One Side of Trailer Lights Not Working With C35FR

Updated 04/12/2021 | Published 04/08/2021

Products Featured in This Question

7-Way to 4-Way/5-Way Trailer Adapter for Vehicles with Lamp-Out Sensors Towing Trailers with LEDs

(141)

$28.57

Hopkins Endurance Easy-Pull Harness with 4-Pole Flat Trailer Connector - Trailer End - 12" Long

(14)

$6.41

Cordless Circuit Tester

(15)

$19.26

Question:

I purchased the TR20141 from etrailer and when I installed the plug on my 2021 Mercedes Sprinter I received an error on the dash display indicating an issue with the right trailer turn indicator. I hooked up my LED lights and the left side works, break and all. But, the right side,, not. Any suggestions?? Thanks!

asked by: Thomas B

Expert Reply:

Since one side of the trailer lights is working fine, it leads me to believe the issue is something other than the 7-Way to 5-Way/4-Way Trailer Adapter for Vehicles with Lamp-Out Sensors Towing Trailers with LEDs # C35FR.

If this were the issue (if the adapter were not working as intended), then it would reason that there would be faults on both sides with your vehicle. My best guess is that the issue is with the actual trailer wiring, or possibly the connector. Since you have a 2021 Sprinter, it is unlikely to be the vehicle, so let's rule that out. So what you want to do is first just take a look at your trailer connector 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 replace it with 4-Flat # HM48114.

You will also want to test the signals coming out of your 7-way with a circuit tester like # PTW2979, and if those are bad you know the issue is with the trailer wiring so you'll need to inspect it closely for any broken, crimped, or damaged wiring. Finally, make sure your grounds are attached to bare metal surfaces and free of any paint, dirt or corrosion.

I have added a link below to a troubleshooting help article I also recommend taking a look at.

expert reply by: Kyle S