Troubleshooting Tekonsha Mark 12 Brake Controller that Red Light Stays Lit Up all the Time

Updated 03/11/2015 | Published 03/10/2015

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Question:

My 1994 ford F250 recently indicated a constant red lamp on the controller itself. I check power blk wire and brake red wire and blue wire that showed an output when I forced the controller. Any reason the lamp should be laminated when the key is turned on? Maybe my controller had and internal problem? Konsha 2030 comments: Thanks

asked by: Jeffrey A

Expert Reply:

The Tekonsha 3020 Brake Controller you have is an older model that was called the Mark 12. The problem you have could be due to corrosion on the trailer connector, first check for that and clean as necessary. Due to the age of your controller it may have shorted out. Here is how to test it to determine this:

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 part # PTW2993, 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.

If the controller is bad and needs to be replaced I would recommend the Prodigy P2 Brake Controller part # 90885. This is our best selling brake controller because of how well it works and how easy it is to setup.