Troubleshooting Quest Brake Controller Malfunction in 2012 Dodge Ram 2500

Updated 05/02/2017 | Published 05/01/2017

Question:

I have a 2013 dodge 2500 and using the quest trailer brake controller and the factory harness but I have a constant 4.5 volt on trailer brake wire causing the brakes to lock up

asked by: Tim

Expert Reply:

I suggest you start your troubleshooting at the brake controller's wiring. The blue wire from the back of the controller carries its output signal that is routed to the pin at the 5-o-clock position on the 7-way. Please refer to the linked photo.

There should be a signal on this blue wire only in two circumstances: when the red input wire that connects to the brake switch carries a signal that tells the unit to generate brake power; and when you press the manual override lever on the controller, as you would in an emergency stop situation.

If your controller generates output on its blue wire at any other time, and you can detect this at the back of the controller using a tester like # PTW2993, then the unit itself is damaged or it is connected to the wrong input signal. The cold side of the brake light switch, the side that goes hot ONLY when you press the brake pedal, is where the controller's red input wire should connect.

Another possible cause is simple corrosion in the trailer socket on the vehicle or in the plug on the trailer. Connectors can develop corrosive build up and this can even occur inside a plug. If this gets bad it can cause two separate circuits to become bridged together. If for example, the 12V power circuit bled over to the brake circuit, this would cause the brakes to engage even if the controller didn't send a signal telling them to do so.

Please refer to the two linked articles for more help in diagnosing this problem.

expert reply by: Adam R