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Old 04-18-2013, 06:34 PM   #9
Join Date: Aug 2010
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Default Re: Tapping into MB factory installed aux battery

Yes I do have the factory harness. I have a swivel seat base and have had the seat off previously so i know what you mean, it's a bit of a bear. I ordered the connector and pins today, they'll be in tomorrow. I also have a Tekonsha P3 on the way.

I'll be putting in a battery monitor also (brand/model to be determined) which will require me to get the seat off so i'll tackle a few items at once.

Originally Posted by sailquik View Post
Does your 2010 144" wb Sprinter have the factory installed trailer towing package?
If so, no need to remove the drivers seat (I did that once....not doing it again unless absolutely necessary)
to install your trailer electronic brake controller.
Pull the plastic cover off (where you have access to all the fuses under the driver seat) on the LH side of the
drivers seat box and take a flashlight and look around on the bottom of the seat box area.
You will find a light green 4 pin connector that is already attached to the trailer wiring adapter on the top
middle rail of the under the seat electronics package.
Do search on "green connector" for a lot more ...everything you need.
You will have to buy the mating connector + 4 pins from a Mercedes Sprinter dealer, but it's a very straight
forward task once you have the parts and have located the factory installed connector.
The part numbers for the mating green connector and 2 sets of pins (one larger AWG than
the other) are:
Connector: 039-545-35-38 (my cost $2.24)
4 Pins: 046-545-40-28 (my cost $2.59 ea=$10.36)
4 Pins: 035-545-74-28 (my cost $2.41 ea= 9.64)
If you have any trouble getting these parts, let me know and I can give you a POC at
Sun Motor Cars Mercedes in Mechanicsburg, PA that can order them for you.

If you don't have the factory installed trailer wiring harness....good luck.
I'd suggest having a dealer install the complete harness to avoid many issues.
Check out this link:

Last edited by Legwound; 04-18-2013 at 06:44 PM.
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