Hi there my name is Rob, and I am hoping some of you may be able to help me with an issue. I have a 2004 2wd F-350 super duty with a 5.4 L V8. The truck has a utility bed, and trailer brake. It is bonestock with manual windows, factory am/fm radio, and really no added features. My problem is that my turn signals only work in the back if you flick them multiple times, while braking. The reverse lights come and go randomly. I have no dash or running lights. The only things that are working are the 4-ways, headlights (low and high), brake lights, and cab light. This all started a few months ago when the trailer brake started buzzing randomly, and would only shut off when you braked. I was hauling a trailer, and lost all trailer lights, then four-ways, brake, and low beams. I replaced the flasher, and then lost my turn signals, but regained the 4 ways/headlights/brakes. I have checked every fuse under the dash, replaced the multfuntion switch, and found two lose grounds. I sanded the frame down to the metal, and reconnected them. I noticed heavy corrosion in the trailer harness, and cleaned them as best as I could. I have checked every bulb/light, and looked over the entire electrical system 10 times. As an electrician this has been driving me completely insane not being able to find a solution. Any suggestions, would be greatly appreciated.

(also the trailer brake stopped buzzing, but the red light is on)

 

Rob,
Sorry. I can commiserate. Electrical gremlins can make you NUTS!

Unfortunately, I don't have anything specific to point you to.... but the flakey behavior with the electrical problems shifting around, sounds to me like you've still got a bad ground (or grounds) somewhere. I think you're gonna have to find the ground point(s) for each flakey system and clean them up. The ground may not be loose, but there's probably enough corrosion in the connection to raise its resistance high enough that the return current finds a lower impedance path somewhere else.
I had similar problems with '95 F150 towards the end of its life as it got consumed by rust. Had to make new grounds for backup lights, fuel gauge sensors, and the right headlight.
When you clean up each point, cover it in dielectric grease - it'll help keep water out and slow future corrosion.

[ON EDIT] I think your truck has a GEM (General Electric Module) mounted on firewall under yhe driver's side dash, along with a fuse panel. If your windshield has a leak, water can drip down behind the dash and get into the GEM module, or cause corrosion on the back of the fuse box. This problem is not obvious and has been implicated in lots of cases like yours, It's been known to have driven a lot of truck owners nuts, I reread your post and you mentioned the dash it out - and I sort of remember this being a common theme with the windshield-leak-induced problems.

Good Luck,

RWNJ

PS. Welcome to FTE!

 

"I have no dash or running lights."

My lights went out, I have a 03 F350 XLT. 4x4 with the 5.4L Although mine kept blowing fuses, it came down to a bad headlight switch, I had headlights, I had brake lights but no cab, dash or rear running lights.
You also mentioned that the trailer harness had heavy corrosion. Usually it's best to either buy new and replace the harness or cut it out and replace that section.
I believe also, I read awhile back that there is some sort of a built in fuse or relay on the back of the fuse block under the dash? Did you drop the fuse block and flip it over to see if it was burned or melted?
Did you disconnect the the trailer brake to make sure it wasn't what's causing all the problems?