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

[Oldworldtenacity]

Well, I started the truck today and the ABS light went off within 5 seconds and apparently it was the batteries being a little low as fellow member Swampdonkey informed me could cause that issue with the light. I guess it really was a coincidence in this case.

Also, I took the truck out on the road today and the air dryer started working.

However, now instead of the PPV valve releasing air every 12 seconds after you go over 20mph....now the Air dryer is releasing air every 12 seconds even while sitting still at low idle....plus now the truck builds air all the way up to 150 PSI in both of the primary and secondary tanks and stays there even as the air dryer sneezes aevery 12 seconds.

Before the install of the new PPV valve it would not build air past 120PSI and the air dryer would not sneeze.....the PPV valve would release air every 12 seconds, but not until you went over 20mph.

I am totally perplexed now by this issue,....but hey...at least my air dryer works now LOL.

 

[98G]

The PPV doesn't release air like the air dryer does.

If you're hitting 150psi, most likely what is releasing is the pressure relief valve. Usually this means the PPV isn't letting air go to the secondary systems, which includes the unloader.

 

[Oldworldtenacity]

The PPV doesn't release air like the air dryer does.

If you're hitting 150psi, most likely what is releasing is the pressure relief valve. Usually this means the PPV isn't letting air go to the secondary systems, which includes the unloader.

Yep, you are right..I meant the pressure relief valve was releasing air before. THe air is now coming from the air dryer oddly though...I checked it....and I can feel the air coming from the air dryer expello valve. I'm baffled big time.

I mean, why would it now build air to 150 PSI from just replacing the PPV valve??

 

[Bandit02]

My truck last winter did that. Built air to 150 psi and it blew off at the compressor. Turned out to be the PPV because the governor wan't getting any air pressure to put the compressor into unloading AND send a signal to purge the dryer.

All the PPV does is keeps air in your brake side of the system first (until you build 60 psi) so you can release the brakes before using any accessories (wipers, horn, etc). But the governor is tied into the accessory circuit as well.

You put a new dryer on. Are you sure the air lines going to it are in the right spots? If the dryer is purging alot like you say usually that means there a leak in the purge line going to the dryer.

 

[Oldworldtenacity]

My truck last winter did that. Built air to 150 psi and it blew off at the compressor. Turned out to be the PPV because the governor wan't getting any air pressure to put the compressor into unloading AND send a signal to purge the dryer.

All the PPV does is keeps air in your brake side of the system first (until you build 60 psi) so you can release the brakes before using any accessories (wipers, horn, etc). But the governor is tied into the accessory circuit as well.

You put a new dryer on. Are you sure the air lines going to it are in the right spots? If the dryer is purging alot like you say usually that means there a leak in the purge line going to the dryer.

Supposedly the lines are in the correct places because I even had a certified heavy truck mechanic who installed my Transmission back in January look at it and he said everything looked like it was hooked up correctly.

 

[Bandit02]

Does your wipers, horn work now?

 

[Oldworldtenacity]

Does your wipers, horn work now?

Oh yeah, they have always worked great.

 

[Bandit02]

New air dryer, new PPV, new governor. It purges every 20 seconds and the compressor builds to 150 psi. Hmmm

If that was my truck I'd start suspecting the compressor isn't being put into the unloading stage. That would explain it building to 150 psi and there's nothing stopping it from pumping to tank.

I kinda think your unloader is stuck closed. (Or a sufficient leak from the governor to the unloader keeping it from unloading, soap & water would find that quickly).

 

[Oldworldtenacity]

New air dryer, new PPV, new governor. It purges every 20 seconds and the compressor builds to 150 psi. Hmmm

If that was my truck I'd start suspecting the compressor isn't being put into the unloading stage. That would explain it building to 150 psi and there's nothing stopping it from pumping to tank.

I kinda think your unloader is stuck closed. (Or a sufficient leak from the governor to the unloader keeping it from unloading, soap & water would find that quickly).

It's definitely a tough one to figure out for sure

One thing I should have mentioned earlier is that after installing the new PPV.... the air dryer didn't even start sneezing until after I drove it around for about 30 mins.

It also didn't start building up to 150 from 120 until the air dryer started purging every 12 seconds.....and the that was only after I had drove it around and then stopped at the gas station did it start doing the above.

It did the same thing with the old compressor as well as the new one regarding the build up to 120 with the air dryer not sneezing until after you went past 20mph and then preceding to release air via the pressure relief valve every 20 second....so changing the compressor to a new one didn't change that at all...and now that I've changed the PPV it is doing the 150 build up with the actual air dryer sneezing every 12 secs deal...and not until after driving it for 30 mins.

Gee, I bet I sound crazy in this thread now lol

I think I'm probably just going to have to take it to an air systems expert at my local Cummins dealer or something.

 

[Oldworldtenacity]

I strarted the truck today and it will only build to 120 PSI now after sitting overnight and the air dryer will not sneeze now.

Also, there is a steady stream of air coming out of the bottom of the air dryer now...I think maybe it's the expello valve.

Here is a pic

 

[Bandit02]

if you have all new components from one end to the other then something isn't plumbed right. Hard to know not being with it not in front of us.

 

[Suprman]

The unloader air "signal" from the governor to the air compressor unloader is the same signal that tells the expello valve to purge. Check and see if there is constant air flow from this line this could cause the compressor not to make proper pressure and also cause the expello valve to stay partially open.