Troubleshooting No Interior Lights or Brakes on 2004 Horse Trailer with Mouse Chewed Wiring

Question:

Howdy, I just recently purchased a 2004 Featherlite horse trailer. My tow vehicle is a 2000 F350 with factory installed 7 pin round rv plug. All fuses installed and have hot power on the 1 oclock position. This truck has pulled several trailers with no electrical problems. I have all lights working correctly except for cargo lights and yes the key is on for power. My brakes are also not energizing as my tekonsha controller displays only a dot. I installed a new trailer plug as the old one was beat up and wired it according to the diagram. The new plug did not solve the problem. So upon further investigation I found mouse eaten wires up in the rear corners of the trailer. All wires are intact so I tape and sealed them and no fuses had been blown. So with no interior lights and brakes not functioning I reversed the blue and red wire on the trailer plug and now the brake controller display strength when using the manual slide but displays 0.0 when brake pedal is pushed. Strange and still no interior lights. I have confirmed all interior bulbs work by hot wiring them. I have another trailer and everthing works as it should. Could the breakaway system be causing this? Im stumped at this point and have walked away from it as I have spent several hours trouble shooting and no result.

asked by: Lawrence C

Expert Reply:

Looking at the picture you attached most likely the issue you are having with the interior lights and brakes have to do with damaged wiring. The wiring appears to be damaged enough that just sealing the exposed areas won't quite be enough. I recommend starting by replacing these sections completely with new wiring. You may want to try and inspect any other accessible wiring along the length of the trailer for similar damage as the mice in question may have found other tasty sections as well.

Then check the wiring coming from the brake assemblies themselves to make sure they are still in good condition and that the ground wire from each assembly is secured to a clean, rust free metal surface on the trailer frame. On an older trailer like this it is probably a good idea to go and and remove the ground wires, sand down the frame surface, and reattach them.

I do not think the breakaway switch wiring on the trailer is related to the problems you are having. If the above does not resolve the issue please let me know and we can continue to troubleshoot.

expert reply by: Chris R