Ground Error and Weak Trailer Brakes Using P2 Brake controller on a 2004 Ford F-250

Question:

when i step on the brake the controller gives a number on the read out of about 12,+ or _ if i keep my foot on the brake at a light the number starts to decrease , also now i am getting the code for controller not seeing ground,but this is not all the time.this is on a 2004 ford f250 which had the pins for a brake controller, would it be better to go directly to battery ground to eliminate the ground problem if so would #12 wire be okay. also at the highest setting it will not lock up the brakes,this is a #8000 travel trailer i have even rewired the brakes by running 2 #10 wires down the center of the trailer and branching off to each brake individually ,i think its called balanced brake wiring ,and the brakes are adjusted on a regular bases

asked by: Mark

Helpful Expert Reply:

The P2 brake controller # 90885 will initially hold the trailer brakes when stopped at a traffic signal but will then start to release them. That is normal for that particular controller and many proportional controllers because they have to sense movement to send power back to the brakes.

There could be a weak ground and attaching the ground wire to the battery is the best ground location there is for a brake controller. Using 12 gauge wire will be fine for the brake controller ground wire.

The controller not locking the brakes could be because of voltage drop at the magnets. With the controller set to the highest setting your should be seeing 12 volts at the magnets. If you are getting less than 12 volts then it could be a wiring issue somewhere between the magnets and the controller.

Make sure the vehicle and trailer side connectors are clean and free of corrosion inside, where the wires attach, and outside on the pins. Inspect the wiring and fix any pinched or damaged wires as needed. Also, if at all possible, ground the brake magnet closer to the brake assemblies and make sure the ground location is clean and free of corrosion.

Usually brake magnet wiring is run back to the axle where it will then split and go to the magnets at the front axle (if there is more than one axle) and subsequent brake magnets would be spliced in.

expert reply by: Michael H