is whether a 7-wire connectors accessory wire is hot all the time or just when car is in acc mode. If ‘hot all the time’ - is there any ‘7 to 4 wire adapter’ that provides a 4-wire connection AND an aux wire so I can run it to my interior lights. Fused would be nice, since it’s presumably a direct battery connection.

asked by: Rob M

Expert Reply:

The best option for you is to add a 7-way connector to your 4-way harnesses you already have installed. This way, you will have access for an auxiliary source. While most factory 7-way harnesses do not have power when the vehicle is turned off, the kit we have provides you with a "hot all the time" power source. That is the Universal Installation Kit for Trailer Brake Controller - 7-Way RV and 4-Way Flat - 10 Gauge Wires # ETBC7.

In order to use this, you need a 7-way plug on the trailer's side. For that part, that is the 7-Way Molded Trailer Wire Connector - 3' Long # H20042.

expert reply by: Bob C