I'm not very tech savvy so hopefully my question isn't too confusing. We have a 2011 GL450 with the factory installed tow package. We pull a 25 foot camping travel trailer and have never had any issues with the lights, turn signals hazards or brake lights on the trailer once plugged into the vehicle.
This past weekend, I attempted to tow our enclosed utility trailer with the GL (usually use my other vehicle) but had a problem with the lights once I attached it to the trailer hitch and plugged it into the GL electrical outlet. Here's the problem I experienced.
When I attached the camping travel trailer to the hitch and plugged in the power cord to the power outlet on our GL, all the lights, brake lights and turn signals worked fine on both the travel trailer and the GL. I disconnected the camping travel trailer and hooked up the utility trailer and plugged it in to the power outlet on the GL. Once plugged into the GL, the brake lights on the utility trailer came on without the brake pedal even being pressed and remained on. The turn signals, hazard lights and trailer running lights (the lights over the wheel fenders and along the top of the utility trailer) did not come on. However, the brake lights, hazard lights and turn signals worked fine on the GL
I took it to our local RV dealer and they checked (tested) the power outlet on the GL and found nothing wrong with it. The brake lights, turn signals and hazard lights all worked when he tested it on his tester. So, I went home and hooked up the utility trailer to my vehicle (my vehicle is used to tow the utility trailer) as well as the camping travel trailer and everything worked fine on the vehicle and both the camping travel trailer and utility trailer.
Puzzled at this point, I proceeded to hook the camping travel trailer back up to the GL once more and everything worked fine. I then hooked up the utility trailer one more time to the GL and the problem still exists (only the brake lights come on without the brake pedal being pressed and stay on). The running lights, turn signals and hazard lights don't come on, on the utility trailer but the work fine on the GL.
Sorry for the long winded post but I am stumped as to why the lights won't work on the utility trailer when connected to the GL and only the brake lights on the utility trailer come on and remain on, even when the brake pedal in the GL is not being pressed. Does anyone have any idea what might be happening? Could it be a fuse? I have know idea. Any assistance would be most appreciated.