Troubleshooting Turn Signal Turning on Trailer Lights

Updated 08/08/2019 | Published 08/07/2019

Question:

When l put my left signal light on all the light on the Trailer start flashing what would cause that

asked by: Chris B

Expert Reply:

There are a couple of reasons why engaging the turn signal would cause your trailer lights to start flashing and the most likely reason is a bad ground. You'll need to make absolutely sure your grounds are attached to bare metal surfaces and free of any paint, dirt or corrosion because if they are not they can cause all types of issues, including the one you are having.

You will also want to check both your vehicle and trailer connectors for corrosion, which can be green or white in color. A build-up of corrosion can interfere with the signals getting through the connectors so if it is present you are going to need to either replace the plug or clean the corrosion.

Finally, check your wiring thoroughly to ensure there are none that are crimped, broken or otherwise damaged. 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