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Trailer Brake Controller

 
Old 12-28-2013, 07:44 AM
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Trailer Brake Controller

I am getting ready to order an ML 350BlueTEC with the factory installed Hitch Kit option. The website says that the car will have the wiring harnesses for the trailer lights and brakes.

Does this mean that there will be a plug connector hidden somewhere to connect a Trailer Brake Controller? If yes, where is it located? This connector plug is standard on most new vehicles sold with a factory hitch in the US. On my 2010 Audi Q7, it was hidden behind the dash above the driver's feet.

When I asked this question of a salesman at one dealer, he called a tech who told him that it was 2 hrs labor to wire the trailer brake controller. If there's a connector plug present, it shouldn't take that long; but maybe that's the MB Flat Rate Manual charge. I would much prefer to install it myself.
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Old 12-28-2013, 12:18 PM
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The connector for an aftermarket trailer brake controller--MB doesn't offer one-- is under the driver's side floormat. It is the standard four-wire receptacle.

Everything else you would like to know about TBCs is in this thread:

https://mbworld.org/forums/new-m-cla...ng-diesel.html
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Old 12-28-2013, 12:41 PM
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Originally Posted by Shrdlu View Post
The connector for an aftermarket trailer brake controller--MB doesn't offer one-- is under the driver's side floormat. It is the standard four-wire receptacle.
Thanks I figured as much. It's obviously something I can do myself, as I did with my Audi Q7. So much for dealer salesman's knowledge and dealer tech's flat rate labor (2 hrs) attitude.

Aren't these forums great!

Another question. Is the electrical plug back at the hitch a standard 7-pin RV receptacle?

Last edited by DUTCH; 12-28-2013 at 12:52 PM.
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Old 12-28-2013, 02:17 PM
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Yes, it's the standard 7-pin receptacle as found on American RVs and pickups. All you need is a controller and you're good to go.
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Old 12-28-2013, 02:33 PM
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Originally Posted by Shrdlu View Post
Yes, it's the standard 7-pin receptacle as found on American RVs and pickups. All you need is a controller and you're good to go.
Viel Dank!
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Old 12-30-2013, 04:38 AM
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ML350 BT soon......pleeeease. GOT IT NOW....Wooooo
I have one trailer and multiple cars so i fitted a Teckonsha wireless controller.
The unit bolts to the trailer and the little controller just plugs into the cig lighter socket. This means i just swap the controller to each vehicle as needed.....plug and play.
The only difference to wiring plug is the brake pin requires 12volts. I just fitted a bridging wire from the aux. terminal...... All good.

Mlee
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Old 01-04-2014, 08:20 AM
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I added the Teckonsha P3 to my ML. The connector was easy to find under the carpet drivers side. I followed the T-B-31.19/07c star bulletin that I found online, even though it's a few years old. It was exactly the same. Ordered the connector housing (A039 545 35 28) and the required pins that go inside the connector that the wires connect to (A046 545 40 28) and (A035 545 74 28). Ordered the parts online and let them ship it to me so I did not even need to visit my dealer, and the total cost was less than $30 as I recall. No one makes the correct harness for our application that I could find.

Since I only tow the trailer that has brakes a few times a year, I did not make a permanent install, but put the unit in the dash cubby just above the cup holders. I've used it once and everything worked fine.
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Old 01-04-2014, 08:30 AM
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Originally Posted by Kartergreg View Post
I added the Teckonsha P3 to my ML. The connector was easy to find under the carpet drivers side. I followed the T-B-31.19/07c star bulletin that I found online, even though it's a few years old. It was exactly the same. Ordered the connector housing (A039 545 35 28) and the required pins that go inside the connector that the wires connect to (A046 545 40 28) and (A035 545 74 28). Ordered the parts online and let them ship it to me so I did not even need to visit my dealer, and the total cost was less than $30 as I recall. No one makes the correct harness for our application that I could find.

Since I only tow the trailer that has brakes a few times a year, I did not make a permanent install, but put the unit in the dash cubby just above the cup holders. I've used it once and everything worked fine.
Good info. Thanks.
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