Trailer Brake Controller Install 2018 Mazda CX-9 Grand Touring

Updated 08/26/2019 | Published 08/25/2019

Products Featured in This Question

Pollak Heavy-Duty, 7-Pole, Round Pin Trailer Wiring Socket - Vehicle End

(154)

$13.86

Universal Installation Kit for Trailer Brake Controller - 7-Way RV and 4-Way Flat - 10 Gauge Wires

(3448)

$124.19

Hook Probe Circuit Tester

(66)

$12.94

Question:

I need to connect the red wire from my Redarc Tow-Pro Brake Controller to my 2018 Mazda CX-9. Your ETBC7 instructions say the red wire must be spliced into the cold wire at the brake switch. Ive located the switch picture attached, which has 4 small gauge wires, red, blue, black, and green. Its difficult to reach, and so far I havent been able to unplug the wires from the switch. 1. Im unclear on how to test the wires to identify the cold one. Do you know from the colors which one it is? 2. Im assuming the blue wire splice from the ETBC7 is for 16-14 gauge wire, which will work for the brake controllers red wire. The wire on the switch looks like it may be 18 gauge wire. Will the blue splice connector work with such a small wire? 3. The Redarc instructions say the brake light terminal on some vehicles may provide a suitable connection for the red wire, but not necessarily for all vehicles. Do you know if the brake light terminal is a suitable option for my Mazda CX-9? Thank you.

asked by: Mark

Expert Reply:

Since you've got a few questions in here, in order to make sure everything is addressed clearly I'm going to list the answers to each of your numbered questions below.

1) You can test the wires using a Circuit Tester kit like # PTW2993 to determine which is the cold wire. Since auto manufacturers don't have a standard color they all use, it's tough to determine what is what on some manufacturers. The only way to truly know which wire is which on your vehicle is to test for power when the brake isn't pressed and when it is.

2) Joining 2 different gauge wires is not uncommon, especially on automobiles. The # ETBC7 uses 10 gauge wires, but you still should be able to connect it to the smaller gauge wire. You'd probably be best served to twist the 2 together to join them and then finish with electrical tape, but you may be able to use a butt connector. To use a butt connector, fold the smaller gauge wire over itself and insert it into one end of the butt connector; then insert the larger gauge wire into the other end and crimp both ends.

3) RedArc recommends checking with the vehicle manufacturer; usually if we've done an install on a specific vehicle we can tell you with certainty if the connection is going to be suitable for this application or not. Unfortunately we have not done an install with this specific brake controller on this vehicle, but I recommend tapping into the stop light switch like you're already looking to do. You should be able to do it this way without any issue.

expert reply by: Erik B