Proteus7

Just took delivery of my new ML350BTC, in pearl beige (one of the last ones apparently). Thanks to all the folks on the board for the ordering tips, the upholstered dash/brown ash combo looks amazing! I have the factory hitch.

Now, I just need to get a brake controller installed, and figure out how much trailer I can tow. From all accounts, the Prodigy 3 seems to be the way to go. Is there anyone in the Seattle area who has been through this before, and can make some recommendations on a good RV shop (or dealer) who knows how to do this? I've gone to a few RV dealers, and nobody seems to know anything about the ML (I just tell them its a fancy Grand Cherokee, and that seems to do the trick). I feel nervous about them messing with the ML's electrical connections, or drilling into the dashboard to mount the brake controller. Any dealer recommendations for this? Any idea what it will run?

shortspark

I do not own a hitch because I don't tow anything but just yesterday I read an interesting article in the July/August issue of "Star" (the magazine of the MB Club of America). If you are a member look at page 64, the part with the title, "Trailering with an M-Class SUV". If you are not a member of the MB Club, I will give you some highlights from the article.

It says the ML is capable of towing 7200 lbs (6600 lbs if you have a 2wd). However, if you plan on towing more than 3500 lbs, you will need a trailer that has electronic brakes onboard and an electronic brake controller (EBC) in the tow vehicle. This box is installed under the dashboard within reach of the driver and is wired into the system of the car. According to the author, Rich Luhr, the rub is that very few dealers install these systems and they are not aware of the technical details to perform the install. If your dealer seems puzzled by your request to install this system run away as fast as you can and find an installer of hitches who knows what they are doing.

If your dealer is the only one available but still seems unsure of the protocol for installation, you can refer the service manager to this document which will show them step by step what to do and the proper sequence:

MB Star Bulletin T-B-31.19/07d

Depending on the model, an inexpensive MB pin kit may have to be added to the wiring harness to connect the ERC. There is still one other caution - the modern electronic control units in our cars and the modern LED lights on many new trailers "do not play well together". Luhr says that because these LED lights draw very little current, the car does not sense that there is a trailer plugged in so even if everything is wired up perfectly the system won't operate and you will have no trailer brakes. The work around is a special adapter cable (VW sells one for about ten dollars) or you can simply wire in a single incandescent running light with your trailer system and all will be well.

I have given you only the basic highlights to a most informative article and one that every ML owner who tows should read. I suggest you try to get a copy of this issue of "Star" (if you are a member of the MB Club you will be receiving it any day now in the mail).

MLee

I have just fitted the Prodigy wireless brake unit. The only mod to the ML is a 12 volt supply to the trailer plug.
I picked up power from the main battery cable from the right hand rear where the secondary battery is mounted. A relay triggered from the nearby power socket wiring ( cuts power if ignition off ) and a ciruit breaker, and job done. The controller just plugs into the power socket / cig lighter up front. Main operating unit screws to the trailer. This works great for me, as i have three vehicles to tow with. Just have to plug the controller into the vehicle i am using.

MLee.

Proteus7

Ack! The whole point of the RF I thought was to avoid any wiring? I had assumed that you just plug the wireless controller in the cig lighter up front, and the main unit attaches to the trailer in back, and plugs into both trailer brakes, and the 7 way connector next to the ML hitch?

Also..what is the largest trailer you're towing? I'm assuming I can do a light 26 ft (about 6k fully loaded, and 700 on the tongue with a wd hitch. The ml spec is for 575 tongue with no wd, but 1080 (in Canada) with?

MLee

No wiring would be great. BUT..... The electric brakes must get power from somewhere.....
If your trailer plug already has 12v power then no wiring is required. Mine had no power at the plug.
My camper is just 1200kg and I also tow a trailer that loads at about 2000kg
Here we are limited in some states to maximum tow weight not greater than loaded vehicle "gross" weight.

Mlee

Shrdlu

I had a dealer install a Tekonsha Primus IQ in the center stack cubby. Cost $600-plus, though. The MLs come from the factory with a connector for plugging in an aftermarket controller.

Everything else you would like to know about trailer brake controllers is in this thread:

https://mbworld.org/forums/new-m-cla...ng-diesel.html

frtdog

I know little about towed trailers but doesn't U-haul trailers use hydraulic brakes applied by some kind of sensor measuring the rate of deceleration of the trailer? If so if you are merely going to only occasionally use a trailer wouldn't that be the way to go thus avoiding the electronic brake controller?