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Testing a Vehicle Side 7-Way Trailer Connector for Proper Function  


How is checking a trailer connector done, specifically, and what tools are needed? I have a probe/clip/light tester circuit and a voltage tester with the black/red probes, and box with a dial on the side and a knob with different settings on the front. Will either of these items work?


Expert Reply:

To check the pins on the vehicle side 7-Way, you can use a circuit tester or the volt meter. The circuit tester will show you if a signal is coming through on the pin you are testing while the volt meter will tell you that and how much voltage is being sent. When you test the brake circuit pin on the 7-Way, it may be more beneficial to see how much voltage it is sending through.

If you are facing the 7-Way, using either tester, you will test for the proper signal as follows:

1 oclock position = 12 volt hot lead
3 oclock position = right turn/brake light
5 oclock position = brake controller output
7 oclock position = ground
9 oclock position = left turn/brake light
11 oclock position = tail and running lights
Center = reverse lights

You will need to have someone sit in the truck and run through each function while you test the pins. In order to determine the configuration on the trailer side, you will have to trace the wiring back from each pin. You an use the wiring diagrams I have linked for you.

While checking the connectors if you notice any corrosion build up or dirt inside or or in back of either connector, clean it out. A wire brush like a battery terminal brush works well.

You can also check the adjustment on the brakes to make sure they are not adjusted too tight. There is a a little wheel with teeth in it at the bottom back side of each assembly. Using a flathead screwdriver you can turn the wheel to adjust the brakes. I have included a link to a video that features our installer adjusting the brakes. Go to the 4 minute, 55 second mark.

expert reply by:
Michael H

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