EDITED as of 27/01/2020
So it’s been a while since I have updated the site as I have been building a custom off road camper as you can read all about here.
Now that I am installing electronic brakes on the camper, I needed to install myself a brake control unit. Now, there are plenty on the market and I’m not the person to give you any recommendations on which one is better. I will tell you I went with the Hayman Reese CompactIQ® Brake Controller.
What I will tell you is how I installed it which may save you some time should you decide to install one yourself. Please note that all electrical work should be completed by someone who knows what they are doing and I take no responsibility for any damage you may cause by attempting the installation. Now that that’s out of the way, lets get down to business.
This particular brake controller unit only required four wires to be installed.
Power (Positive and negative – not Ground), brake input and brake output to trailer plug.
Lets start with Installation location. I installed the control unit under the start button, there is a nice space there and also that’s where I wanted to install my brake controller adjustment (I have run out of blanks so I used the space beside).
I made a small right angle bracket and mounted the brake controller in the position detailed in the fitting instructions.
I then ran two wires, through the firewall located directly behind the same location into the engine bay and over to the battery. I placed a 20amp fuse on the positive wire and and attached the wires to their respective terminals.
Two wires down, two to go.
Now the instruction tells you to tap the brake pedal switch which for me was not as easy as it sounds (there are some wiring harness that have piggy back plugs however mine did not). I decided to connect mine to the tail light wire which activates when you press the brake pedal.
This needs to be tapped on the other side of the tow ECU which should be located in the jack access panel as per Graham’s comment below.
I belled out the brake wire coming from the tow ECU and tapped that wire. I then ran the tap all the way back to my brake controller.
I’m about to save you about an hours worth of work right here. Now you could run a wire from the control unit all the way to the brake light, or you could just use the brake light wire I traced all the way from the tail light to the passenger kick panel which makes this install so much easier.
Remove the passenger protection strip and then the kick panel.
Once removed you need to locate the (Blue and orange) wire and (Blue) wire.
(Photo removed)
In this picture (above) this is the blue and orange wire. This is the brake light wire.
You should always test this for yourself in case this has changed with the later models. Simply use a multi-meter or test light which should activate when the brake pedal is pressed.
In the picture below, this is the blue wire. This is the brake wire that goes to the trailer plug (assuming you already have a tow kit installed otherwise why would you be installing a brake control unit.)
I then tapped into these two wires and ran them across to the driver side behind the dash and connected them up to the brake control unit.
I am not a fan of quick taps or scotch locks so I soldered directly to the wires.
With everything connected, it was time to test. I hooked a multi-meter to the trailer plug and measured the voltage when I manually activated the brake controller by pressing the button. All good, I had voltage coming through and everything appears to be working.
I did notice as soon as I pushed the brake controller button I got an alert on the dash saying the FCM was unavailable????? It took me about 30 min to work out what was going on. The vehicle computer was disconnecting the FCM as the break line was having power drawn from it without the brake pedal being pressed so the computer was thinking there was an error.
As soon as I pressed the brake pedal and then manually activated the trailer brakes the error was not thrown up.
This issue does not occur now that that the brake light is tapped after the tow harness ECU.
I am not sure when you would manually activate the trailer brakes without the brake pedal pressed because this is the whole reason to install the brake controller so it is automatic, never the less I’m sure there is a reason for it, (I just used it for testing everything works.
Here is the explanation for the manual override brake from Graham.
“manual over ride is very commonly used when towing vans. It is useful on long descents for an additional ‘touch’ and very useful to control trailer sway by ‘stretching’ the rig from the rear…instantly stops sway. You need manual over ride.” Thanks Graham!
If I have missed anything or you would like more info, please let me know. Happy 4WDing!
The Pajero Sport 
Hi there, I installed a similar unit in my Paj Sport 2 yrs ago.
You should be aware that the Paj Sport and all modern vehicles are equipped with CAN bus (look it up if not familiar) for digital comms between the various ‘smart’ devices on the vehicle like Electronic Stability Control and Automatic Collision Avoidance – both of which use electronics via the CAN bus to activate the vehicle brakes under certain conditions determined by G sensors and other sensors assessing current dynamic conditions.
Just ‘tapping in’ to pick up the brake light wire as you describe it is potentially quite dangerous. While the signal to the brake light will definitely operate the trailer brake controller normally, it is the manual over ride which creates the danger. And that is the purpose of the alarm that you are seeing. Do not ignore.
When the manual over ride lever is operated, 12 volts is inserted onto the brake light wire, which to the vehicle’s standard set up, means the driver has foot on brakes which is a false signal to the ESC and other brake related systems.
For non qualified installers, in my view, the only safe way to do this install is to either obtain the Mitsi spare part (around $100) that is designed to correctly connect the brake controller to the vehicle’s harness or, connect the brake light sense wire for the controller in a part of the vehicle isolated from the CANbus.
In my case, I picked up the brake light wire on the trailer side of the repeater unit installed in the jack/tools compartment at the left of the rear load area as part of the tow bar install. This has worked perfectly and is completely isolated from the CANbus digital environment.
And by the way, manual over ride is very commonly used when towing vans. It is useful on long descents for an additional ‘touch’ and very useful to control trailer sway by ‘stretching’ the rig from the rear…instantly stops sway. You need manual over ride.
All the best and thanks for a useful site.
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Graham, you are 100% correct. Yeah im all over CAN bus and figure that is what was happening.
I will take your advice and correct the brake wire and tap the other side of the tow harness which I have previously installed and update the post as you make a very good correction.
Also your explanation of the manual activation makes sense. Ive only towed smaller low weight trailers and have never come across that issue.
Ill have the post corrected within a few days.
Thank you fkr taking the time to write your comment.
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obtain the Mitsi spare part (around $100) that is designed to correctly connect the brake controller to the vehicle’s harness or, connect the brake light sense wire for the controller in a part of the vehicle isolated from the CANbus……unquote!
Resubmitting these questions…due to accidentally deleting them earlier.
1 what is the spare part your referring to?
2 how did you find the brake light wire at the jack area where there are several harnesses, an ECU and various connecting plugs?
Item 2 would be my preference for connection as I don’t believe there is enough room for another harness back to front of vehicle under the trims? However unable to find the brake light wire due to reason mentioned in 2. Any help would be greatly appreciated!
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Graham re your comments Jan 23rd what is the$100 mitsubi part your referring to?
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I picked up the brake light wire on the trailer side of the repeater unit installed in the jack/tools compartment at the left of the rear load area as part of the tow bar install ……….
How did you identify this wire down at the jack tools area where there are numerous harnesses , the ecu and various quick/smart connect plugs
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Well I’m glad i found this write up. I was planning on wiring up the same controller on the same vehicle. I was planning on wiring it up in the same way you explain but now that I’ve read your write up I am confident that I am going about it the right way.
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Did you use a premade wire harness? Or if you did it youself, did you buy a plug to match the Compact IQ or did you just cut the plug off the controller and make your own connections.
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Hmm it was quite some time ago, but I would have no doubt made my own connectors.
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