Troubleshooting 7-way On 2004 Ford F150 Not Showing Left Turn Signal  

Question:

Helpful Expert Reply:

If you've tested the 7-way on the vehicle, and have determined that you have no signal on the left turn signal pin, closely examine the trailer connector. Make sure it's not damaged or excessively corroded and clean/replace if necessary.

If the trailer connector checks out okay, take a look at the wiring harness that feeds the 7-way, right behind the connector. Find the yellow wire in the harness and use a circuit tester like part # PTW2993 to test the wire as a helper activates the left turn signal. If you show current on the yellow wire, the 7-way is faulty and it should be replaced. You should be able to unplug it from the wiring harness and install a replacement like part # HM40975.

If you get no signal on the wire, you've most likely got a blown fuse. Check the owner's manual for the location of the tow package fuse for the right turn signal. Once you replace the fuse, but before plugging in the trailer, you'll want to closely examine the left turn lamp circuit on the trailer to find the short that blew the fuse in the first place. Look for pinched wires or loose connections. Check the wire insulation to make sure its in good shape, not worn or cracked. If you don't fix the short, you'll continue to blow fuses.

I'll link you to our trailer wiring troubleshooting article, which I hope you'll find helpful.

expert reply by: Mike L

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