How to Do: Brake Controller Installation

A brake controller is a device that is mounted on a tow vehicle in order to achieve a better braking efficiency. When a tow vehicle brakes, it is important that the trailer behind it engages a similar action. This action is realized through the use of electric trailer brakes, and the installation of a brake controller that would guarantee their operation. Electric trailer brakes use the action of a pulling magnetic piston when energized for them to brake. These brakes are connected to the controller which is in turn connected to the braking system of the tow vehicle.

The two main types of brake controllers are proportional and time-delay. Proportional brake controllers are more expensive and complex to install, qualities opposite to their time-delay counterparts. Therefore, time-delay controllers are more convenient. These controllers incorporate a delay between the times when the brake pedal of the tow vehicle is pressed to when the trailer brakes are engaged. The delay is adjustable to suit the driver's preference, a load of the trailer, and the terrain being driven on.

Both proportional and time-delay controllers are designed with a button or slider that acts as a manual override in case of an emergency.


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1. Mounting of the Brake Controller

The brake controller must be mounted in a position that is easily accessible to the driver. The mounting angle and direction should ensure this is achieved. The tow vehicle driver should be in a position to comfortably read the controller digital display as well as reach all its controls. This is important in a case of an emergency where the use of the manual override is required.

The mounting surface should be rigid enough to cancel out an excessive vibration of the controller. The surface onto which the controller is mounted should be carefully assessed to ensure it is solid. The nature of the surface will dictate the performance of the controller because, for a greater degree of vibration, the performance of the device becomes poor. The preferred position is usually under the tow vehicle's dash. The mounting bracket is tightly screwed into place using self-tapping screws that are just long enough to avoid any damage to wires or components under the dash. The controller is then anchored onto the bracket through the manufacturer provided screw holes on it.

2. Wiring of the Brake Controller

Care should be taken to ensure all the brake controller wires are connected properly for it to operate correctly. Improper connection and wiring of the device may lead to the loss of the trailer braking, as well as the destruction of the device.

The controllers usually come with four wires which perform different functions and connect to different points. These wires are color coded red, blue, black and white.

Brake Controller Installation

White Wire – the white wire provides the required grounding to the device. This wire should always be connected first to reduce any risk of injury or damage to property. It should be connected to the best-known grounding point on the towing vehicle. This is achieved through the direct connection to the negative post of the tow vehicle battery, or a grounded metal part of the firewall. However, it is preferable to connect the wire to the car battery's negative terminal.

If the white wire is wrongly connected, therefore improper grounding, it will result to poor or no performance of the controller. This connection can also lead to the destruction of the device.

Black Wire – this wire should be the second connection made during the installation. The black wire provides a positive connection to the power system of the tow vehicle, therefore, it is directly connected to the positive post of the vehicle battery. The wire should not be connected to the power supply line of the tow vehicle or the fuse panel as this may lead to circuit overload or damages to other electronics in the vehicle. A self-resetting circuit breaker must be connected in-line between the controller and the battery.

The choice of the circuit breaker is influenced by the number of brake light bulbs in use, for both the tow vehicle plus the trailer, as well as the number of trailer brakes. The higher the number of bulbs and trailer brakes, the higher the rating on the circuit breaker to be selected.

The black wire should be routed through the firewall grommet hole in order to prevent it from grounding. It should also follow a path that is away from that of the radio antenna as it may cause AM interference.

If in any case, the vehicle does not have an already existing grommet, a hole should be drilled on the firewall. Both sides of the firewall should be clear of any obstruction before the drilling is done.

Red Wire – this wire is the third to be connected. It is connected to the non-powered stop lamp wire of the brake light switch, which is the wire that carries a signal when the brake pedal has been engaged. The connection should be made through a quick splice, and this supplies the required power once the brake pedal has been pressed. It is advisable to install an inline fuse between the red wire of the controller as well as the stop lamp switch. Failure to install the fuse may lead to the damage of the brake controller.

Blue Wire – the blue wire is connected last. The wire offers the required output to the trailer brakes, which is basically the required braking power to the tow vehicle connector.

All the controller wiring connections should be done to the wiring harness before the harness is connected to the vehicle. Finally, when the brake controller has been connected and mounted properly, the loose and excess wires should be zip tied.

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