On my 1997 Lariat F150 with 4.6 ltr engine I only have power on the brown wire of the trailer connector underneath the rear bumper of the truck. No blinkers and no brake lights on the trailer. Everything works on the truck. I doubt that it is a wiring problem but rather a fuse problem, but I don't know what fuse I should check. Anybody have any suggestions what this could be? Thanks!
I did some more testing. I checked the ground pin on the connector and it is good, so is the brown wire. It has power when head lights are turned on. I rubbed my volt meter probe hard against the yellow and green wires on the connector but no voltage on either one of them. I checked all the fuses in the fuse box under the hood and paid special attention to any fuse that included the word trailer. They were all good. I assume that the tow package connector with its wire harness is on its own circuit and I also assume that it has one or more fuses. It would help tremendously if someone could tell me what fuses serve the tow package harness (if any) and also have a diagram, so I can troubleshoot/trace each wire from connector to where ever its ends

 

1997 fuse box diagram

You have check the ground screw tucked inside the driver’s side frame rail by the spare tire? I have seen those get caked with dirt and whatnot and lose ground. The wiring harness to the rear lights and tow plug sits there as well. Get some safety glasses on and start looking for buggered connections if the fuses aren’t present…which they should be, since even the flat 4 plug would use them in non-tow package trucks.

 

Yes, you could be like me. Drop the spare tire to look and Holy $€☆%! The whole frame and cross supports are just rust. The tow hitch is holding it together!

Yes, that was a joyous day.

 

https://fuse-box.info/ford/ford-f-15...uses-and-relay

 

I will get to it in a few days. We are in the middle of a cold wave, lower 20ties at night. It's bitchin' cold LOL!

 

melk81, thanks for the link to the diagrams. I looked at them and I checked already all the fuses in the fuse distribution box under the hood and they are all fine. I checked ALL of them while I was at it. And then I saw in the diagram the mini fuse panel behind it and in it was fuse #2 a 20A fuse for the trailer stop and blinker lights. And I said to myself " that's got to be it". On my connector on the truck the brown wire (which is for the running tail lights) has power but not the green and yellow wires for the blinkers and brake lights. All excited I jump on it and open the mini fuse box and what do I see??? All I could say was WTF. Can anybody explain this? These things look more like relays than fuses. So what now? Where is the #2 fuse described in the diagram, which could very well be the problem if I ever find it - LOL. Btw. I tested the trailer lights on my brother's truck and they all work just fine. The problem lies definitely with the truck.