Troubleshooting Weak Output from Trailer Brake Controller When Pedal is Pressed

Question:

When the break is applied I only get 1.6 volts at trailer pin, but when I slide the trailer break manually I get 13.5 volts at trailer pin whats going on?

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Expert Reply:

With a trailer brake controller either pressing the pedal or pressing the manual override lever should cause the unit to generate the same output signal so long as you are moving. If you happen to have a time-delay type controller like the Curt Venturer # C51110 the unit should generate the same output even if you are still. But with a proportional type controller like the prodigy P2 # 90885, that uses a sensor to detect your motion, the output level from pressing the pedal will depend on the detected rate of deceleration, but the unit will output full selected power if the manual override is used to activate it.

One potential cause for this is a loose connection at the red wire, which brings the brake light switch signal in to tell the controller you're slowing down and need the trailer brakes to engage. If this wire had corrosion or was loose it might not be able to deliver the full triggering signal to tell the controller to output full power. Check that the red wire's contacts are clean and secure. If the installation uses a quick-connect adapter that plugs in under the dash then unplug it and check all contacts for the red wire. Look for corrosion or perhaps a pin that is bent and not making full contact with the contact in the mating connector.

If you have a circuit tester like # 40376 you can test the red and blue wires at the back of the controller. Test the red wire when you press the brake pedal. You should detect a full-scale brake light signal, close to 12 volts. If you find this signal on the red wire, repeat the test on the blue wire while you press the pedal with the controller set for maximum power and boost. If you detect a weak signal at the blue wire then the unit has internal damage and should be replaced.

Please tell me which controller model you are using and also the details of your vehicle and I will be glad to assist further if needed.

expert reply by:
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Adam R

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