Turn Signal/trailer Light Problems

[BrockwayMT]

2004 K1500 Regular Cab WT

 

I have two problems here that I think are one in the same.

 

1) Every so often when I put on the right turn signal I will get both. Usually goes away after a little while. I thought it may be a short in the plow harness or the trailer light plug. I went through both to make sure they was no water or corrosion. Trailer and plow plugs are full of grease to prevent shorts.

 

2) Trailer brake lights do not work. Sometimes left brake light doesn't work, sometimes both don't work. This has happened with two trailers, one with a 4 pin connector and one with a 7. In both cases the trailer turn signals work so I know it isn't the trailer bulbs or a ground issue. Brake lights on the truck work fine.

 

I've been studying the wiring diagrams on Alldata. I think it is the Turn Signal / Hazard Flasher module.

 

Any ideas? Seen this problem before?

[bill190]

I would follow the wiring from the back trailer connector up under the truck wherever it goes and disconnect/clean all connectors and examine all wiring.

 

I would bet that where your stop light problem is would be the same spot your left/right intermittent short is!

 

For the stop light problem, you can get an assistant to press on the brake, or if no assistant, a heavy brick will do the job! Then you can use a multimeter along with the wiring diagrams to test the stop light wire at various points.

 

The problem is always something simple, just a matter of finding it! (Not so easy...)

[BrockwayMT]

I don't think there is a left to right short as the right blinker gives both but the left blinker gives only left. Usually a short like that would work both ways. Bad grounds can make some crazy things like that happen though. Next time the blinker acts up I am going to pull the trailer turn fuses to see if that cures the problem. If it does I'll know it's in the trailer plug wiring.