Troubleshooting Fuses Blowing on Trailer Right Stop/Turn Circuit on 2014 Ram 1500

Updated 07/17/2017 | Published 07/15/2017

Question:

2014 ram 1500 with factory trailer controller. Brand new 14 ft 7000#gvw box trailer. The 20 amp fuse that is dedicated for the right trailer turn signal and brake light will blow only under these conditions If i have the brake controller set a 0inch which means it wont apply any brakes to the trailer the fuse doesnt blow thus all lights work. As soon as I turn up the brake to even a .5 setting, after a few stops the fuse blows that work the right turn signal/brake light on the trailer. However, the brakes still function properly. I have another trailer that is a 10 year old flat bed 7000# gvw with led lights and everything works fine without blowing any fuses. What I dont understand is I can run the trailer all day without blowing that fuse as long as the brakes are set at 0inch but as soon as I turn up the setting on the brakes it blows that fuse which work the right side turn signals on the trailer. Any thoughts?

asked by: Brad E

Expert Reply:

There are two primary possibilities for the issue you're having with the truck's trailer lighting fuses blowing.

One is a short on the truck wiring for the right-side stop/turn light circuit. Check that wire for any signs of damage such as worn or cracked insulation and for any points along its path where it might rub against metal surfaces. A short from this simple issue would blow the fuse.

Another possibility is that there could be corrosive build-up inside the truck's trailer socket. On a 7-way the contact for the right stop/turn is at the 3-o-clock position as you look at the socket (see linked photo, please) and this is adjacent to the contact for the brake circuit. A short between these circuits - from a piece of foreign material or internal corrosion - could bridge the circuits and blow the fuse by sending the brake controller output into the stop/turn circuit.

If you can borrow either a truck or trailer known to be functional you can substitute one at a time to see if the issue remains. Since your trailer is new I am inclined to think the issue is on the truck side but there is no guarantee so it is best to try to test both.

expert reply by: Adam R