Troubleshooting Trailer Wiring that Stops Functioning When Vehicle Headlights are Put On

Question:

both turn indicators work fine, tail lights work but when you turn on the headlights, the turn indicators do not work This is a 1996 GMC truck. Problem is not with the trailer, when connected to my 2002 Tahoe, everything works perfect

asked by: Ken S

Expert Reply:

Weak grounds issues on trailer wiring can manifest when connected to one vehicle but not when connected to another. If one vehicle happens to have weaker trailer wiring circuits than another things can act differently.

Try improving the grounds of your trailer light assemblies as that is most likely the problem. A weak ground circuit can cause certain circuits to not function properly when the added load of the headlights are on. We see this problem all the time and the solution is almost always improving the grounds of the light assemblies or ground strap of the trailer. I attached a help article on troubleshooting trailer wiring for you to check out as well.

expert reply by: Jameson C