Rear lights wiring mess

[Coldpunk]

89 K5 Silverado package(aka manual everything)

No rear lights on the drivers side. Trailer lights won't work when I hooked them up to my trailer. Passenger side works fine.

I got pulled over, and received a warning, for having a tail light out over the weekend and after looking around back there Ive come to the conclusion that a previous owner has seriously jacked up the wiring back here.

Where should I start to replace the wiring in the rear? I read about a connector behind the bumper on the drivers side, can I disconnect there and buy a new part for the whole rear? I'm completely lost and have no electrical skill. Any points in the right direction would be appreciated. I'll be off to buy a meter first thing in the am as I'm sure that's one thing I don't have that I'll need for this.

 

[Coldpunk]

Stupid harness

Found the wiring diagram in my Haynes manual and found the culprit. The ground had pulled out from the connector completely.

The whole thing is old brittle and just in bad shape all around. Ended up disconnecting the drivers side and trailer hitch wiring from behind the bumper by the frame rail and took it to someone to re-wire. I should have tail lights and trailer lights by the weekend.