Trailer Brakes Pulse On and Off when Stepping On Brake Pedal on 2014 Subaru XV Crosstrek

Question:

I have a P3 Controller in my 2014 Subaru Crosstrek and Im having trouble when the brakes are applied and the trailer slows to a stop. The voltage on the P3 display fluctuates from 0 to about 4 or 5V constantly and the brakes grab On and Off while the voltage fluctuates causing the trailer to bang back and forth while I stop. If I move the lever on the cpntroller the brakes apply normally with no voltage fluctuation and no banging. Any ideas why my voltage fluctuates causing grabby brakes? Is this a bad controller?

asked by: Mark J

Expert Reply:

Any time there is a problem with a brake controller when using the brake pedal the first thing to check is the connection on the red brake controller wire. It has to be connected to a brake switch wire that only has power when the brake pedal is pressed and not at any other time (such as with the head lights or turn signals). On your vehicle it is likely a brown wire with a white stripe.

There could also be a wire that is related to the ABS (anti-lock braking system) and that might be what your controller is connected to. The wire needs to have constant power when the brake pedal is pushed. If you check the vehicle wire that the red wire is tied to, using a circuit tester such as # PTW2993 that should show you if the wire has constant or fluctuating power.

Also, make sure the controller is mounted within the range specified in the instructions. If it is tilted or turned to the side, it can cause all sorts of strange behavior.

expert reply by: Michael H