Troubleshooting Reese Brake Controller That Activates Only When Manual Override Lever is Pressed

Question:

The slider control is working it will stop the trailer and the indicator light turns yellow to red when applied. But does not when you apply the breaks, light stays green and the trailer brakes are not engaging.

asked by: Randy J

Expert Reply:

Since the manual override lever on the brake controller does activate the brakes but pressing the brake pedal does not, this tells us that the controller is functioning internally but that it may not be getting the required input trigger signal that tells it to generate output when the pedal is pressed.

On a brake controller such as the Prodigy P2 # 90885 the red wire is the input signal wire that tells the unit to power the trailer brakes. This red wire needs to connect to the pedal's brake light switch, to the cold side of the switch that carries voltage ONLY when the pedal is pressed and at no other time. Some wires in that same area may carry voltage when other vehicle functions are activated. First make sure the correct wire is connected to the red input wire. You can use a tester like # PTW2993 to find the correct wire to provide the input signal.

I also linked two helpful articles concerning brake controller installation.

expert reply by: Adam R