Installing Trailer Brake Controllers

by Jim Hagerty

Model Selection

Electric trailer brake controllers alert a tow vehicle's brake system to operate a trailer's electric brakes. The installation process begins with choosing the best type of controller for a desired application. Generally, there are two types of electric trailer brake controllers. Proportional units provide the same amount of brake pressure to the trailer brakes as what is being applied to the tow vehicle. This happens simultaneously. With time delayed controllers, brake pressure is set by the user and trailer brakes function after a short delay.

Mounting the Controllers

Most controllers are installed on the firewall, out of the way of other vehicle components, or underneath the vehicle's dash. Some installation requires drilling into the firewall. Some units are installed using existing holes. While dash and firewall installation points are equally suitable, an area is usually chosen that will allow for simple wiring.


The trailer brake control unit draws power from the vehicle's battery with a circuit breaker and battery axillary. The unit is grounded to the chassis (commonly a black wire). The controllers communicate with the vehicle brake unit by a single wire (commonly blue). A separate connector (red wire) allows the brake lights to trailer brake lights operate. Wires are commonly routed along the floor of the tow vehicle or under interior trim. A removable harness connects brake controllers' wiring to the trailer's brake wiring system.

About the Author

Jim Hagerty is a writer and journalist who began writing professionally in 1996. He has had articles published in the "Rock River Times," "Builder's Journal" and various websites. He earned a Bachelor of Science in public relations and journalism from Northern Michigan University in Marquette.

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