Air Dump Valve Sticking

[VinceB]

My coach failed to air up.  After a couple of days sitting, it then air up like always. Since then I've been afraid to dump the air.

I took it to my mechanic and he says that when it was sticking there was no 12 volts to it.  So he thinks to start with the dash switch.

But my question is that if there is no 12v then would not the valve close and let the bags air up?

[Happycarz]

Vince, you are correct. You apply 12v to the dump solenoids to open them and dump air. There are two solenoids in the rear and one in the front. You would need all three dump valves to fail.

Start looking at the compressor not supplying air to the tanks. More than likely not the compressor, maybe air drier or governor issue.

As a side note, the compressor has a shuttle valve in the head that gets gummy, and compressor won’t build pressure. Cummins has a service procedure to free it up. I’m the only one I know of that had that issue, though. I replaced the head and toyed with the take-off to see what ailed it. Only then did I find the Cummins’ procedure to remedy it.

 

[Rick A]

 “Only then did I find the Cummins’ procedure to remedy it.” Where is it? Could you post the details?!

[Happycarz]

I’ll look for it and post it. Edit: Found it.

https://quickserve.cummins.com/qs3/portal/service/manual/en/4021418/

Cummins QuickServe

  Services (at top of page, in red)

    A page opens. Go to the second section and click on “Troubleshooting and Repair Manual.”

      Section 12 Compressed Air System

        Air Compressor Carbon Buildup

          It then explains how to do it and what tools needed 

Let me know, as I am curious, if above link will open for you, as I am signed into QuickServe with my credentials. I don’t know if post my link will open for you. Please post back.

Regardless, if it doesn’t work, just sign into QuickServe, follow the trail I posted above.

 

Edited April 10, 2023 by Happycarz

[VinceB]

UPDATE:

Replaced the front dump valve and 2 on the rear along with the dash switch. 

It was a comedy of errors. The switch had corrosion on the terminals. So once the switch was replaced, we got rid of the intermittent nature of the problem and zeroed in on the front valve that was sticking.

Because the rear valves were tied to the same switch (same number of duty cycles) we installed new valves there too along with all the associated fittings. Works as new and doesn't leak down overnight like it used to.