While towing a trailer, you need extra power for both acceleration and deceleration. As proper acceleration is more about convenience, there are no regulations determining the minimum power of the tow vehicle. But proper braking is a safety concern, so heavy trailers (weighing more than 2,000-3,000lb, depends on the state) are equipped with their own brake systems, which one way or another assist the tow vehicle’s brakes. A trailer brake controller is a device informing the trailer's brake system about when and how it has to operate.
Depending on your tow vehicle’s equipment, you may have a factory-installed controller or need to add one yourself. With the towing package available, all you need to do is connect the trailer’s pin to your truck’s socket and set the necessary braking effort, which you determine during a test drive described below.
Without the standard controller, you have two alternatives yet again depending on your vehicle’s equipment. In case it has a 7-pin connector in the rear, it also almost certainly has the trailer brake service connector typically located beneath the steering column. With this connector, you can add and remove the controller without any modifications. If the tow vehicle doesn’t have such a connector, then you need to do all wiring yourself and only then install the controller.
Calibration of the brake controller is important, because varying weights and road conditions require different setup from the system. Too much of the braking force results in wheel lockup, which is highly dangerous and bad for tires. Insufficient effort provides weak assistance, overloading the tow vehicle’s brakes and increasing the stopping distance.
To calibrate the trailer brake controller, take your vehicle with a trailer to a flat and dry paved area. You have to accelerate it up to 20-30 mph and release the throttle pedal. Move the manual control slider on the device all the way to the maximum limit. Having noticed the lock-up of the trailer wheels, switch down to the next setting using the “-” button (lever or roller). Repeat the ride and adjustments as many times as necessary until the wheels no longer lock. Your aim is perceptible deceleration occurring without the vehicle’s own brakes applied. Use the “+” button to switch up the setting in case braking power is insufficient.
Generally, most car and custom brake controller manufacturers provide instructions describing all the necessary procedures for the given device, so try searching on the internet by your vehicle’s make and model (if you have a standard controller) or use the brand and code/name of the device for a more accurate description.