Troubleshooting A Demco Air Force One Braking System Indicator Light That's Always On

Updated 05/28/2025 | Published 05/03/2024

Question:

It works good, but the brake indicator light stays on. The air cylinder does not return to the neutral position.

asked by: Larry

Expert Reply:

Hi Larry,

If the indicator light is constantly on then it's likely just the placement of your reed switch on the air cylinder itself. The reed switch detects magnets and closes the circuit, sending power to the indicator light. Try moving it further toward the end of the cylinder (closer towards yourself). When installing the reed switch it's important to be careful because the reed switch can arc to ground, it will either no longer work or cause the LED to stay illuminated at all times. If you remove the reed switch from the cylinder does the power stay on?

When you say it doesn't return to the neutral position this leads me to believe you have an issue with the cable, whether it's just too tight or that it's snagging on something. I'd check the positioning of your cable to ensure it's straight and that it's not too tight.

This is an expensive piece of equipment designed to make sure you can safely tow your vehicle so don't just accept it not functioning as it should. If you still have issues reach back out to us or Demco so we can get you up and running as you should be.

expert reply by: Kevin C

Dan G.

9/4/2024

hi Kevin - i just had a 2nd vehicle kit installed by professionals. it's the 2nd kit they have installed for me. i then personally installed the transmitter/receiver for the reed switch. i'm having the same issue that i think Larry was trying to explain... it's all working properly, but when i let off the brakes the actuator (aka air cylinder) is not returning all the way back in, so it's keeping the reed switch activated. it's not actually pushing on the brakes... it's just not returning all the way back in. if i reach in and push the actuator all the way back in... then the reed switch goes off and the receiver in the RV goes off. is this an issue with the cylinder... does it need to be lubed maybe? or is it an issue with how the cylinder is mounted... maybe it needs to be mounted further out so the brake pedal going back to "off" pushes the cylinder all the way in? or... other issue?

Kevin C.

9/5/2024

@DanG I would start by activating the system so that the cylinder sticks and causes the issue. From there go to the main unit and press in on the output air line and remove it from the main unit. If this allows the last bit of air to escape the cylinder and shut off the light then we know you just have a venting issue. There should be a vent that's right next to the output line that could be blocked and need to be cleared or would need to be blocked depending on the style of brakes the towed vehicle has. You could also just have an issue with how the cylinder is mounted to the brake pedal or the tension it has with the pulley. I would play around the tension by moving the cylinder in the bracket to see if that's the case. We've also seen some vehicles in the shop where it will stick like yours is and just working the cable in and out over time with use has solved the issue. Lubrication with a dry lube spray might help as well. The angle of the cylinder will also come into play so I recommend checking out the instruction manual to ensure you're following their directions on how the cylinder needs to sit and ensure that your pulley cable is straight and not binding up on anything. I would also check for any burrs in the line as we've had a few instances where there was a burr preventing the cable from fully sliding back and forth. Test out these things and let me know what you find, if the issue persists then we can keep troubleshooting.

Dan G.

9/13/2024

@KevinC Thanks for your reply. i initially found that there was quite a bit of slack on the metal wire. i took some slack out and when testing it manually it seemed to be fixed. today i hooked it up to the RV for a final test (i leave on a trip on Tuesday) and it was still "sticking" from retracting all the way and the light on the reed switch staying on. I didn't yet try out removing the output air line from the main unit to see if that would solve the issue. the unit doesnt seem to be mounted exactly per the instructions, but possibly the specifics of the '24 F150 don't allow it to be installed exactly per instructions. I took a video showing the issue that i put on my youtube. i will post the link here and hopefully you can see that. the installer is an hour away from me, that is why i've been trying to solve myself. if i cannot solve this weekend, i'll need to bring it to him monday to try to resolve before we leave on our trip. i can confirm that the unit is pressing the brakes properly, and releasing them all the way. i had someone watch the pedal move and try to pull it up after it was released to see if there was play, and there was not. so the unit is functioning properly, but since the actuator is not coming all the way back in... the reed switch stays lit. https://youtu.be/hV58KSnxhPU

John S.

5/28/2025

@DanG Did you ever get this sorted out? I'm having the same issue. I was going to try to alter the angle, slack, etc. to see if anything will allow the light to turn off... Thanks, John