ABS brakes

[sermis]

I still can't figure out the brakes on the M944. The dash light is blinking and buzzer going off. Air builds to 90-100 psi and truck will slide to a stop. I don't hear any major air leaks but the buzzer and light will not shut off.
The ABS light on the dash is also on. Should the light be on or off?
Any ideas here?

 

[emmado22]

Call these guys....

https://www.absmodtrack.com/m939/Des...ndex=0&tabid=1

 

[Cdub]

Hi,

It sounds like your " Low Air Warning Switch " is not working the way it should. There are two air pressure electric switches wired in series. There is one on the primary and one on the secondary air tanks. The primary and secondary air tanks are located under the passenger side door. If there is not 60 psi in either tank the light and buzzer will stay on.

Once the air pressure is over 60 psi in both the primary and secondary air systems. Remove the wires from one of the low air warning switches and use a wire to jump out the switch. If the light and buzzer goes off then that switch is bad. If the light and buzzer stays on then the other switch is bad.

I had removed both switches and sprayed some WD-40 in the small hole of the switch and blew them out with some compressed air. Both of mine have been working properly ever sense.

Cheers,

C'dub

 

[sermis]

OK I checked the switches. The switch on the top tank is bad. Jumped it out but the buzzer / light are still on. I noticed that the secondary tank was slow to fill this time.
Any more ideas? Right at 90 psi in both tanks.

 

[sermis]

This truck has had some type of front end accident so it is possible that something is broken in the system somewhere.

 

[Cdub]

Sounds like you have either one or two bad Air Pressure Switches. They will need to be replaced. When both switches are in the closed position @ 60 psi are in series and go to ground to turn off the light and buzzer. If you jump out both switches the light should go out.



NSN 5930011890494 Switch, Pressure


Cheers,

C'dub

 

[sermis]

I jumped out both switches and it still buzzed and flashed. Unless the ground is not good.

I left the truck Idle for a bit and went back out and the secendary tank showed 0 psi. It had droped from 90psi. Not sure if the guage is bad or it is loosing air. I think if it was loosing that much air I could hear it.

 

[emmado22]

Do some looking at the website I posted.. Those are the people that made the ABS kit.. There is ALOT of info there.

 

[sermis]

Thinking back I think I closed a black valve near the air tank. Might be the cause of no air in secondary.
I am just trying to get the truck ready for it's trip to Nebraska next week.

 

[Cdub]

I jumped out both switches and it still buzzed and flashed. Unless the ground is not good.

If you think the ground may be bad then you can use a jumper from wire 578 going to the first switch at the primary tank to the frame for a good ground.

If the light and buzzer is still on at this point. Then I would do as Mark suggests.

Cheers,

C'dub