Running Lights Continually Blowing A Fuse on Trailer

Updated 09/29/2014 | Published 09/27/2014

Question:

Im rewiring a customline boat trailer and the running lights will blow the fuse every time I try to hook it up. Heres where I am: - All the wires and lights are new led - I used stainless steel screws and reamed out the old holes. The screws are tight and new metal to new metal. - The trailer end plug 7 pin is new and wired exactly like the old - I get juice when I test the wire coming out of the plug - The brake wire surge brakes is hooked up - The turn, stop light works fine. The run light function also works fine when I hook the wire directly up to it. As far as the running lights go - every time I hook one up it blows the fuse. Ive tried it on different lights and the problem still happens. I am running the wire directly to a single light in an attempt to see if the light will work. Too much power for a single light? Most of the wiring diagrams show hooking up each side independently and connecting both wires to the single wire coming out of the wire harness. The old running light wires from each side go into a single wire on the harness. Also - I remember when I tore the old wires out there was a wire that went from one side running light to the other along the axle. In one of your wiring diagrams it shows an optionalinch running light wire connecting the two sides along the axle but I cant find any information about how it works. Could this be my problem?

asked by: Steve Z

Expert Reply:

Chances are the running lights are drawing too much current. It's possible but unlikely that LED lights would overload the harness. You may simply have more running lights on your trailer than your car tail light circuit can handle. The best way to correct this is to remove some of the running lights or use a powered trailer harness like part # 119250KIT.

I recommend closely examining the running lamp circuit on your trailer, look for any pinched wires or wire with nicked, worn or cracked insulation that would allow the copper wire inside to short out on the trailer frame. There's a short somewhere that's blowing the fuse. I would also check your running light wire for potential shorts from rubbing on the trailer frame.

Instead of pulling power through the vehicle lights, a powered trailer harness draws a new source of power straight from the car battery. It still connects to the tail light and blinker circuits, but they are used as switches rather than power sources.

If you write back with the year, make and model of your vehicle and tell me what trailer harness you have on it now, I can see what options are available.

I have attached a link regarding frequently asked questions for you as well. Within that link scroll down to view "troubleshoot your trailer wiring" which may help as well.

Furthermore, I have attached a few video and instruction links for you too.

expert reply by: Chris B