04 montana trailer light problem

[Trailerlight]

Greetings all, I have a '04 Montana and I am having an issue with the trailer lights. The Right side works fine, But the left side only seems to signal when the brake is applied. At the 4 pin connector I read 3.5v on the flash which obviously is not enough to illuminate the light (led setup) but when the brake is applied I read 11v and the signal functions. I can not find a repair manual in town so I can see the circuit on paper and I believe it's a grounding issue in the vehicle but I'm wondering if there is any other pieces in the circuit that it could be.
Any insight into this problem is appreciated. Rick.

 

[sergeimoskva]

Hello!
Maybe it will help you. Video + trailer connector diagram
http://www.etrailer.com/Custom-Fit-Vehicle-Wiring/Pontiac/Montana/2004/118355.html?vehicleid=20049896

 

[sergeimoskva]

Hello!
Maybe it will help you. The scheme for the trailer connector.

 

[Steelcity]

did you add the wiring harness ? if so was it a plug in type or did you have to cut and splice ? if you had to cut and splice i would start from there maybe you got a bad left side wire or bad ground ? You also said it is an led set up ,I just installed one on my trailer and they kept saying in the instructions that this is non-polarity sensitive , so I guess there are kits out there that are polarity sensitive . Just a few ideas hope it helps keep us informed .

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[Steelcity]

Also out of curiosity what are you guys towing ? How much weight ?