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Troubleshooting GMC Truck that Left Turn Signal on 7-Way Stopped Functioning


2006 GMC 3500 dura max - boat trailer lights work except left turn , left turn on truck works but no power at 7 way for left turn power there for every thing else ???


Expert Reply:

Since you have isolated the problem down to the left turn signal on the 7-way on your vehicle the problem is most likely a blown fuse under the hood of your 2006 GMC Sierra 3500. GM vehicles tend to blow fuses easier than the other manufacturers.

Check the fuse box under the hood of your engine on the driver side for the trailer related circuits and replace as needed.

I attached a couple help articles for you to check out as well.

expert reply by:
Jameson C

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Follow up Questions

Jack K.
Unique problem, when left turn is on [2007 GMC Sierra Crew] right turn is faintly on at trailer. [LEDS on Trailer] Changed 7 pin and junction piece on frame near hitch. Does the same on another trailer with LEDS. When left turn is on measured 4-6 volts at right turn side of 7 pin.
Etrailer Expert
Reply from Jon G.

It sounds like you've been testing your connector on your 2007 GMC Sierra. Try using a circuit tester and inspect/test the wiring from the connector as far up to the front of your truck as you can get. The only thing I can think of with those symptoms is that you have some damaged wiring somewhere and the one turn signal is bleeding over to the other one.

Reply from Jack K.

@JonG The issue was a couple things, a. 4 position connector block under chassis near the hitch had corrosion on pins, camper top has 3rd brake light and control module behind tailight was defective and 3rd thing camper light was initially wired wrong. Thanks

Etrailer Expert
Reply from Jon G.

@JackK Glad to hear that you were able to figure out what the problem was! Thanks for sharing!

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