[CarBizIndio]

Has any one ever installed a factory tow package? I'm curious how Mercedes handles the wiring and how their brake controller works for example is is adjustable?

Any tips would be much appreciated.

 

[lkchris]

The factory tow package does not include any wiring for a brake controller and there is no Mercedes brake controller.

The dealer installation will get you a hitch and a trailer plug that will run your lights.

There is a factory wiring harness for a brake controller to run from the right rear to the left front of your vehicle and installation of this harness by itself is a massive job. The harness part number is 164 540 69 13 (something your dealer might not know) and it may require some modification to work. Get a Tekhonsha or Curt, etc., brake controller from a trailer supply store and connect it to this wiring.

 

[mc6gainRamp]

I recently installed a factory hitch and (non-brake controller) wiring harness in my 2009 GL320. Although it took some time to figure out, the hitch and wiring were relatively easy to install. The dealer I purchased the hitch and harness from was gracious enough to print out the installation instructions for me.

After installation, I took it to the dealer for the required SAM and gateway programming, after which I had a fully functional hitch and (non-brake controller) wiring setup and a fresh car wash.

There is a wiring harness for trailer brake controllers that runs from the SAM in the left rear to the driver-side under the dashboard. This is a major installation since it requires removing the seats and flooring to get access to the factory wiring channels. Even if you run the brake controller harness, there is not a good location to mount a controller box due to the location of the driver-side knee airbags. I've seen some pictures of trailer brake controllers mounted on the top of the dashboard. The trailer brake controller harness has a hefty price tag for a dealer installation because lots of the interior needs to be disassembled to access the wiring channels.

As an alternative, there are wireless brake controllers that you can install with a lot less effort than installing the factory brake control wiring harness. These will have a box that installs in the same place as you would mount a controller with the factory brake controller harness, but it communicates wirelessly to the trailer via a dongle that plugs in-between the tow vehicle and the trailer.

Disclosure: I have not installed a wireless brake controller, my above answer is based only on research I have done on the topic.

 

[Ryan Kubla]

Bringing this thread back to life.


Does anyone know exactly where the trailer wire harness plugs in at? Does it plug in the back of the rear fuse box or somewhere else?

Thanks

 

[GLJack]

To harness plugs into the rear Sam in the right rear of the vehicle.

 

[Ryan Kubla]

Just looked at the sam unit, it has a open spot but it's a different plug than the trailer plug. Do I need a different sam unit?

 

[Ryan Kubla]

I can take a picture if it'll help.

 

[GLJack]

Do you have the factory harness

 

[GLJack]

Your Sam unit should have 9 places in it. What year Gl is this.

 

[mc6gainRamp]

If I can presume from your question, you are planning on installing the factory tow hitch and factory wiring harness? The upgraded SAM is only compatible with the factory wiring harness which is only compatible with the factory tow hitch.

GLJack's suggestion on the number of sockets is a good indicator, else you could also call your local dealer with the VIN and they would be able to tell you which SAM was installed.

In my research, the general rule of thumb is that 2009 and newer GL's have the upgraded SAM and 2008 and earlier vehicles would have needed an option package such as the towing package or the side vent windows to have the upgraded SAM.

In my 2009 GL, the factory wiring harness plugged into the SAM socket closest to the right rear corner of the vehicle although I couldn't get a good look at it since it was buried underneath the Harmon Kardon sub.

 

[GLJack]

My haven't seen the sam on my 07. Has Wing windows, do you think some came without power wing windows. Putting hitch on mine soon.

 

[GLJack]

Thanks for that piece of info Mc6gainRamp, I see my 07 has option (848 side window, electrical hinged.)Was looking at getting a used factory hitch, harness and Sam from a Gl450 but If the price comes in to high I may pass on the sam.