Troubleshooting 7-Way on Mercedes ML-350 Where Trailer Lights Dont Work
Question:
I just had a new hitch and 7pin connector installed on my Mercedes ML350. I went to tow my boat that is on a trailer with incandescent bulbs and when I hooked everything up the trailer lights wouldnt work. Im told the new trailer hitch and connector is set up for a trailer with LED lights and therefore is not putting out enough power to light the incandescent bulbs. My travel trailer has LED lights so Im OK Is there a solution so that I can tow both trailers with the same vehicle?
asked by: Paul J
Helpful Expert Reply:
If your vehicle is set up to only be able to tow a trailer with incandescent lights. Then you would be able to replace all of the trailers lights with LEDs and it would, in theory, work just fine.
Since we have never heard of a vehicle being only set up to tow a trailer with just LED lights I suspect you may have something else going on. Especially since German vehicles typically have the opposite problem where they don't like LED trailer lights.
First thing you should do at this point is test the 7-way of the wiring harness with a circuit tester part # PTW2993 for voltage on all of the right pins when the taillight signals are being applied. Just like in the video I attached.
If the voltage checks out there but the trailer lights still don't function right then the problem is on the trailer wiring. That would mean that problem is either due to a ground issue or a short issue.
Make sure that the trailer side connector are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces. The light grounds should also be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.
If the problem is on the vehicle side then I would first recommend you double check how the harness is installed on your vehicle, make sure all of the connections are good and tight. You should check all towing related fuses and relays as well.
I also attached a link
Products Referenced in This Question
Product Page this Question was Asked From
Combination LED Trailer Tail Light - Submersible - 6 Function - 11 Diodes - Passenger Side
- Trailer Lights
- Tail Lights
- Rear Reflector
- Side Marker
- Side Reflector
- Stop/Turn/Tail
- Square
- Surface Mount
- Submersible Lights
- LED Light
- 5L x 5W Inch
- Red
- Optronics
more information >
Featured Help Information
Miscellaneous Media
Continue Researching
- Shop: Trailer Hitch
- Shop: Trailer Wiring
- Shop: Curt Powered Tail Light Converter with 4-Pole Flat Trailer Connector
- Shop: Curt Trailer Hitch Receiver - Custom Fit - Class III - 2"
- Shop: 7-Way to 4-Way/5-Way Trailer Adapter for Vehicles with Lamp-Out Sensors Towing Trailers with LEDs
- Shop: Trailer Connector Adapter for Land Rover - 7-Way, Round Pin, European Style to 4-Way Flat
- Shop: 7-Way Trailer Adapter for Towing Trailers with LED Lights
- Q&A: Adapter Recommendation for Mercedes Trailer Wiring to Operate Trailer with LED Lights
- Q&A: Mercedes ML350 Does Not Work with a Trailer that Has LED Tail Lights
- Q&A: Adapter for 2010 Mercedes-Benz GL450 Towing Trailer With LED Lighting to Avoid False Short Indicator
- Shop: Combination LED Trailer Tail Light - Submersible - 6 Function - 11 Diodes - Passenger Side
- Shop: Hook Probe Circuit Tester
- Q&A: Can LED License Plate Light be Wired to Trailer 7-Way and Plugged into a Vehicle 7-Way
- Q&A: Troubleshooting New LED Trailer Tail Lights Not Working as Running Lights
- Q&A: Converting RVST50 Style Trailer Taillight to LED
- Video: Performance Tool Hook Probe Circuit Tester Review
- Video: Blazer Light Buster Backup and Utility Light Review
- Shop: Brake Controller
- Search Results: command
- Search Results: 7 way extension
- Search Results: bargman
- Search Results: command electronics
- Search Results: license plate lights
- Q&A: Recommendation to Add Extra Right Tail Light on Trailer
- Video: Review of Optronics Trailer Wiring - 7 Way Round RV Style Trailer Connector To Blade - A7WCB
- Search Results: advent air
- Search Results: tire iron