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Troubleshooting Low Brake Controller Output Voltage


I have a 1885 yes it really is an 85! still running good. C30 dually. pulling 3 axel gooseneck enclosed trailer. the truck has an old hydraulic controller. I am only getting 6.4 volts to the trailer when the controller is on full power with the manual lever. should I have closer to 12V when maxed out? Not sure where the problem is but I do not have enough power with 6.4 V to get anything but very light drag on the wheel when it is off the ground. the magnets are working and the 6.4 is not at the magnet but out of the controller itself. looking at the Teconsha P2 series controller. would this be a good solution for this application? Please respond asap I am trying to get this set up for some testing at the track soon.... appreciate you prompt reply... Thank you! :


Helpful Expert Reply:

The first troubleshooting step is to check that the controller output is correct before it travels through the vehicle wiring to your 7-way. Cut the blue wire a few inches from the connector at the back of the controller. Apply your grounded circuit tester to the blue wire coming from the controller and press the brake pedal. If you do not detect a full-strength brake output signal on the blue wire, then you will need to check the other connections to the controller. (This could also indicate a damaged brake controller.)

Next you can inspect the connections the brake controller is making to the factory wiring of your truck. You can next check the red wire to the controller. This wire carries the signal from the brake pedal switch that tells the controller to generate a brake signal for the trailer. You should detect a signal on the red wire only when the brake pedal is pressed.

If the controller is generating a full-strength braking signal on the blue wire (close to 12 volts) and the wiring is good then you know the problem is somewhere in the vehicle wiring downstream of the controller and connection port. In this case reconnect the cut blue wire and securely tape it.

Next inspect your 7-way connector for signs of bent or damaged pins, corrosion or trapped dirt or moisture. Sometimes trapped road dirt or water can bridge two circuits, causing a short. Follow the wiring forward toward the OEM connector on the driver-side frame rail, usually between the back tires and the rear bumper. Please refer to the photo provided. Again, check that this connector is in good condition. You can use a circuit tester (like # PTW2993) to see if the brake signal is reaching the OEM connector by testing the blue wire that leads to it from the front of the vehicle. If there is a full-strength signal reaching this point you will need to replace the 7-way.

I attached an FAQ article on troubleshooting brake controller installs for you to check out as well.

If the controller is bad the Prodigy P2 Brake Controller part # 90885 would be an excellent choice for a controller.

helpful expert reply by:
Jameson C

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