Hello, everyone:

I'm having a problem with my GL550 that I never experienced with the GL450 Premier Edition I had a few years ago. On that vehicle, I towed my motorcycle trailer with no problems. All the LED lights on the trailer worked perfectly and no error messages were displayed on the GL's dash. Now on the GL550, when the trailer is connected, the GL goes nuts. The blind-spot monitors on the mirrors light up permanently and ALL the lights on the trailer blink. I have cleaned the 7-4 adapter (purchased at the MB dealer) and even tried it on a friend's 2011 ML350, with the same blinking results. After doing an extensive search on this and other websites, I still need help finding the right adapter to fix the problem. Your advice on the matter would be highly appreciated.

 

Please. Does anyone know of a solution to this problem? I need to use my trailer, but I'm worried about the flashing trailer lights drawing attention, and possibly a traffic citation. Would reprogramming the rear SAM solve this problem? The service advisor at the dealer was clueless.

 

Have you tried one of these adapters for the Trailer's LED lights? It increases the resitance in the trailer wiring circuit to trick the Mercedes into thinking the trailer has standard incandescent light bulbs.
http://www.towready.com/content/prod...575&part=20141

 

Thank you. That is exactly what I had been looking for. The one sold by U-haul was discontinued and multiple web-searches turned up empty. (Maybe I just don't search well enough.) Anyhow, I called a local dealer, as per the instructions on the website, but the adapter hasn't yet reached distributors. I was told to wait a few weeks and try again. Keeping my fingers crossed that this will work. Again, thanks for your help.

 

http://www.usa-trailer-hitches.com/c...y_Adapters,124

 

Thank you very much. I've ordered one. I'll post a F/U after I receive and test it.

 

 

It works! Thanks again for the advice.

 

So get this crap. Total panic mode. I've towed many times with my 2011 GL450, same trailer and 7 to 4 adapter!


I now have a 2012 GL550. Hooked up the trailer and the blind spot indicator stays on and say to check the owners manual. Trailer lights are blinking off and on. WTF!


I call Mercedes as I need to tow the skis to the lake today not when the problem is fixed. Answer is replace the lights with incandescent lights. WTF, this is the 21st century not the cave man days.


Off to the trailer shop. They call Tow Ready who advises to use the adapter 20141 as some German cars are outfitted with sensors that when LED lights are used go nuts.


Part on order, fingers crossed!

 

You just need inline resistors and it should work fine.

 

Part on order. Waiting to test the water with it!


I've never owned such a complicated vehicle. Over engineered is an understatement!


Our prior VW which was a PITA lemon had less quirks than this rolling nightmare! Lots of stuff happens when you plug up, but all for the good vs. this crap!


Ugh...

 

Ok the adapter arrived. The flashing/blinking lights have stopped. Adapter is now installed. Can't use the old one as it's missing the resistor needed to tame this problem.

New problem. Says trailer brake lights on the dash when the turn signals or brake is applied!

Trailer shop is clueless. Mercedes is clueless. etrailer says to add the resistors on top of the adapter. whats going to happen if I hook the trailer on my other vehicles? Are the electrics going to power down as i now have a huge draw on the trailer?

Anyone got a stick of dynamite?

This is so damn stupid I can't see straight!

 

Great post. I just ordered this

http://www.etrailer.com/p-20142.html

Not sure if I'll need it for a 2010 GL550, but we will soon find out.

 

This has been discussed a few times, but yes, the Merc system is trying to figure out if bulbs are out and let you know. Now, you can have the vehicle programmed for LED lights - but if you then want to tow an incandescent-lighted trailer, you have to have it programmed again. I tow many different types of trailers and didn't want to go back to the dealer every time just for that. I bought one of the "trick" adapters and just have the truck set for regular lights.

This is the one I have: Has been working perfect for me for almost a year, now.

On a side note... we should be able to select what type of lighting system we are towing within the driver's information stuff in the dash display!