Running Light Circuit Does NOt Work After Installing New 7-Way Trailer Connector on Vehicle  

Question:

Expert Reply:

What vehicle did you install it on? Did you use something like # 30717 or was it a regular 7-Way, not an adapter? Adapters like this must be grounded using that separate white wire otherwise they will not work properly. Try moving the ground to a different location.

If you happen to have a Nissan then there are some Nissan vehicles that require an additional relay, like the blue ones included in part # C57000, inside the in-cab fuse panel for the running lights. On vehicles that use relays the only way to see if a relay is bad is to use a known good relay and then see if the function is working.

On a 7-Way trailer connector if you are looking at the front of it the running light pin is in the 11:00 position. Use a circuit tester to test that pin while the running lights are on. If it shows power then the issue is on the trailer. If it does not show power you can test the running light wire at the back of the 7-Way and forward to see if it is just a break in the wire somewhere. You can also use the vehicle owners manual to locate any relays related to the tow package wiring.

If the issue is on the trailer it is likely a bad ground and you will need to make sure that the truck side and trailer side connectors are clean and corrosion free inside and out. Make sure the main trailer connector ground and the grounds for all the lights are connected to clean and corrosion free bare metal surfaces.

If the trailer has an aluminum frame, tilt, bed, folding tongue, or if there is a plastic license plate bracket between a ground and the frame any of those things can interrupt the ground. Adding jumper wires from the light grounds to the main trailer connector ground can help.

expert reply by: Michael H

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