Just discovered New Air dryer not working and Compressor runs non stop on M923A2

[Oldworldtenacity]

Ok, so I have not drove the truck much in the past 6 months and actually installed a new air dryer after the old one froze up last March driving it back from auction.

Installed new air dryer and was puzzled because it would not sneeze after first starting the truck and it building to 120 PSI like it did with the original air dryer...but would sneeze every 15 seconds like clockwork once the truck started moving above 20 MPH...or so I thought(more on that in a minute).

I ended up replacing the compressor not long after because it would not build air pressure within about two months of me replacing the air dryer..which I assumed was working,but not working entirely correctly.

Fast forward to last week and a friend tells me that the sneezing sound that I hear every 15 seconds while driving is the purge valve releasing air and not the dryer sneezing. That makes sense because it is a slower type hissing sound release of air vs the typical loud quick pops of air I hear on OTR trucks. He says the dryer is not doing anything at all and that the compressor is also running non stop which I already suspected even though the gauges show 120...and they are accurate because we checked the tanks with a presure sensor months ago. not sure of the wet tank though. He was afraid to dive into why it's not working because of his unfamiliarity with military vehicles and air systems in general.

Please help lol.

 

[Shoprat 19th Engr]

Change the Air Govenor on the Air Compressor this controls the air drier and the amount that the air system builds

 

[sd39u]

Change the air dryer out. Suprman has the one you need for sale in the classifieds. He's very good to deal with.

Eric

 

[MtnSnow]

No need to replace the drier.( the OP says it was already replaced).. I would start with replacing the PPV. Then move onto the governor. Then check the unloader on the compressor.

 

[Suprman]

I wonder if your ppv is stuck then no air to governor and no air to compressor unloader from governor to stop making pressure and the same unloader air feed tells the air dryer to vent the expello valve on the bottom to dump moisture.

 

[Andyrv6av8r]

No need to replace the drier.( the OP says it was already replaced).. I would start with replacing the PPV. Then move onto the governor. Then check the unloader on the compressor.

This. I had mine do the same thing. It was the PPV.

 

[Oldworldtenacity]

Change the Air Govenor on the Air Compressor this controls the air drier and the amount that the air system builds

Yep, I forgot to mention I did that as well before changing the compressor out when I was troubleshooting.

 

[Oldworldtenacity]

Change the air dryer out. Suprman has the one you need for sale in the classifieds. He's very good to deal with.

Eric

Yep, Suprman is the one I got my new one from lol.

 

[Oldworldtenacity]

I wonder if your ppv is stuck then no air to governor and no air to compressor unloader from governor to stop making pressure and the same unloader air feed tells the air dryer to vent the expello valve on the bottom to dump moisture.

An OTR trucker mentioned this to me the other day and I didn't know if he really new what he was talking about, but after you and two other posters mentioning the PPV...I think it's time to change it out now.

 

[Oldworldtenacity]

Is this what I want to get?..................http://www.eriksmilitarysurplus.com/prprvaform9s.html

 

[Bandit02]

When my PPV stuck closed on me it built air to 150 psi and blew off at the compressor.

I think it's the governor, like mentioned above. The governor also sends pressure to the dryer so it can purge when the compressor cuts out.

 

[Bandit02]

You can get one waaaay cheaper at any truck shop/dealership. Bendix sells PPV's for about $15.

 

[Ford Mechanic]

My ppv stuck with the first cold snap, it built more air than normal and then made that sneeze noise on the passenger side of the truck.

 

[98G]

PPV for sure.....

 

[Ford Mechanic]

Does your air wipers work? Mine lost wipers running down the road in a rain storm also.

 

[Oldworldtenacity]

Does your air wipers work? Mine lost wipers running down the road in a rain storm also.

Yeah, they work fine. Have not had any issues with them yet....knock on wood.

 

[Oldworldtenacity]

So, I just got the PPV replaced today and the Air dryer still didn't sneeze after building up to 120PSI and setting there running for another 10 mins afterwards.

Also, now the ABS lights is on so I am afraid to take it out to see if the air dyer will cycle once I get out on the road.

I did put it in drive and the brakes seemed to be normal, but am unsure of what to do now with the ABS light staying on and am hesitant to take it out on the road. That light has never been on until after replacing the valve and starting the truck.

Not sure if its a coincidence or what as it seems like every time I replace a part a new issue arises.

 

[Bandit02]

Do you have air pressure from the governor with the purge line off? With 125 PSI the governor should send air to the unloader and the purge line on the dryer.

 

[Oldworldtenacity]

Do you have air pressure from the governor with the purge line off? With 125 PSI the governor should send air to the unloader and the purge line on the dryer.

Yes, I have pressure and it's a new Governor.

I'm going to let someone else sort out the air dryer issue...as this was my last shot at trying to get the air dryer to work. I am more concerned with the ABS light coming on after installing the new PPV valve now.

 

[SLOrazorsedge]

Yes sir! That's it :0)