Troubleshooting Tekonsha P3 brake Controller No Output With Brake Pedal

Question:

I have had the p3 for a number of years worked well last couple of years had not been used attached to small caravan didn’t work so bought a new tekonsha voyager Both controllers know trailer is there both work on manually but nothing without manual lever brakes on caravan are good Have checked most connections replaced one of trailer connections Would you be able to give me some ideas Thanks

asked by: Chris O

Helpful Expert Reply:

The # 90195 P3 and the # 39510 are both proportional controllers, so if you're testing for brake controller output with the brake pedal is pressed, you're not going to see any voltage with the brake pedal unless the vehicle is in motion.

You don't mention the year, make or model of the vehicle in question, but if you're not getting output from the controller while the vehicle is in motion, you might have a bad stop lamp switch or a blown fuse on the 3rd brake lamp. The stop lamp switch or the 3rd brake lamp circuit (depending on the vehicle) is what alerts the brake controller that the vehicle is braking, and if you're not getting signal in on the red brake controller wire with the brakes, you won't get output with the pedal. Early to mid 2000's GM trucks and full size SUV's had a known issue with bad brake switches, so this could be your problem.

I'll link to a brake controller troubleshooting guide that you might find helpful.

expert reply by: Mike L