Troubleshooting Turn Signals on High/Low Trailer  

Question:

Expert Reply:

What exactly do you mean by 'they are on when I brake or turn on my signals they do not work'?


I'm assuming the turn signals/brake lamps work okay on the tow vehicle, just not on the trailer, is that correct?

You'll want to begin by using a circuit tester like # PTW2993 on the pins of the trailer connector and test it. This will tell you whether the problem exists on the trailer or on the vehicle. Or, if you can try the trailer on a different vehicle or the vehicle on a different trailer that can help rule things out as well.

Have a helper activate the right turn signal on the tow vehicle. Then ground the tester and probe the pin in the 3:00 position in the 7-way trailer connector. The tester should pulse along with the turn signals and should illuminate when the helper steps on the brake. Then, activate the left turn signal and check the pin in the 9:00 position, the tester should also blink and light up with the brake pedal. If it does not, you likely have a blown fuse. Find the fuse and replace. If the pins on the trailer connector test okay, the problem is likely on the trailer.

Check the right turn/left turn signal/brake lamp circuits on the trailer, trace them from the trailer connector all the way back to the lamps. Look for loose connections or broken wires. Check the ground connection where the white wire from the trailer connector attaches to the trailer frame, usually on the trailer tongue. Make sure this connection is secure and not corroded. I've linked to some help articles about trailer wiring, and if you'd care to reply with more specifics about what you have going on, I'd be happy to assist.

expert reply by: Mike L

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