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Both Trailer Turn Signals Come on and Brake Lights Not Working with 2004 Chevy Silverado


When I turn on my left turn signal the right comes on as well on trailer only. Right works fine. I had no electric brakes had to hard wire red into cold side of brake switch. No brake lights on trailer either. Maybe. Turn signal flasher relay?


Expert Reply:

You will want to test the vehicle side trailer connector without the trailer connected to determine if it is a problem on the vehicle side or the trailer side. Use a circuit tester such as # 40376 to test the pins on the vehicle side connector while someone sits in the truck and runs through the various functions.

If the turn signals and brake lights are working fine at the truck's trailer connector then the issue is on the trailer. If the turn signal and brake light circuits are not correct on the truck side then the issue is with the truck wiring.

For the brake lights you can check to make sure the stop light and CHMSL fuses are intact and replace as needed. Also, make sure both the truck and trailer side connectors are clean and free of corrosion inside where the wires attach and on the pins.

If everything checks out on the truck then the issue must be on the trailer. If cleaning the trailer connector does not help then it could be a bad ground. The main connector grounds should be attached to clean and corrosion free bare metal surfaces.

The light grounds should also be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.

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