Troubleshooting Trailer Interior Lights Not Working When Connected to 2017 Ford F-250

Published 02/22/2019

Question:

We recently got a new horse trailer and the lights on the outside of the trailer running lights, turn signals, brake lights, etc. all work fine. However the I cant get the lights on the inside of the trailer to work operated by a switch inside the trailer. Any thoughts on what steps I need to take to get the lights on the inside to work? I know its not an issue with the trailer because we hooked it up to another truck and the inside lights worked. Thanks.

asked by: Gregor M

Expert Reply:

From what you described it doesn't sound like you have 12V power coming from the 7-Way, like part # HM40975, on your 2017 Ford F-250 Super Duty. Since this is a newer pickup your best bet is to check any fuses or relays related to this function.

I looked up the online version of the owner's manual for your 2017 F-250 and it looks like fuse position 27 in the power distribution box (located in the engine compartment) is the fuse location for the 12V power. If you don't have one in that location then that would explain why you don't have 12V power. It also looks like a possible relay location for the 12V power is location 37 in the power distribution box as well. Check to make sure that there is something in these locations and that it is in good working order. Chances are that's your problem.

expert reply by: Jon G