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How to Install 7-Way Trailer Connector on 1999 Chevy Silverado 2500


We just bought a used 5th wheel and the wiring on the plugs do not seem to match up. I have a 1999 Chevy Silverado 2500 with factory Tow package and I need to know which color wire goes where ie: White = Ground, Blue = Trailer brake, Black - Power not so sure on the Brown, green red and yellow. I have looked on 5 different sites and they each say something different. I would run a tester on them but both of my testers are not working. Thanks for any help you can give me.


Expert Reply:

Because vehicle wire color coding can vary, even within the same model year, we always recommend wiring by function, not by wire color. At the vehicle assembly plant, if they run out of a particular color of wire, they will not shut down the assembly line and obtain more, they will simply substitute a different wire color. We offer an inexpensive circuit tester, part # 40376, or you can pick one up at a local auto parts store.

Generally speaking, blue is usually output to trailer brakes, white is ground, black is 12-volt accessory power, brown is usually running lights, green is right turn/ brake light and yellow is left turn/brake light. Red is sometimes use for power, or it could be for reverse light circuit.

I will link you to our trailer wiring FAQ article that features a diagram showing how a 7-way trailer connector should be wired. The best way to wire your connector would be to activate each feature (right turn, running light, etc.) and test the wires until you find the one showing current. You have then confirmed the function of that circuit, which can then be attached to the connector according to the wiring diagram I linked to.

You can also test the wires on the fifth wheel connector by using a car battery to apply power to each circuit to confirm it is wired correctly.

expert reply by:
Mike L

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