95 F250 with original factory 7 pin trailer harness. Parking lights work on the trailer, but no stop or turn signals. I checked power distribution box under the hood and fuses 4,6, and 7 are good. I tried swapping relay #4 with 3 spare relays I had but no luck. At the 7 pin connector I have power to parking lights, power to trailer battery, ground. Pretty sure trailer brakes have power also. Anyone have any suggestions? Thanks in advance.

 

Sounds like you have a broken wire on the lead that feeds the brakes and turn signal lights, I would crawl under the truck and trace those two systems, if you can't find it, it would not be difficult to run new wires from the rear of the truck to the plug, one from each light should do it.

 

My guess is that the wires have pulled out in the trailer plug.
If not that check for the wires pulled out in the plug on the truck.

 

I followed the green and yellow from back of truck up to where the harness goes back into cab under the brake master cylinder and have no power when turn signals are on. How does the wiring run from turn signal switch to power distribution box?

 

Does the turn signals on the truck work?

 

All lights work on the truck whether the trailer is connected or disconnected.

 

Sounds like fuse G & F are bad.



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Replaced them both last night. One of them (I think the right turn signal) I get the on off pulse on both sides of the fuse when checking with the test light. When the other signal on I get nothing at the other fuse.

 

It has to be those fuses, dash plugs or wiring.



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Seems like my light green/Orange stripe wire and orange/light blue stripe wire are not getting power to the engine compartment fuse box where it changes to yellow and green wires.

 

Sounds like you have a wiring problem between C205 and C202.
Pins pushed out?

 

Found my issue. Engine compartment harness does not match up to in cab harness at firewall. The large 72 pin (I think) harness has the yellow and green coming from power distribution box and loops in the cab over to the 24 pin (trailer, fuel pumps, rabs etc) harness and straight to 7 pin trailer plug. Cab side green and yellow are locations 61 and 62, engine compartment side they are at 65 and 72. I am gonna cut them and splice today. Now I know where to start looking to get my temp and oil pressure gauges to read properly.... Thanks to Subford for the wiring schematics.

 

Here is a wire routing diagram:


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Finally located the factory fuse box for my 98 F150 on the driver side engine comparment fender well under the hood hinge. Sure enough, the 20Amp mini fuse was blown.

 

Make sure your getting a good ground at your lights.also check see if your getting power to trailor plug. If every thing is working on truck then its all trailor related