Troubleshooting Prodigy P3 Brake Controller that Shows Low Voltage without Brakes Applied

Question:

I just bought this brake controller and had it installed on a 2009 Ford ranger. I had it professionally installed at a hitch and trailer shop. They had no wire everything from scratch. It always shows voltage 1.1-.6 even when The brakes are not applied. It does this with or without the trailer connected. Then when I do the manual break lever it’ll turn to zero and then fluctuate back to around .6. Shop said it’s a faulty brake controller even though it’s new. I don’t want the brakes to be applied to the trailer while I’m driving and burn them out so do you think it is bad wiring or brake controller? Thank you

asked by: Gabe

Expert Reply:

The P3 brake controller part # 90195 under normal circumstances should not be behaving like what you described. It normally would be showing you error codes on the display though if it has an internal problem or was wired up wrong.

So what I think is going on is that the stoplight circuit (red wire) has power ran to it at all times and the boost function is running it's base brake output at all times. So I would verify with a circuit tester like part # PTW2993 that the red wire only has voltage when brakes are applied. The person you had install the controller should be who fixes it but if my suspicion is correct you'd want to instead find the correct stoplight circuit to run the red wire to.

I attached a help article on troubleshooting brake controllers for you to check out as well.

expert reply by: Jameson C