Why Does Prodigy P3 Brake Controller Only Show Small Voltage Spike when Pedal is Pressed

Question:

I have a 90195 controller installed in a 2005 Ford F-350, the trailer is electric over hydraulic brakes, I have the controller set at 11.9 and that will read when I use the thumb control. When I use the brake peddle it reads 1 to 3.5 take foot off peddle move tilt the controller up or down it then will read 11 or better, take foot off peddle and wait about 20 seconds and when applied it reads back to 1to 3.5. I just replaced the controller cause the other one was doing the same thing.

asked by: Ken K

Expert Reply:

If you are testing your Prodigy P3 # 90195 while the vehicle isn't moving this is why it's reading a lower number when you press the brakes. The controller needs to sense you hitting the brakes in the tow vehicle before it will start applying the trailer brakes so if you are parked and test it you'll only see the initial boost of voltage when the it senses you pressing the brake pedal. This also is why you'll see the voltage change if you move the controller around with the pedal pressed.

expert reply by: Jameson C