Troubleshooting 2002 Chevy Silverado Trailer Running Lights Not working

Question:

My trucks running lights arent working. I do have my blinkers, hazards, and breaks. I have checked the fuse box for bad fuses but all of them are good. my truck is a 7 pin but my trailer is a 4 pin so I bought an adapter from AutoZone that has the test lights on it. When I plug in the adapter to the truck and turn on my running lights the test light for the running lights illuminates. As soon as I plug my trailer into the other side of the adapter the test light goes out. I tested the voltage at the adapter and it reads out at 8 volts. I checked the trailers wiring to make sure it wasnt that by hooking it up to another vehicle and everything worked as expected. Ive narrowed it down to my trucks wiring somewhere but cant figure out why it has voltage until I plug in the trailer and why it only has 8 volts. it should have roughly 12 right?

asked by: Thomas

Expert Reply:

Since your tester works for your running lights and your trailer works, you can determine the issue is the connection between the two.

The adapter doesn't seem to be the issue as you have the other functions, which leads me to believe the issue is with your trailer ground wire or a ground wire on your truck side. Sometimes a bad ground will allow function with another vehicle that may have a stronger output so it could be your trailer side, but if you tested your truck and are only getting 8 volts versus the 12 it should be getting, it most likely is on your truck side as you stated. That voltage drop can be from a ground that is corroded or rusted or it could be from a short or even a fray in the wire.

expert reply by: Jason S