Troubleshooting Trailer Wiring on 2004 Ford Explorer Sport Trac

Updated 12/18/2017 | Published 12/15/2017

Question:

Im wondering if someone might be able to help me solve an issue today trying to fix trailer lights on a 2004 Ford Explorer Sport Trac that had the brake and turn signals working when I started, but when I was done I was getting no power at all testing with a light up pointed screwdriver type voltage tester to the trailer harness on the truck side. Im not sure what I did to end up worse off than at the beginning of the fix need. My parents have a night craft show tomorrow and will need lights so I dont know what to do to fix whatever it was that I did wrong and make it all work again. I had just fixed them about two months ago and felt so good about doing it and now I cant seem to figure out how to do it again...help??

asked by: Mark H

Expert Reply:

The first thing I would check on the Explorer are the fuses (and relays) associated with its trailer wiring. I reviewed an online owner's manual but no information about the fuse box (power distribution box) is included so I suggest that you check the lid on the fuse box. Usually these will have a legend that tells you which fuses are related to towing functions. Check to make sure nothing has caused one of these to blow. A short in the trailer wiring could cause a fuse to blow.

If all fuses are okay then check the wiring, from the back of the trailer socket as far forward as you can get access to it. Look for cracked or worn insulation, wires rubbing against moving parts or parts like the exhaust that could damage the wiring. Repair or replace any damaged wire as needed. For a new 4-pole pigtail use # 18252.

Make sure that the main ground wire for the vehicle (and trailer) wiring harnesses is solidly attached
to a clean bare metal surface. A weak ground will cause all sorts of issues with trailer lighting.

Also check the trailer socket itself for signs of damage or corrosion. Over time corrosion can build up on or even inside a trailer connector and cause issues. The same can happen on the trailer side.

You can refer to the linked articles for more troubleshooting help. Once you get things working again you can protect those good connections with dielectric grease like # 11755 which blocks water and dirt from causing corrosion issues.

expert reply by: Adam R