Brake Controller installation

Shinohara

Member
Hi all, I've already installed an aftermarket hitch and 4-pin trailer lights connector in my 2016 CX-9 GT and am now looking at adding a brake controller and 7-pin connector so I can more safely tow a tent trailer or other lightweight camper. Does anyone have experience with this? From the research I've done it looks like it will involve running brake and power wiring under the vehicle from the hitch, up to the engine compartment, and then running the brake signal and a second power connection through the firewall to the controller. Is this correct? Has anyone done this install themselves and if so any tips on where to secure/route the wiring under the vehicle. Is there any existing wiring in the factory loom and trailer connector that make this simpler?
 
I installed a brake controller and tow a pop up.
Its been a while since I installed it, so I am not sure which cables ran to what, I just followed the instructions which came with the brake controller.

I do remember where I ran the cables though: I started in the rear at the connector and ran them in the bumper above the exhaust to the drivers side trunk. There is a rubber grommet through which I pulled the cables. From there I ran them under the trim on the drivers side next to the third row seats and attached them to the existing cables running towards the front of the car under the door sills. My brake controller is attached to the trim under the steering wheel, the power cables run through the firewall where all other cables are too. There are two soft spots in the rubber grommet (towards the perimeter of the grommet) where I pushed the cables through, they come out behind the battery in the engine compartment. I installed the circuit breaker which came with the controller under the flappy rubber trim on the drivers side of the engine bay. There are a few struts which hold the fender in place which lent them selfs perfectly for attaching the circuit breakers without drilling into the body panels of the car with the self tapping screws. From there its off to the battery.

I had no idea how to do any of this, so in all it took me about 9 hours. I did not want to run cable under the car if I could help it as I wanted as little exposure to the elements as possible.

I tapped into the brake switch at the pedal which is sub optimal as the trailer brakes only come on when I press the pedal, not when the car applies the brakes using cruise control. At some point I will tap into the brake light cable and change it.

Let me know if you have any questions and I will try and help.
 
7-pin trailer wiring connector:
1--negative
2--trailer brakes
3--tail lights
4--12 volt battery charging line
5--left turn & stop lights
6--right turn & stop lights
7--optional back up light

Suggestions---Use wire of ample gauge size. One gauge bigger than usual can't hurt, and also gives more physical strength. #12 for the negative and battery charge line is good. #14 for the brake power. Never use wire nuts on anything as important as the brake positive & negative wiring; properly installed crimp connectors are OK, and soldered and heat shrink tubing are best. Run the negative line all the way to the battery negative post. Don't trust a chassis connection--your brakes depend on good connections.

7-Way-RV-Style-Trailer-Plug-Wiring-Diagram-1.png
 
How did you run through the firewall? I*m working on my install and it seems like there*s 2 firewalls, and all the cabling is routed through a very snug rubber hose assembly into the engine bay.
 
How did you run through the firewall? I*m working on my install and it seems like there*s 2 firewalls, and all the cabling is routed through a very snug rubber hose assembly into the engine bay.



I ran it through one of the "holes" which look like nipples from the engine side... <blockquote class="imgur-embed-pub" lang="en" data-id="a/IXuBt6y"><a href="//imgur.com/a/IXuBt6y"></a></blockquote><script async src="//s.imgur.com/min/embed.js" charset="utf-8"></script>

A clothes hanger with lots of soapy dish water helped me pull it through.
 
I eventually figured out how it was assembled. I got all my wires pulled last night and hooked power up to the trailer connector. Going to finish wiring power and ground to the brake controller tonight, install the controller, and hook in to the brake switch. That last part looks excitingly difficult to reach.
 
I am seriously considering running a wire from the break light wire to the controller. The brake controller does not activate when on cruise control and applying the brakes as the brake switch never gets toggled.
 
I know it*s probably in that massive wire loom going through the firewall, but I*m not crazy enough to try and find it. I*ll stick to manually braking when I*m towing.
 
I ran it through one of the "holes" which look like nipples from the engine side... <blockquote class="imgur-embed-pub" lang="en" data-id="a/IXuBt6y"><a href="//imgur.com/a/IXuBt6y"></a></blockquote><script async src="//s.imgur.com/min/embed.js" charset="utf-8"></script>

A clothes hanger with lots of soapy dish water helped me pull it through.

OK, I'm at this step of the process. That's a great picture. I can see it from the interior, but can't see it from the engine bay. What's the best way to access this area?
 
I finally finished my brake controller installation. Like Midnight Rider, I brought the wires from the 7-pin connector through a grommet in the spare tire well, routed it under the door sill trim, and through the firewall. To more easily get through the large rubber firewall grommet, I enlarged the hole at the nipple on the engine compartment side of the grommet using a Dremel tool and a grinder. The circuit breakers were installed under the hood next to the rubber trim as Midnight Rider described.

The Redarc Tow-Pro Elite controller was mounted on an empty bracket I found under the dash. The controller was mounted with nuts and bolts, Scotch mounting tape, and a zip tie. Overkill - but I'm confident that thing won't be moving.

48634436242_8b5da3ea97_z.jpg


On the right you can see the brake switch. I identified the wire which only has power when the brakes are applied via the brake pedal, and tapped into it with a splice connector.

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As others have commented, the trailer brakes will be activated by the brake pedal but not when the brakes are activated by the cruise control.

I chose the Redarc brake controller because the only part of the controller that is visible inside the car is an inconspicuous knob. I installed it below the switches on the left side of the dash. I had to modify the back side of the dash panel a bit for the controller's switch module to fit.

48636278908_1a3bddeb65_z.jpg


A press on the Redarc control knob will apply the manual override brake to the trailer. The knob is easy to see and reach and doesn't affect leg room like many other brake controllers on the market.

My CX-9 is trailer ready!
 
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How would it be if you connected the controller's brake sensing wire to a brake light power wire instead of the brake pedal switch?
 
How would it be if you connected the controller's brake sensing wire to a brake light power wire instead of the brake pedal switch?

Seems like it would work. The last part of the instructions for the Redarc unit I installed mentioned it:


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