P3 Brake Controller Will Not Send Back Enough Power to Trailer Brakes when Going Down Hill

Question:

Ok Ive got a real head scratcher here.. bear with me please! Well Im finally towing a trailer and trying to get the brake controller to work properly. Im really scratching my head on this one. And was hoping for,some advice... For some reason when Im going downhill the brake controller does not send power to the trailer brakes. It works when level, and on inclines... but going downhill nope.. the controller is sensing the brake light power when the pedal is depressed but it fails to send power to the brakes. The wiring seems fine and all as I can manually apply power to the trailer brakes via the override switch. So the wiring is good but for the life of me I cant get this controller to work downhill consistently. I originally thought I had a bum controller so I ordered a new one same model and it does the same thing... I even went a step further and talked to the MFGR and sent the controller back to them for testing explaining what I was good no thru. They tested it and it is fine....so controller is good. I even went a step further and bought a completely different model from their product line. Tekonsha and guess what.. same thing happens... As a last ditch effort I thought it may be the location of the controller and maybe it was picking up some interference.... so I moved it on top of the dash and even to the passenger seat.... guess what. Going downhill no brakes. So I am starting to suspect the wiring or something other than the controller. But the kicker is it works just fine level, up hill, manual override etc... just downhill it refuses to send power to the trailer brakes unless I cycle the manual override and then it works until I take my foot off the brakes and apply again then it does the same thing. Do you guys have ANY idea what it might be? It just does not make sense to me. Im going to try a completely different manufacturer of proportional brake controller as a last gasp. And if that does not work will go with a time delayed controller for which I would rather not do as they arent as good as the Tekonsha proportional ones I have been trying to get to work. Sorry for the long e-mail. Can you help me get this figured out.....? Any ideas?

asked by: Daniel G

Expert Reply:

I ran this scenario by some of the other guys here and we came up with the same conclusion as to why this issue might be happening. Since the P3 # 90195 and other similar controllers rely on deceleration to determine the amount of power to send back it would not send much power back if you are going slow down hill like you would on gravel, dirt, or extremely steep pavement.

Testing that would require going a bit faster down hill and applying the brake pedal. If it sends more power back then the issue was not enough deceleration.

Another thing you can try is to ramp up the power output when you are going down hill. It is possible that, if going slow enough, the controller won't send back the amount of power you are expecting. Turning the power up would provide more voltage back to the brakes. You could also turn on the boost which will start the braking voltage higher (but still only ramp up to what you have it set to).

Give those things a try and if that doesn't work and another brand doesn't work then a time delay controller would be the way to go because it would send back the same amount of power no matter how much you are braking down hill, up hill, side ways, flat, or other!

expert reply by: Michael H