Troubleshooting Horse Trailer Interior Lights Not Working with 1999 Ford F-250

Question:

Have a 99 Ford F2 50 all the lights work but the interior lights on the horse trailer

asked by: John

Expert Reply:

Most likely the interior lights on your horse trailer are connected to the 12V circuit of the trailer and truck's 7-Way, although you may want to verify this.

If this is the case then there are a couple things you can check but I recommend starting at the truck. You can use a circuit tester like # PTW2992 to make sure you're getting power at the 12V pin on the 7-Way connector at the bumper (1 o'clock position).

If you aren't getting power then you likely have a blown fuse somewhere on the truck. I took a look at the online version of the owner's manual for your 1999 Ford F-250 and there should be a 10 amp fuse located in the #16 position inside the passenger compartment fuse panel tied to this circuit. There is also a 30 amp fuse located in the #16 position and a relay in the #39 position inside the main power distribution box under the hood. Check all of these fuses/relay to make sure they're in good condition and replace as needed.

If you DID get power when testing the 12V circuit on the truck's 7-Way then your best bet will be to simply trace the wiring on the trailer's 7-Way back to where they meet the power wire for the lights. Check for any pinched, damaged, or exposed portions that need to be replaced.

Please just let me know if you continue to have issues and we can keep troubleshooting.

expert reply by: Chris R