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How to Wire Up New Trailer Wiring Connector on Truck with Non-Standard Wire Colors


There are 7 wires coming from my 2005 gmc I cant seem get all the lights working on my trailer cant find the wiring diagram on how to hook the wires. I tried all the wiring diagrams nothing is working .


Expert Reply:

Vehicle manufacturers rarely follow the color codes that are used for standard trailer wiring applications so if all you have is a bundle of wires that you need to wire to a 7-way like the part # HM40975 your best option is going to be to test all of the wires with a circuit tester like part # PTW2993 so that you can determine all of the wiring functions and then wire accordingly to the 7-way wiring diagram I attached to this page.

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expert reply by:
Jameson C

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