Installing a 4-Pole Trailer Connector at Rear of 5th Wheel for Towing Boat Trailer

Published 06/15/2016

Question:

I am planning on purchasing the Curt 13703 hitch to mount on the back of my fifth wheel frame. That looks straight forward. Where I am not sure about is what wiring harness I will need to go to a 4 flat for my boat trailer that I am planning on pulling behind the fifth wheel. The fifth wheel is a 2015 Keystone Cougar 28RDB. Any suggestions would be great. Thank you

asked by: Jon L

Expert Reply:

The Curt # 13703 would work fine for you.

To install a 4-pole connector at the rear of your 5th wheel, the easiest option would be to tap a 4 pole vehicle end harness like # 18002 into the taillight circuits of the fifth wheel.

I do have a caveat or two to share, however.

-Keep in mind that towing a trailer behind another isn't legal in many states, and from a safety standpoint it's something we don't recommend.
-You'll need to determine if the tow package of your Silverado has a sufficient rating to handle the draw of the lights on the fifth wheel plus the draw from the lighting on the boat trailer. The running light circuit of your factory tow package is rated at 15 amps, and the stop/turn signal circuit on each side is rated at 10 amps.

Each taillight draws about 2 amps, and clearance or marker lights draw about 0.5 amps each. If the total amp rating of all the lights approaches the rating of the circuit mentioned above, you might consider installing LED lamps on the boat trailer. LED's draw only a fraction of the power of incandescent lamps.

expert reply by: Mike L