How to Activate 12-Volt Power Supply Circuit on 7-Way Trailer Connector on Motorhome

Question:

Hello, I bought an etrailer wiring kit for keeping the battery in my tow car charged with power from my motorhome. To complete the installation I need to supply power to a blade in the MH 7-way receptacle. The 7-way appears to have hot blades for lights, only. I found no energized blade for an accessory. Do I need to connect a blade to a fuse tap in the MH fuse box? Im powering a portable brake system with the tow car battery. The MH is a Forest River Sunseeker 2850LE. thank you,

asked by: Greg G

Expert Reply:

I'd be happy to help you with that.

The first thing I'd recommend doing is checking the fuse box. It looks like your motorhome is built on a Ford Van cutaway chassis. In the 2019 Ford E450, for example the fuse for the trailer tow charge relay is in position # 4 in the fuse box, and the fuse is in the # 17 position.

Depending on the model year of the cutaway chassis your motorhome is built upon the fuse location could be different. The fuse box lid should list what fuses and relays are for which circuits, so check any location described as 'trailer tow charge' and make sure the fuse is in place and is not blown.

If you can't find the relevant fuse, you can run the circuit yourself using part # RM-156-75. I've linked to a video showing a typical installation.

expert reply by: Mike L