Warning indicator light and buzzer for low air pressure after install new air dryer??

[Oldworldtenacity]

So, I had to bypass the lines when my air dryer valve got stuck open back FEB in 15 degree weather driving it back home from GA.

The low pressure indicator light would always flash and the buzzer would buzz and then once you bypass it it stops working...which I think is normal(although I could be wrong).

Anyways, got the new air dryer put on today and it works fine...however, the light and buzzer will still not work.

Any input as to what the problem may be?

 

[Oldworldtenacity]

Ok, I have just been informed that there is a failsafe module that gets pressure readings from senders on the air tanks.

Does anyone know how you can verify that the failsafe module is working properly...or the senders?

 

[juanprado]

The newer series Tm -23 5 part repair series has wonderful trouble shooting flow charts. They can be download on this site. There is one specifically work package for the fail safe module.

It works with 2 pressure sensors on the primary and secondary air tanks and also the parking brake sends it it a signal. Make sure all your grounds are also nice and clean. They can be a bear to troubleshoot. There is actually 3 different styles and manufactures of the fail safe module. I believe the all plastic one is the best of the bunch. One is all metal smooth can, another is a metal can with built in cooling fins.

Artisin wrote up an extensive write up on his trouble shooting.

 

[Oldworldtenacity]

Ok thanks. I will look into the TM for that info.

 

[Bandit02]

I need that flowchart as well. Since I bought my truck the fail safe has been unplugged, when I plugged it back in the park brake light/buzzer stay on (even with the PB off). The low air light works correctly.

 

[Oldworldtenacity]

I just looked for it and can't seem to find it...first time I have even looked in that section...so it all looks foreign to me.

juanpardo can you paste the link that the exact TM is under in the TM section?

 

[juanprado]

You need work package Wp 110 pg 936 of Tm 9-2320-272-23-1; 24mb download

http://www.steelsoldiers.com/showthread.php?121487-TMs-for-M939-Series-Trucks

Post what you find

 

[Oldworldtenacity]

You need work package Wp 110 pg 936 of Tm 9-2320-272-23-1; 24mb download

http://www.steelsoldiers.com/showthread.php?121487-TMs-for-M939-Series-Trucks

Post what you find

Yep found it, Thanks! There is a lot to go through with this issue and everything is about the low air pressure buzzer not wanting to shut off...so different then my issue.

I have at least gathered that I should check if the low air pressure switch is working properly and to inspect wire 57 and 578A though.

Not really anything more after reading through the 12 pages or so.

 

[Oldworldtenacity]

Ok, so I checked the low air pressure switch and it is working fine. I also realized that the low air pressure is working correctly and shuts off after it reaches 80PSI.

The light is still not flashing though and the bulb is good....because I tried it in the parking brake socket and it worked fine.

Any ideas why the light still wont work?