Troubleshooting Trailer Lights Which are Not Working

Published 12/13/2019

Question:

When my trailer is connected up and engine is running, I have no rear indicators working on car or trailer, brake light s are ok, I have a Kia carnival

asked by: Andrew S

Expert Reply:

If your rear indicators are not working, it's almost certainly a poor ground, so the first thing to do is take a look at your ground connections to make sure they are attached to bare metal surfaces and free of any paint, dirt or corrosion. What is probably happening is the ground isn't strong enough for the load put on it and fixing this can resolve the issue.

After that, refer to your owner's manual to locate any fuses or relays and ensure they are all there and in working order. If they are, in order to determine the specific problem you will need to purchase a circuit tester if you do not have one - the very handy Cordless Circuit Tester # PTW2979 would be my strong recommendation due to how easy it is to use - and test the connector on your vehicle after disconnecting it from your trailer.

Check the wiring going into your harness from your tail lights to see if those wires are carrying the correct signals, if not then the issue is with the vehicle wiring. And since you mentioned your vehicle and trailer rear indicators are not working, I do suspect the issue is with the wiring on your Kia.

I have added links to a pair of help articles on trailer wiring, including a troubleshooting guide which I highly recommend taking a look at.

expert reply by: Kyle S