Troubleshooting Trailer Lights Not Working with Headlights on 2010 Mercedes-Benz M-Class Bluetech

Question:

Hello, I have a 2010 Mercedes Benz M Class Bluetech that I am trying to connect my trailer to. I am having an issue with the lighting, when I turn my lights on the trailer lights stop working so I have been unable to haul things after dark. Any insight on what I need to fix this? Thank you for your help!

asked by: Katy K

Expert Reply:

So the problem that you're experiencing has to do with either a bad ground OR your trailer lights are overloading your vehicle circuits. The first thing to do is to check all of your grounds on your trailer and your vehicle side that are related to the lights. Make sure that they are securely connected to a clean, bare-metal surface. Rust, corrosion, or even some paint can cause a bad ground connection.

If all of those look good then we'll need to move on to your circuits being overloaded.I'm thinking you have a wiring kit that pulls power directly from your OEM wiring circuits so I recommend using a wiring kit that pulls power directly from your vehicle battery like the Tekonsha ZCI # 119250KIT that just clamps onto your OEM wiring and doesn't require splicing, or the Curt Kit # C59496 which does require splicing.

The only other way to keep overloading your circuits would be to disconnect some of your trailer lights, but you'll want to make sure that your trailer is still legal in regards to the lighting.

I have attached some helpful articles for you to check out as well.

expert reply by: Jon G