How to Test Brake Controller that Had Stoplight Circuit Short Out


Purchased a vehicle with a draw tite activator II brake controller already installed- recently, I noticed that the decimal point no longer appeared when applying the brakes no trailer attached. Didnt think much of it. Today, a guy pulled up along side me and told me I had no brake lights. Upon inspecting, I noticed that the brake lights would work if the manual slide was pressed but not with the brake pedal. I looked at the wiring under my dash and saw the red wire had been improperly installed not allowing enough slack behind the brake pedal and the repeated use of the pedal had worn though the plastic coating and was causing a short see attached photo. I fixed the issue and coated the wire with e-tape but I still have the same issue with the brake lights. I have checked all fuses related to brake lights and they all are fine. My questions are could the short have fried something inside the controller and how would I go about testing it? Thank you


Expert Reply:

It is possible that the controller is damaged but it's fairly simple to test the controller to know for sure.

Testing the brake controller is fairly easy. Sever the blue brake output wire near the brake controller leaving enough room to reconnect it and then apply the manual slide. Using a circuit tester like the Quickee Tester, part # ALL640595, you should get output to the controller side of the wire you severed. If the manual slide activates the trailer brake output wire properly, try the brake pedal. If the brake pedal activates the brake output properly also then the problem is farther back either in the vehicle wiring or on the trailer.

If either the brake pedal or the manual slide are not functioning properly you will need to test the wires going into the brake controller. Make sure you have power entering the brake controller on the black wire. On the red wire you will only want power when the brake pedal is pressed.

If there is power on the red wire before the brake pedal is pressed you have connected the red wire from the brake controller to the wrong circuit. You would then need to find the brake switch wire that has power ONLY when the brake pedal is activated.

If these connections check out and the brake controller is properly grounded then there is possibly a problem inside the brake controller.

I am including a link to a video that will show you how to test the wiring on a brake controller.

For a brake controller replacement I would recommend the Prodigy P3 Brake Controller part # 90195. This is our best selling brake controller because of how well it works and how easy it is to setup. This is a proportional brake controller that senses the amount of braking the tow vehicle is applying and applies a proportionate amount to the trailer brakes. This will be the last brake controller you buy. It can easily be transferred to future vehicles as well.

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expert reply by:
Jameson C

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