Troubleshooting Right Turn Signal Causing Both Trailer Lights to Flash

Published 05/18/2023

Question:

I have 5 x 8 open cargo trailer. It has a 4 pin connector. Lights all work but right turn signal causes both tail lights to flash! Left signal is fine. Brake lights fine and trailer lights all work with truck headlights on. What is my problem?

asked by: Greg F

Expert Reply:

It sounds like your right turn circuit is damaged somehow and is crossing over to the left turn circuit as well. What you'll need to do is check your tow vehicle wiring with a circuit tester so you know if the problem is on the tow vehicle or the trailer. If you turn on your right signal and then test the left turn circuit pin you can see if the signal is jumping over on your tow vehicle or not.

If the problem is on your tow vehicle then you'll need to replace the 4-Way, but if it's on your trailer you'll need to replace the 4-Way and/or other wiring on your trailer.

We have some replacement 4-Way leads for tow vehicles and trailers and this kit from Hopkins # HM48205 has both in case that's the route you need to take.

I'm also attaching a photo showing which functions are on which pins for a 4-Way that you can check out.

expert reply by: Jon G