Troubleshooting Brake Controller
Question:
I have an older mark12 2030. When I depress the brake pedal, the red light comes on but, the brakes don't come on. When I move the slide over, the brakes come on. Any ideas?
asked by: Bruce W
Expert Reply:
You are going to need to do some testing because of the potential number of issues that could be causing your problem. First you will need to find out if the issue is on the brake controller, truck, or trailer. To test the brake controller, sever the blue wire a couple inches from the back of your controller. Then use a circuit tester such as # PTW2993 to test the end of the blue wire coming out of the controller. It should only have power when you apply the manual override; if it shows power at idle then there is an issue with the controller, and it will need to be replaced.
If the controller tests fine, reconnect the blue wire and move on to the truck side trailer connector. Often, corrosion or dirt may be the cause of a short in a trailer connector. Check the plug to see if there is any type of corrosion built up that may be hampering it's functionality.
You will also want to test the brake output pin; it should only show power with the manual override. If it shows power any other time then there is a short somewhere between the connector and the brake controller you will need to find. If the truck side checks out then it could be the wiring to the brake magnets or possibly the magnets themselves. Inspect the power wires to the magnets and look for wires that may be pinched or otherwise damaged and fix as necessary. You'll also need to make sure the ground wires are attached to bare metal surfaces, free of any paint, dirt or corrosion.
You'll want to visually inspect the magnets; if you can see the copper windings coming through the magnets will need to be replaced. To test the magnets you can follow the help article I have linked. I have also attached some help articles on testing and troubleshooting brake controllers for you to check out.
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