How Do Trailer Brake Controllers Work

Updated 03/14/2019 | Published 03/13/2019

Question:

Not clear how a brake controller works. Is it binary as in on or off? If not how does the brake lights on the trailer using the same line work? Also if a brake controller black main power line is not working due to fuse, would the brake controller still light up its light from the red brake line signal? Hard to find and real info on how these things work...

asked by: Joe G

Helpful Expert Reply:

An electric trailer brake controller is a device that installs in the cab of your tow vehicle and activates your trailer's electric or electric-over-hydraulic brakes when you hit the brakes in your tow vehicle. It's not a binary activation. There are two main types of controllers out there.

A proportional brake controller senses how the tow vehicle is slowing or stopping and applies the trailer's brakes with the same intensity. So if you slam on the brakes in your tow vehicle, the controller will activate your trailer's brakes just as forcefully. With a proportional controller, you can adjust the initial braking power and aggressiveness based on your trailer's weight and your braking preferences.

A time-delayed brake controller activates the trailer's brakes with a preset intensity (power output) and rate of application (sync), both of which are determined by you. With this type of controller, there is a delay between the time that you initially apply the brakes in your tow vehicle and the time that the controller reaches maximum power output to the trailer's brakes. However, this delay can be adjusted with the sync setting.

With a proportional brake controller, you can get heavy-duty emergency braking, general braking, or slow-to-an-idle braking for your trailer automatically. The intensity with which your trailer brakes are activated and the rate at which they are applied are dependent on the deceleration of your tow vehicle. This means that, unlike time-delay controllers - which send the same amount of preset power to your trailer brakes every time - proportional controllers are able to adapt to every braking situation differently. So if you slam on the brakes in your truck, your trailer brakes will activate with the same extreme intensity. And if you merely slow down as you approach a red light, your trailer will gradually brake in the same manner.

A proportional brake controller senses when and how your tow vehicle brakes by means of an accelerometer or an internal inertia-based sensor. The accelerometer or sensor responds to the deceleration of your tow vehicle as you brake by signaling the controller to send out enough power to your trailer brakes so that they are activated with an intensity that matches. The result is uniform braking across your towing setup. No push-pull action - just smooth, proportional braking every time. That's why we recommend them the highest like our best selling P3 # 90195 that has the most advanced inertia sensor, and is the most reliable and easy to understand.

expert reply by: Jameson C