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Troubleshooting Running Lights and Brakes Not Working Correctly on a Haulmark Trailer


I have a 2006 Chevrolet silverado.It has a Polak connector from the truck. The trailer has a Bargman connector. For some reason, everything works except the running lights, and the brake doesnt work right. Can you help with a suggestion.


Expert Reply:

The problem with the running lights not working could be several things. The first thing I would check is to make sure the 7-Way on your 2006 Chevy Silverado is getting a signal for the running lights. Using a circuit tester like # 40376, test the running light circuit which should be the pin in the 11 oclock position if looking at the face of the plug.

If the signal is coming through, make sure that the corresponding pin on the trailer side (pin in the 1 oclock position if looking at the face) is connected to the running lights. If not, it will need to be. If there is no signal coming through then the problem is on the truck side.

It is possible that you will need to make sure connections under the hood and/or add some fuses or relays. I have included links to a wiring FAQ article and an article that discusses making the connections under the hood. You can also use your owners manual to find fuse/relay location associated with towing.

If everything on the truck checks out, then the problem is on the trailer side. Most likely, the problem is a bad ground or dirt/corrosion in the connector. Check the trailer and vehicle side connectors and clean out any dirt/corrosion. Make sure the trailer ground from the plug is connected to a clean and corrosion free bare metal surface. Finally, make sure the trailer tail lights are also grounded to a spot free of dirt/corrosion.

The brakes not working properly could also be a ground issue. You can check the ground connection from the brake magnets to make sure it is attached in an ideal location. You can also visually inspect the magnets for wear. If you can see any of the windings of the magnets coming through, they will need to be replaced.

I also recommend checking and possibly resetting the brake controller for best performance according to its instructions.

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