I've got a 2005 Chevy 2500HD 4x4. Factory installed is the "7-Round" trailer light plug. I have yet to find a trailer where all the lights work properly. I've tested this on brand new trailers at a dealer, not just on mine and others, so I'm sure it's an issue with my plug. My question is: Is there a common issue with these? I know I can get a test light and go to town tracing connections on my plug wiring and whatnot, and I do plan on doing so relatively soon. I just figured maybe there was a chance someone else had a similar issue and could point me to the right spot to look first to save some time. I have the same issue whether I'm using a trailer with a "7-Round" plug that fits directly into my plug AND when I use my adapter to use a "4-Flat" plug. The brake lights work, hazards work, right turn signal works, but when I hit the left turn signal both trailer lights blink(like my hazards are on) and I have no running lights. Any help would be appreciated. I despise electrical wiring.

 

Probably a faulty light controller. It's in the right rear quarter panel above the exhaust pipe with 4 connectors on it. Crappy location that exposes it to water, dirt and heat.

This doohickey:
http://www.carid.com/2005-chevy-silv...-16404882.html