Trailer Lights Stop Working When I Turn The Head Lights On 2014 Mercedes-Benz Sprinter

Published 11/04/2022

Products Featured in This Question

Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

(427)

$53.56

Hook Probe Circuit Tester

(70)

$14.54

Question:

Having an issue with signals staying on solid when headlights are turned on. using Curt 7 pin tester.

asked by: Adam

Expert Reply:

When turning on your 2014 Mercedes-Benz Sprinter's headlights your trailer lights stop working is an indication that you have a ground issue. When your sprinter's headlights are on the highest amperage a draw is placed on the wiring system and a faulty ground will appear. First thing you will need to do is make sure you have good metal to metal contact. If there is any paint or corrosion on the bare metal it will act as an insulator. I would check all the ground connections on the trailer as well.

I would check the ground connections in this order start at the trailer tongue. Take the ground loose and clean the connection point on the trailer and wire end. Next I would look into the trailer's tail lights. A lot of tail lights will be grounded through the mounting bolts that attach to the trailer frame. Make sure the connections are clean and solid.

It also could be that you have a short somewhere. Using The Circuit Tester # PTW2993 you can check for the short or see if there is any frayed wiring that could be contacting bare metal or possibly nearby wires.

I attached a review video link below.

expert reply by: Noah E