Trailer brake controller concerns (2018 CX-9)

barter

Member
Hi,

I have a cx-9 signature 2018. I want to install a brake controller for my pop up trailer with electric brakes.
All brake controller instructions I found are telling us to wire to brake pedal signal.

I think it's not suitable for this car since it would not pickup brake signal when cruise control is automatically braking the car. Same issue with automatic emergency brake system.

This could result in trailer jack knife if car is automatically breaking hard and trailer brakes are not applied.

I found suggestion about tapping the center brake light signal instead of brake pedal signal. Anyone know how to Hook to the center brake light signal from the dash area? I don't want to run a wire back from tail gate to brake controller for this purpose.

Thanks.

FranK.
 
I have no experience with this, but if you are looking into wiring to the center brake light, why not wire it to your hitch wiring harness brake light signal?

Edit: Didn’t see you were asking about wiring from the dash area.
 
:
2016 CX-9 GT
I have no experience with this, but if you are looking into wiring to the center brake light, why not wire it to your hitch wiring harness brake light signal?

Edit: Didn’t see you were asking about wiring from the dash area.
Do you know which wire from the hitch wiring is the stop light on the Mazda side of the harness?
 
Good on you for wanting to tow properly. Will you be adding a 7 pin connection or already have one? Or is this a wireless trailer brake controller?

Edit: To strictly answer your question, I do not know where to grab the brake light signal up front. Sounds like some time studying wiring diagrams or tracing wires is in order.
 
Do you know which wire from the hitch wiring is the stop light on the Mazda side of the harness?
Not exactly, but you can check the wiring harness installations videos for the cx-9 on Etrailer.com
I saw one that taps into the rear brake light but there also others that show how to connect into the OEM tow wire harness connector.

The 4 pin trailer harness end is no good for brake booster use because it combines the turn signals and brake signals, but it looks like the OEM tow wire harness connector before that is an 8 pin and would most likely have a dedicated brake signal wire. (Tbc). The OEM tow wire harness connector is in the cargo area on the passenger side. The etrailer videos explains well how to access it.

edit: the support team at etrailer.com would probably be able to give you the answers you need on where to connect the brake booster as well.
 
:
2016 CX-9 GT
Thank you, I will have to look into those videos.
I connected mine on a brake pedal wire, as when I was installing it that is what my directions said. Unfortunately the trailer brakes do not actuate when the car brakes using cruise control, only when I step on the brake pedal.