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Troubleshooting No Power on the Blue Brake Output Wire from a Brake Controller

Question:

I got no power to the blue wire which is electric brakes I think I got brake controller problem

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Expert Reply:

To determine why you do not have any power on the blue brake output wire, I recommend starting at your brake controller. First, make sure the brake controller is on and receiving power. Most brake controllers have 4 wires, blue (brake output to trailer brakes), white (ground), black (12 Volt power from vehicle battery), and red (stop light switch).

If your brake controller is not on, make sure the black power wire is connected to the vehicle battery via a 20 or 30 amp circuit breaker. Also, check to make sure the circuit breaker has not been tripped. If you are using a plug-in harness and there is no power to the brake controller, a fuse may be blown.

If your brake controller is receiving power, set the power gain to maximum voltage and sever the blue wire about 6 inches back from the brake controller. Using a circuit tester, like part # PTW2993, test the blue wire for power when you activate the manual override of the brake controller. If there is no power on the blue wire when the manual override is activated, the brake controller is probably bad and would need to be replaced.

If you have a proportional brake controller and are testing for power when the brake pedal is pressed, there will be no power on the blue wire. Proportional brake controllers send power when the brake pedal is pressed if the vehicle is moving.

If you have a time-delay brake controller and there is no power on the blue wire with the brake pedal pressed, check the connection of the red (stop light switch) wire from the brake controller. This wire should be connected to the wire from the brake light switch that only has power when the brake pedal is pressed. If the red wire is connected properly and there is no power on the blue wire with the brake pedal pressed, the brake controller is probably bad and would need to be replaced.

I have attached three FAQ articles on brake controller installation and troubleshooting for you to check out.

expert reply by:
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John H

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