I own a '98 F150 with factory installed towing package. I have used it to haul a utility trailer for about two years. Two days ago, I hooked on to my trailer only to discover that the trailer lights had stopped working. The lights on my truck work perfectly normal. I found a bare wire touching the frame of the trailer and repaired it.

The only thing I could think of was a blown fuse??? I turned to my Owners manual and found the fuse locations. I discovered a blown mini fuse in the Power Distribution box (20amp running lights) and replaced it. Well, this gave me tail lights on the trailer. But still No Brake or Turn signals. I checked the connection on the truck harness plug. The terminals were clean. The ground wire connection is good and clean. I removed the plastic shield from the harness and inspected for broken or frayed wires. Nothing, all looks fine.

The owners manual does not detail the relays (I think they are relays) in the little 1" X 4" rectangular box next to the Power Distribution box...... Does anyone know if any of these is associated with the trailer lighting?

In searching previous posts, I notice that this is not that uncommon an occurrence. The posts that I have reviewed however do not give explanations as to how the problem was solved. I cannot directly e-mail anyone because I have not been a member long enough and do not have enough posts. FRUSTRATING!!

Thanks for any suggestions,
Ken

p.s.
The trailer lights work perfectly when I hooked it to my other truck.

 

WhipsnHorses directed me to a third fuse box that was not mentioned in my owners manual. 20 amp mini fuse blown. Trailer lights operational once again. Thanks so much for the help.
Ken