Air Dryer for an M35A2

[The King Machine]

I'll take some photos of mine later. It works without issue.

Mine looks to be set up the same as in your diagram

 

[rustystud]

For your application that diagram is OK. There should be one line from the governor to the air-compressors "unloader valves". The "T" connection on your system is just confusing the compressor with another pressure source.

 

[m-35tom]

i think the diagram is correct. that is exactly the way mine is. the control valve on firewall now has dual purpose. 1 to put pressure to compressor un-loader valves to stop pumping air. 2 to signal air dryer to cycle and vent air first in a burst then in slow manner to expel all water. you could have several problems. first unhook and plug or cap the 1/4 line going to the bottom of dryer. does air system work ok now? if yes the control valve in dryer is leaking. if no then probably control valve is bad.

but i am not using an AD9 i am using system from a UD box truck

 

[rustystud]

i think the diagram is correct. that is exactly the way mine is. the control valve on firewall now has dual purpose. 1 to put pressure to compressor un-loader valves to stop pumping air. 2 to signal air dryer to cycle and vent air first in a burst then in slow manner to expel all water. you could have several problems. first unhook and plug or cap the 1/4 line going to the bottom of dryer. does air system work ok now? if yes the control valve in dryer is leaking. if no then probably control valve is bad.

Are you using a Bendix AD9 ? The way the AD9 works is to send a separate signal (pressure) to the governor to let it know to stop the compressor and allow the system to purge. There are several ways to do this, but the most simple and best for our application is to use the AD9 signal pressure to stop the air-compressor. Haldex uses its own system, so if your using the Haldex then go by their diagrams. My system works great, and it's installed just like our buses. Or just do what you want.

 

[m-35tom]

OK i thought maybe that dryer sent signal to compressor to unload. i see it does not. it works exactly like mine, only accepts pressure to cycle. so that diagram is correct for yours and mine.

 

[Valence]

Thank you guys for your help and input here.

So Mr. Rusty, here's a picture of my governor again, where I've labeled the connections connections 1-4:

#1 & 2 are Tee'd together, I haven't followed where this line goes, but I'm pretty sure it comes directly from the second air tank.
#3 Goes to the air dryer Control
#4 Goes to the engine air compressor unloader


So what you're saying is to remove #1 & 2 from the governor and cap off/replace that Tee, move #3 up to where #1 & 2 were, and return #4 to be the only connection on the bottom?

 

[m-35tom]

you cannot make any kind of decision just guessing!! you need to know exactly where 3 and 4 go.

 

[Valence]

I know exactly where 3 and 4 go. But I'll go look for #1 & 2 - but one can realize that it won't affect #1 and 2 if you bypass the governor. They'd still be connected to each other, which wouldn't affect wherever the lines come from and wherever they go.

Also, I still don't understand why the way I have it plumped is incorrect. I took the figure (Figure 11, page 12) directly from the "AD9 Installation" instruction PDF.

http://beamalarm.com/foretravel-links/PDF/air_dryer_ad-9_installation.pdf

Also attached here: 3.14MB
View attachment air_dryer_ad-9_installation.pdf


I'm not arguing with anyone, I'm just trying to get an understanding here why it is claimed that the instructions are wrong in this application on an M35A2.

 

[m-35tom]

For your application that diagram is wrong. There should be one line from the governor to the air-compressors "unloader valves". The "T" connection is just confusing the compressor with another pressure source.

why does the other small line not go to the control port on the AD9? i looked it up and that is what is called for, pressure on control port when compressor is shut off to tell the dryer to purge. that pressure stays there until governor on firewall removes pressure on unloader. of course if that 'other' small line goes anywhere else = problem!! also the AD9 could be bad. remove small line from control port, there should be no pressure from port ever. only from line going to port.

 

[Valence]

why does the other small line not go to the control port on the AD9? i looked it up and that is what is called for, pressure on control port when compressor is shut off to tell the dryer to purge. that pressure stays there until governor on firewall removes pressure on unloader. of course if that 'other' small line goes anywhere else = problem!!

The #3 connection (1/4" black poly line), I have added, and it only goes directly to the Control port on the AD9. Yes, the AD9 could have a problem - always a possibility, but it was brand new when I bought it last year.

remove small line from control port, there should be no pressure from port ever. only from line going to port.

I shall try this. Thank you.

 

[Valence]

also the AD9 could be bad. remove small line from control port, there should be no pressure from port ever. only from line going to port.

I ran the truck with the 1/4" nylon control line from the governor disconnected at the air dryer as pictured above. When the shut-off pressure was reached, a strong blast of air came from the governor not the AD-9. Nothing came from the AD-9 control port.

When the nylon line started to vent, I jumped up and turn off the truck. Air continued to vent from the governor, maybe for 10 seconds, then it stopped. Below is a picture of the air pressure gauge after this happened.



During this, the AD-9 did not purge/vent.

 

[m-35tom]

sounds completely normal to me. plug the line not the AD9 and test again. you will have to vent the air somewhere else to trigger the governor, it should turn on compressor near 90 and then turn it off near 120.

that looks like a wrong gauge to me since normal is 90 to 120 gauge should read higher.

note the pressures the governor turns compressor on and off.

 

[rustystud]

View attachment Scan0201.pdf
Use this diagram and you will be OK. I don't know how your connected to the governor.
The diagram you posted in Post# 140 is correct. I was thinking about your "T" connection when I posted earlier.