Gen 1: Trailer lights all bunged up.

[Fffrank]

New owner of a Gen 1. It's clean. 135k miles. Wiring for the trailer does not seem to have been modified but it's not working reliably. I've taken everything apart and cleaned it and results don't seem to be improving. Sometimes running lights are working. Sometimes one turn signal, sometimes both. Brake lights don't seem to work. Trailer works great hooked up to my other vehicle.

All fuses are good.

Is there an obvious and known failure point for this wiring? Or any suggestions on where to start? The plug from the truck wiring to the truck-side plug were absolutely gooped in dielectric grease so I feel like I'm not the first to have issues with this truck.

 

[Nex]

How is the ground on the trailer side?

 

[Fffrank]

First thing I redid. I can't tell how strong the ground through the ball is but through the harness is good.

 

[Nex]

Ground should be going through the wiring from the 4 pin, not the ball.

 

[Dblex]

So when I purchased my 2014 a month ago, the trailer connections didn't work. The relay and fuse were in the glove box and never installed. I followed the manual and inserted them in 9 & 21. Still nothing. Forums said to check the harness connection underneath the bed above the spare tire. Connection was good then I saw it! the ground was never connected at the factory or the dealer..

you may want to check those out. hope this helps!

 

[MurderedOutSVT]

Grounded balls are bad, according to @Nex