Testing Wires for Function When Hardwiring a 7-Way Trailer Connector on a 1999 Jeep Grand Cherokee

Question:

I have eight wires to connect to a 7 blade plug black, black, black with yellow stripe, brown with red stripe, purple, red, green, blue, how do i direct wire it and what color wire is what???

asked by: Mark J

Expert Reply:

Wiring, and by extension, wiring color, is never an exact science. A company can up and change wiring color even within the same model year. The best way to determine functions of the wires you see is to test them for function with a circuit tester like # PTW2993.

To test the wires using a circuit tester, first turn on the left blinker. Find the wire that carries a signal in unison with the blinker. This is your left turn signal wire. Next, do the same with the right blinker. Then, find the wire that has a constant signal when the lights are on. This is your running light wire. Do not confuse it with the 12-volt hot wire which will have a constant signal when the lights are off.

With the vehicle in reverse (best to have a helper in the vehicle applying the brake while it is in reverse and engage the emergency brake) find the wire that has a constant signal. This is your reverse circuit. The last wire is for the electric brakes. If you have a brake controller installed, have someone engage the manual override on the brake controller. Then just find the wire that carries a signal when the brake controller is engaged. The remaining wire is the ground. To wire these wires into a plug, look at the same FAQ article, about halfway down the page, under 7 Way Vehicle Connector. On the right is the inside, or back of the plug, diagram.

We do have a probable color code for Jeep, but again, it is only a guide, and you should really test the wires to be sure of their function. Not to mention that the colors we have listed do not match what you have on your 1999 Jeep Grand Cherokee. But if you want to give it a once over, I have linked the page below.

expert reply by: Michael H