Brake Controller and Truck Bed 7-Way Trailer Connector for a 1994 GMC Sierra

Question:

Hi, Can you tell me if the ETBC7 7way connector is suitable for in-bed mounting for a gooseneck horse trailer? Do you know why my 1994 GMC Sierra Turbo Diesel 3/4 factory trailer wiring has 2 yellow wires, in addition to dark and light green, brown, and white? Planning Prodigy 2. Any thoughts on existing had a camper west marine 50 combiner-suitable for 7way black trailer has big battery-1990 Sidekick 3 horse? Not sure if it has own charger. Thanks,

asked by: Charles E

Expert Reply:

The 7 and 4 Way Installation Kit, # ETBC7, is the kit we recommend for use at the rear of the vehicle but not for in-bed mounting for a gooseneck trailer. We do have specific 7-Way harnesses for that purpose. You can use the 7-Way Connector 7 foot Loop, # 20027. One end plugs into an existing 7-Way at the rear of the 1994 GMC Sierra and the other end can be mounted in the bed. If you do not already have a 7-Way you will need to install a 4-Way, # 118315, (installation details linked below), and then an ETBC7 kit.

Wiring and wire color is not an exact science among vehicle manufacturers so it is tough to say why GM would make two wires with different functions the same color.

With a 4-Way installed, it would plug into the back of the ETBC7, and the remaining wires would get hardwired to the truck to provide power to the 7-Way, reverse lights, and electric brake functions. The 12 volt pin on the 7-Way (top right pin if looking at the face of the vehicle side connector) would provide power to the trailer battery. You just have to make sure the wiring going to the trailer battery comes from the top left pin if looking at the face of the trailer side connector. All that would be left would be to mount and connect the brake controller # 90885. I have included an FAQ article on hard wiring a brake controller from scratch and 2 videos showing the installation of an ETBC7 harness.

expert reply by: Michael H