Troubleshooting Dim Light on Hayes Air Actuated Trailer Brake Controller

Updated 04/09/2024 | Published 05/13/2023

Question:

I recently installed the Hayes 100400c automatic electric brake controller, air actuated in my Peterbilt. Everything is wired correctly and plumbed correctly but I am not getting a brake signal in the blue wire when stepping on the pedal, the manual lever moves and the light comes on but nothing to the blue wire. Tired moving the manual lever by hand, no light and no power to the blue wire. Could the controller be bad?

asked by: Vince B

Expert Reply:

There's always a possibility that a brake controller is bad if things aren't working properly, but more times than not something was accidentally overlooked or a connection isn't made just right (bad grounds and loose connections are pretty common) so a few tweaks to the setup usually fixes the problem.

When it comes to the Hayes Air Actuated Trailer Brake Controller # HA100400C it looks like the instructions have a few things at the start when it comes to that indicator light:

"Under a no-brake situation, the light will remain off. As brakes are applied (either automatically or manually) the indicator light will illuminate with a varying degree of intensity from dim to full brilliance. Light intensity will be directly proportional to brake application."

and

"NOTE: If the controller is mounted to a plastic instrument panel, it may be necessary to ground controller case for the indicator light to operate correctly."

I would try checking your ground to make sure it's secured to a good place and then also make sure you're looking for the indicator light to be operating like it should be - even if it's dim.

expert reply by: Jon G

Jammy

4/9/2024

Great tips, I have a different scenario. I have my unit hooked up it was working perfect but had an issue with the black wire getting cut. When I reconnected it the brake lights do not go on. Yet the turn signal work. I tried to check the power and it is not getting power when I push on the brake and use a wire tester. The box light t does work

Jon G.

4/9/2024

@Jammy The black wire on the Hayes Air Actuated Trailer Brake Controller # HA100400C is only for the 12V power and should be connected directly to your battery so if you aren't seeing power on that wire then you'll need to trace that wire to the source and replace any damaged or broken wiring to fix the issue you're seeing for power. Your brake light circuit is a completely different situation since it isn't connected to the same function as your 12V power you'll need to trace the brake light signal and look for any damaged wiring or connections there as well.