LED Light on Hayes-Lemmerz Brake Controller Only Lit When Vehicle Lights are Turned On  

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Expert Reply:

Did you hard wire the brake controller to your vehicle, or did you use a plug-in wiring adapter? If you hard wired the unit, it is possible that you are tapped into the wrong wire for the stoplight switch function (red wire). You will need to use a circuit tester, like part # PTW2993, on the wires coming out from your brake pedal to find the correct connection point.

The correct wire will only get power when you press the brake pedal, and it will go cold when you release the pedal. You can first check to see if this is the problem by testing the red wire right behind the brake controller. Do you get a reading when you press the brake pedal, but nothing when you release the pedal? If not, you need to keep looking for the correct connection.

Was your truck wired with a 7-Way plug from the factory? If so, I would recommend opening up the front and back sides of the plug and looking for white or green corrosion, which could be causing a short. If you see any, thoroughly clean or replace the plug.

It will be best to work on the brake controller and vehicle side of the setup, without your trailer connected. This will allow you to work piece by piece and narrow down where the problem is initially occurring. If you see that you are getting the correct reading on the stoplight switch wire behind the brake controller, move back and test at the 7-Way plug. If you get a reading in the back of the truck when the brake pedal is pressed, you at least know that the signal is getting that far.

If you do get power back to the 7-Way plug, you will then need to move on to the trailer and look for a short. The most likely culprit would be a bad brake magnet, short on the electric brake wire, or possibly a bad ground on one of the lights, especially the brake lights. Check along the wiring for any nicks or rubbed spots and wrap them with tape if you do see any.

You will also want to check the connection of the ground wire coming off of the trailer plug and make sure it is firmly attached to a clean, metal area on the trailer frame. Most trailer lights ground through the mounting hardware, so check each light for corrosion on the studs and clean off or replace any trouble spots.

This would be the best way to start troubleshooting. If you could provide some additional information on the installation I would be glad to give you some additional suggestions. You can view some additional tips on wiring a brake controller at the included links, if needed.

expert reply by: Sarah L

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