How to Wire Trailer Brakes

It is important to have functioning brakes on the trailer when you are towing a car or recreational vehicle. Some trailers rely on the tow vehicle's brakes to stop, whereas other trailers have their own brake systems. These controllers supply power from the tow vehicle to the trailer's brake system. This article will tell you how to wire trailer brakes.


  1. 1
    Find the cold side of the "stoplight" switch by probing the terminals until one is lit when the brake pedal is depressed. Mark the cold wire.
    • The "stoplight" switch is located on the brake pedal and activates the brake lights.
  2. 2
    Disconnect the negative battery cable of the tow vehicle. Install a 2 0amp auto-reset circuit breaker as close as possible to the positive battery terminal.
  3. 3
    Use ring terminal connectors to connect the "BATT" side of the breaker to the terminal.
  4. 4
    String through one black and one white wire from the brake pedal to the tow vehicle's battery.
  5. 5
    Connect the black wire to the "AUX" side of the circuit breaker with a ring terminal and connect the white wire to the negative battery cable with another ring terminal.
  6. 6
    Attach the brake controller's black "battery" wire to the black wire on the "AUX" side of the circuit breaker with a butt connector.
  7. 7
    Attach the controller's white "ground" wire to the white wire from the negative battery terminal.
  8. 8
    Splice the red "stoplight" wire to the cold wire determined in step 1 using wire strippers and the wiretap provided with your controller.
  9. 9
    Attach the brake control's blue wire to the trailer's blue brake wire. Secure loose wires with cable ties so they will not be damaged in transit.
  10. 10
    Consult your vehicle's manual for special instructions on reconnecting the battery for towing.


  • Some vehicles have factory trailer towing already equipped on them. Consult your owner's manual for wiring directions for these cars.
  • The U.S. Department of Transportation requires that all trailers with their own brake systems have a trailer breakaway system installed. Consult your trailer manufacturer for more details.


  • Do not connect the black "battery" wire to the fuse panel or car accessory wiring. This can also damage wiring and cause brake failure.
  • Some electronic brake systems are only compatible with 12 volt negative ground systems. Check your vehicle manual before installation.
  • Do not reverse the black and white wire connections. Brake control failure can result.

Things You'll Need

  • Probe circuit tester
  • 20amp auto-reset circuit breaker
  • Wire strippers
  • Various ring terminal and butt connectors
  • Wire crimp tool
  • Cable ties

Article Info

Categories: Cabling and Wiring Connection