Using a brake controller while towing a trailer involves setting up the controller, adjusting to the load size, adjusting braking sensitivity, manually activating the trailer brakes and possibly choosing a few personal settings.
In this guide we will unpack how a trailer brake controller works and the steps involved in how to use a brake controller while towing with trailer brakes.
How do electric trailer brakes work?
Electric trailer brakes are brakes built into the wheel assembly of a trailer. They use electromagnetic brake drums to help stop the trailer while towing, drawing power from the vehicle. As more power is applied, the electromagnets apply greater force.
Electric trailer brakes require an electrical connection to the tow vehicle. This allows for "programmable" brake operation. In order to tow a trailer with electric brakes, the tow vehicle needs to be equipped with a trailer brake controller.
What is a trailer brake controller?
A trailer brake controller is an electronic device that regulates the electric trailer brakes. It allows the driver to activate and monitor trailer brake activity from the cab of the vehicle.
A brake controller mounts in the cab of the vehicle and generally has a few different controls, such as an interface to view braking information and buttons to control the output and manual activation. Trailer brake controllers come in many different styles and capacities.
How Does a Trailer Brake Controller Work?
Time Delay vs Proportional
There are two basic types of brake controllers: time-delay and proportional or inertia-based. Each type is classified by the method of activation the brake controller uses.
Time-Delay Brake Controllers
A time-delay brake controller operates on very simple electrical principles. As soon as the driver presses the brake pedal, the time-based brake controller activates the trailer brakes, applying an increasing amount of power, fixed over time. This is called gain.
The gain setting of a time-delay brake controller can be adjusted by the driver to accommodate each specific trailer. However, the time-delay approach is not as precise as the proportional method.
Proportional Brake Controllers
A proportional brake controller or inertia-based brake controller uses an electrical circuit called an accelerometer to sense changes in momentum. When the driver presses the brake pedal, the brake controller applies power to the trailer brakes in proportion to the vehicle's momentum.
Proportional brake controllers provide smoother stops and more efficient braking. This is especially apparent when braking on a hill. If traveling up a hill, the brake controller applies less power, and if traveling down, it applies more power.
With your trailer coupled to your vehicle and your brake controller installed, the first step when towing with a brake controller is to make sure the trailer wiring harness is plugged into your vehicle. A brake controller requires power from the vehicle and a connection to the trailer brakes for proper towing.
During setup, make sure your vehicle and trailer are parked on a level surface. Also, make sure you are in a safe, open area with plenty of stopping distance and no other traffic around.
Step 2: Allow the Brake Controller to Calibrate
With the trailer plugged in, the brake controller may need to be calibrated. Most brake controllers are self-calibrating. Others do not require calibration at all.
Typically, self-calibrating brake controllers will flash a light or signal to indicate when the unit is calibrating and when calibration is complete.
Step 3: Select Personal Settings
Some brake controllers come with personal settings that can be adjusted to your preference, such as the angle of the interface, the brightness of the screen and even the location of the brake controller itself.
Be sure to adjust all of these settings before driving.
Step 4: Maximum Output - How to Adjust Trailer Brake Controller
Maximum output is the maximum amount of power the brake controller will apply to the trailer brakes. You will need to set this level and adjust it depending on the load size.
To adjust the output, press and hold the vehicle brake pedal. Adjust the output to the starting value specified in the instructions. Then, in an open area, test the trailer brakes by driving forward at about 25 mph and applying the brakes. If the vehicle stops too slowly, increase the maximum output. If it stops too abruptly or locks up, reduce the output.
Step 5: Adjust the Sensitivity Level
Sensitivity is how aggressively your brake controller will apply the brakes. You can set sensitivity by testing the trailer brakes again.
Drive forward at about 25 mph and press the brake pedal. If the vehicle stops too slowly, increase the sensitivity setting. If it stops too abruptly, lower the sensitivity. As operation becomes more comfortable, you can test braking at various speeds to ensure smooth stops in any conditions.
Step 6: Manually Activate the Trailer Brakes as Needed
Most trailer brake controllers come with a manual activation button. This allows you to activate the trailer brakes whenever desired, without applying the vehicle brakes.
Manual trailer brake activation can be useful for correcting minor trailer sway and gradually slowing down on a steep hill or before stops.
How to Use a Time-Delay Brake Controller Video
How to Use a Proportional Brake Controller Video
Do I Need a Trailer Brake Controller?
If you're asking yourself: Do electric trailer brakes work without a controller? The answer is, no. Electric trailer brakes do not work without a brake controller. If your trailer is equipped with electric brakes, you will need a brake controller to tow.
However, some trailers are equipped with surge brakes. These are a hydraulic braking system that uses the trailer's own weight and momentum to actuate the brakes. Unlike electric trailer brakes, they do not require a brake controller or even an electrical connection to the vehicle.
How to Adjust Trailer Brakes
Most trailer brakes are drum brakes and can be adjusted using a brake adjustment tool or even a flat screwdriver. Follow the trailer manufacturer's instructions. Most brakes use a "star wheel" adjuster and will require you to tighten the brakes until the wheel does not turn, then to back off slightly until the wheel turns freely.
Over time, you may need to replace the electromagnets or replace the brake shoes and drums. If you are not confident in your ability to inspect and adjust your brakes properly, you can take your trailer to a professional.
If you have a trailer shop adjust your brakes, have them lubricate your wheel bearings, check your wheel nuts and inspect your tires and valve stems at the same time.