How to Find the Brake Controller Port on a 2019 Thor Quantum KM24 w/ the Factory Tow Package

Updated 08/06/2025 | Published 05/22/2025

Question:

Hello. I have a 2019 Thor Quantum KM24 with the factory tow package. It’s a 2018 Mercedes Sprinter 3500XD Chassie per the vin . I am looking for a Brake Controller. I removed the front driver seat and no green 4 pin plug was found. It 100 has a factory tow package installed. Did they route the wiring behind the dash or somewhere else in the 2018 Sprinters? Any help is greatly appreciated. I want to order the correct brake controller from you all.

asked by: Bryan R

Expert Reply:

Hey Bryan. The brake controller port on the 2018 Mercedes Sprinter 3500 were only installed beneath the front driver's seat, like in the picture I attached below. If it was routed somewhere else you'd need to find the green 4-pin connector and follow it from there. Like you said this brake controller port was included with the factory tow package.

Are you the original owner? Could someone have already installed a brake controller and removed it but left the plug in adapter item # 3063-P? This is the correct one for your Sprinter 3500.

expert reply by: Jerred H

2018 Mercedes Sprinter 3500
(click to enlarge)

Bryan

8/5/2025

I am not the original owner, but my father inlaw is. He has not made any modifications. I understand the location of the green port is based on the Mercedes sprinter, but this is a RV. I’m assuming Mercedes doesn’t put an Axerra radio in their vans. The head unit is an Axxera with a rear camera. Since I can’t find the green port under the drivers seat, I’m wondering if Thor tapped into the wires (removing the green port) when they installed the Axxera head unit. It appears there are some wires being ran from under the drivers seat to the back of the radio. Sounds crazy, but this is what I’m seeing.

Jerred H.

8/6/2025

@Bryan Thanks for the information. That's not something we've encountered but sounds accurate. The brake controller plugs typically don't get moved. You can try to contact Thor Industries and see if they can tell you what they did with the connector. Another option is for you to follow the brake controller wire off of the 7-way and see where it leads you. It's in the 5 o'clock position as you're looking at the connector. If you lose it or it dead ends without a connector you can splice in some item # 10-1-1 wire and manually wire in a brake controller. What brake controller are you looking at?

Bryan

8/6/2025

@JerredH I actually did reach out to Thor after my earlier reply. The only info they had on file was “it’s the blue wire coiled under the dash”. I’ll check under the dash and report back. Thanks for your help.