04 f-350 Trailer Signals/Brake lights not working

[rickstricks]

I have an interesting problem I wanted to see if anyone could shed some light on. I recently purchased an 04 350 superduty and the factory trailer plug had been stolen. I finally got one for it, but when I hooked my trailer up all I get is running lights. Here's what I've checked thus far. I have a good ground at the 4 way and the 7 to the frame, I've got 12v running light power on the 4 and the 7, I've got the 12v constant on the 7 and 12v for trailer brakes on the 7. The relays under the steering wheel and the hood are all kicking on when the signals are on. And all associated fuses under the steering column are good. I only found one small 10amp fuse in the relay box under the hood and it was good also. I'm getting no power for signals or brakes back at either plug. If anyone has had this problem and was able to figure it out, I'd be very grateful to hear what you found. I've got a trip coming up in July and would sure like to resolve this beforehand without having to splice into my main wiring.

 

[Dirtleg]

I recently went through mine due to inoperational lights on my trailer that turned out to be a trailer issue not the truck. But if I remember correctly there is more than 1 fuse associated with the trailer in the engine compartment fuse box. I would check for you but my wife has the truck at the moment.

It was surprising that the trailer fuses were so scattered around on this truck. My 97 Club Wagon and 93 F350 seemed to be better thought out in this area.

My advice would be to go through the fuses again thoroughly and then start checking for broken wires.

Perhaps the PO removed the fuses after the plug was stolen to prevent arcing across the wires. Or it's possible that he didn't and the wires burned out.

Good Luck and let us know what you find.

 

[sassyrel]

IFFFF, you have factory trailer tow---then there should be 7 other wires back there for the rv type factory plug. if not, someones bastardized it--i/e wacked wires, and if thats the case--youll have to back up to where the wires are good, keeping the wire gauge the same. colors no make--so long as you have them indexed right!!!! and yes--theres a standardized wiring diagram for that plug---and use heat shrink butt connectors--i dont need to eggsplain--

 

[rickstricks]

It still had the factory plug in place, so this new 7way and 4flat that I bought just plugged right into the stock tow package harness. None of the wires have been cut off. There are three fuse slots in the relay box under the hood, but 2 of them don't even have sockets. They appear to be just spare fuse holders. Either that or they have been damaged. I'm going to check the wires coming out of the relay box to see where exactly they are getting power from. Maybe those fuse sockets need to be repaired?