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Trailer Light Issue

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Hey guys,

My 2000 GMC Sierra has had an issue since I purchased it.  While towing, the left side trailer light does not work. I had previously chocked this up to a trailer with a bad light but I recently replaced the lights on a new to me utility trailer.  This "new" trailer had the same issue with no left side marker light, brake light or blinker. I have checked the fuses as well as changing the bulbs around on the trailer. I have confirmed with another vehicle that the lights work correctly on the trailer.  Yet when I plug my truck in, I only have the right side lights. The right side is bright and working well. My truck has the factory tow package with the 7 pin round style plug. I have taken the plug apart and found no corrosion. Im not sure if a wire got crossed somewhere or if there is a light issue on the truck. Any help or spots to check would be appreciated. I will double check my fuses and make sure that they are all functional. 

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Checked the harness, no problems there either.  I'm not the first person to be in here searching for the problem. Honestly, i've been looking for a reason to upgrade and this might be it.  Either that or im tapping into the taillight harness just to get me by. 


Got it figured out, turned out to be a burnt wire in the trailer harness.  Im guessing it was due to a bad ground.  I cleaned the grounds and fixed the wires.  Hopefully it doesnt repeat. 

Edited by Logan Lanfear
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similar to this:




Just saw you found a bad wire. Good job. Keep the above link handy too, mine ended up failing.

Edited by ChevroletTough
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