Troubleshooting Brake Controller Not Working When Brakes Are Applied but Works With Override Switch

Question

Question:

My trailer brakes will not work when appying the truck brakes but will work when you push the test button on the controller box! Does this mean my box is bad or what?

asked by: Sarah

0

Expert Reply:

This sounds like the trailer brakes are not receiving the signal from the brake controller when you apply the brakes. I believe what is happening is that you may have a loose, broken, or inaccurate connection on the red wire from the brake controller.

The red wire needs to attach to the stop light switch above the brake pedal. It connects to the wire on this switch that carries a signal ONLY when the brake pedal is pressed. It should not have a signal at any other time. Use a circuit tester, like # PTW2993, to test the wires. If your brake controller red wire is not connected to the correct wire, or is loose or broken, this would cause the problem you are experiencing.

When you use the manual override, it bypasses the need for a brake signal on the vehicle and applies power to the trailer brakes. That is why it works when you hit that button.

If you find that the red wire is connected in the right place and is not loose or broken, then this is probably a problem with the internal circuitry of the brake controller and it will need to be replaced.

I have included an FAQ article on brake controllers and a video on testing a brake controller that might be helpful as well.

expert reply by: Michael H

0

Ed

2/1/2020

2014 F250 Super Duty. I removed the brake pedal switch and looked for a red wire in and around the switch. There isn’t a red wire. There are 4 wires going into the switch. White/red, purple/orange, black and purple/white. There are no other wires connected to the switch or any empty connector for another wire. Suggestions?

Reply

Jason S.

2/3/2020

The red wire he was referring to is on the brake controller. Because you have a 2014 Ford F-250, I recommend you use the wiring harness already existing in your truck. I've linked the page for you so you can match your factory plug as well as you brand controller. If you don't see your brand, then use # 3034-P and then you can just cut the black connector off and match color for color with your brake controller to splice in. If you have the 7-way on your truck, you'll be all set. If you have the 4-way trailer connector, then you will also use # 37185 and an additional length of wire # 12-2-1 sold by the foot will be necessary to connect the 7-Way socket of part 37185 to the vehicle's tow package wires which are along the rear frame rail.

Helpful Links

bc-2014_Ford_F-250+and+F-350+Super+Duty.htm?style=with+factory+7-Way

Reply

Daniel Z.

7/21/2020

Hi, I installed my Tekonsha Prodigy brake controller in my 2007 Escalade. I pulled the wires down from under the dash and hooked them up according to etrialer.com'structions and the instructions on the label wrapped around the wires. I also hooked up the wires to the studs under the hood. Checked the fuses for the studs and all looks good. The controller shows a "C" for connection when it is hooked to the trailer and the brake lights work on the truck and trailer. However the electric brakes will not engage when the pedal is depressed. I can get them to engage by applying them manually with the lever on the brake controller. I used a test light on the wire coming from the brake switch and there is no signal there even when the pedal is pressed. First thing I did was go buy a new brake switch. I changed that and still I have no brake signal. Any suggestions or help would be great.

Reply

Chris R.

7/27/2020

This is actually pretty strange, especially since you now know the brake switch on the Escalade is good. I will say that since the Prodigy is a proportional controller, stepping on the brake pedal while parked will NOT engage the trailer brakes. You'll need to actually be moving (and decelerating) for power to be sent back to the brakes with the pedal. The only thing I can think of is to try and find another wire that carries power only when stepping on the brake pedal such as the 3rd brake light circuit and tap into that with the Prodigy's red wire.

Reply

Chuck

5/17/2024

Hello, Will a bad brake light switch on the brake pedal cause the control to not work properly? My trailer brake control was working until my brake light switch started malfunctioning. Also, I had the same results with my other trailer brake control. Thank you.

Reply

Jon G.

5/24/2024

@Chuck Yes, a bad brake light switch will cause your brake controller, and ultimately your trailer brakes, to malfunction. The brake light switch tells the brake controller when to send a signal to the trailer brakes. So if the brake light switch is malfunctioning then the controller won't be able to accurately tell your trailer brakes when to activate.

Reply

W. J.

3/14/2025

I would like to see the FAQ and video but do not see the links. Can you send them or repost? Thanks!!

Reply

Robin H.

3/15/2025

@WJ it is pretty far down on the page. If you scroll down past the comments you will see them under "featured help information."

Reply

W. J.

3/15/2025

@RobinH Thanks!!

Reply

Answer 1

Sounds like your brake controller will apply your trailer brakes if you apply the manual override lever but not when you press the brake pedal. This is a fairly common problem and the solution is the red wire of the brake controller. Make sure it is…

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Answer 2

If your trailer brakes activate when using the manual override but not when pushing on the brake pedal you may have a bad connection or a faulty brake switch. I have also linked below our article on Brake Controller Troubleshooting. Also if you have…

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Answer 3

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Answer 4

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Answer 5

You are correct, you should only be getting output when the brake is applied, or the override switch is activated. It sounds like the controller might be bad, but to make sure, you should probably bench test it before tossing it. Use a circuit…

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Answer 6

The best air bag suspension enhancement kit that fits your 2022 Ford F-250 is the Firestone part #F95FV. This bag set has the highest towing capacities and also has the best air bag quality constructions as well. It will do a great job giving your…

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Answer 7

The first thing to check on your 2011 Silverado is your fuses. If you have a 1500, then you will want to check fuse numbers 3, 6,10, 25, and 68. I can't find the online manual for the 2500 or 3500 of that model year, so if you have that model,…

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Answer 8

All the brake controller needs to sense a trailer connection so that you can test it is a slight amperage draw on the output circuit. For that you can use a circuit tester like the part #PTW2993 with one pin grounded and the other on the output pin.…

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Answer 9

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Answer 10

You can use the breakaway to bleed the brakes on your trailer. If the battery is fully charged, you just need to pull the pin and it will engage the brakes on your trailer. You want to make sure you have someone checking to make sure the reservoir…

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Answer 11

You would not be able to charge your battery through the wiring on your 4-way trailer connector. Since your truck has a 7-way connector, you could maintain the power to the battery but not charge it. To begin, you would need to cut off your 4-way…

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Answer 12

Its not uncommon for there to be slight voltage drop off over a certain distance but with the brake controller set to the maximum you should still be getting 12 volts at the brake magnets. We need to determine if the low voltage is coming from the…

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Troubleshooting Brake Controller Not Working When Brakes Are Applied but Works With Override Switch

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