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Topic: AD-9 air dryer, electrical question (Read 403 times) previous topic - next topic

AD-9 air dryer, electrical question

my air dryer gave up the ghost and I am currently in the middle of replacing it at an Airbnb. My old one just had a single wire going to a stud and must've grounded to chassis. the AD9 that I'm putting in has a two pin plug (see pic). does it matter which one is hot and which one is ground? It's just heating an element right? So I'm thinking not but want to confirm.
1987 Grand Villa ORED
2001 U320 4010

Not all that wander are lost... but I often am.

Re: AD-9 air dryer, electrical question

Reply #1 –
My guess is it doesn't matter.  Yes just a heater.
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: AD-9 air dryer, electrical question

Reply #2 –
Ground one wire . There may be a color. That is green, black , white. ? May be intended for ground. May not matter. Use a fused test lead to verify that it's not also grounded to the body.

Re: AD-9 air dryer, electrical question

Reply #3 –
Thanks guys. It didn't come with a wiring harness but I managed to find one for a headlight bulb that fits.  I guess I can get it in there and check for continuity through chassis to confirm it doesn't ground that way and then assume either pin can be hot. Fingers crossed it's not any more complex than that
1987 Grand Villa ORED
2001 U320 4010

Not all that wander are lost... but I often am.

Re: AD-9 air dryer, electrical question

Reply #4 –
Quote from: Elliott –
It didn't come with a wiring harness but I managed to find one for a headlight bulb that fits.
Not surprisingly, this subject has come up before....

How to update Bendix AD4 to AD9 on 91 GV U300

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: AD-9 air dryer, electrical question

Reply #5 –
Hmmm. Got the new one put back in, but I'm not hearing it purge once the coach gets up to full pressure. Everything else is working like expected, with good clean air coming out of my tanks when I drain them. it builds up to 130 psi and then stops, which is the top end of the governors range like expected but no purge sound from the drier. Thoughts?

Edit: The air governor is new. Put it on back in May.
1987 Grand Villa ORED
2001 U320 4010

Not all that wander are lost... but I often am.

Re: AD-9 air dryer, electrical question

Reply #6 –
Elliott,

If your air compressor is cutting out at the correct time/pressure, then the D2 governor is working properly.  In that case, the "no purge" problem must be someplace in the control line between the air compressor and the dryer.  See the AD9 tech document linked below.

You could disconnect the control line from the control port on the dryer.  Then start your engine and reduce the pressure in the air system (fan the brake pedal) so the air compressor cuts on.  Go back to the engine bay and hold your finger over the open end of the control line so you can feel what happens when the air compressor cuts out.  At the same time the compressor cuts out you should feel pressure coming out of the control line open end.  This pressure signal is what tells the air dryer to purge.

If you DON'T feel pressure when the compressor cuts out, then the control air line must be blocked or crimped or something ??

If you DO feel pressure when the compressor cuts out, then there may be something obstructing free air flow into the dryer control port, or possibly you got a bad rebuilt dryer.

AD9 Service Data

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: AD-9 air dryer, electrical question

Reply #7 –
Quote from: Chuck & Jeannie –
Elliott,

If your air compressor is cutting out at the correct time/pressure, then the D2 governor is working properly.  In that case, the "no purge" problem must be someplace in the control line between the air compressor and the dryer.  See the diagram linked below.

You could disconnect the control line from the control port on the dryer.  Then start your engine and reduce the pressure in the air system (fan the brake pedal) so the air compressor cuts on.  Go back to the engine bay and hold your finger over the open end of the control line so you can feel what happens when the air compressor cuts out.  At the same time the compressor cuts out you should feel pressure coming out of the control line open end.  This pressure signal is what tells the air dryer to purge.

If you DON'T feel pressure when the compressor cuts out, then the control air line must be blocked or crimped or something ??

If you DO feel pressure when the compressor cuts out, then there may be something obstructing free air flow into the dryer control port, or possibly you got a bad rebuilt dryer.

https://www.anythingtruck.com/instructions/060-AD9ServiceDataSheet.pdf
Chuck any idea how much pressure should be coming out of the control port on the governor? There's air coming out of it but not much. It'd have to be a pretty weak spring in the drier to be activated by such little pressure
1987 Grand Villa ORED
2001 U320 4010

Not all that wander are lost... but I often am.

Re: AD-9 air dryer, electrical question

Reply #8 –
Quote from: Elliott –
Chuck any idea how much pressure should be coming out of the control port on the governor?
Logically, I would say you should have the same pressure out that port as you have in the wet tank, because that is where the pressure originates.  So, about 130 psi?

Where is your D2 located?  Is it mounted on a frame member, or is it attached directly to the engine air compressor?

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: AD-9 air dryer, electrical question

Reply #9 –
Quote from: Chuck & Jeannie –
Logically, I would say you should have the same pressure out that port as you have in the wet tank, because that is where the pressure originates.  So, about 130 psi?

Where is your D2 located?  Is it mounted on a frame member, or is it attached directly to the engine air compressor?
It's mounted directly to the air compressor and I think I found the problem. I pulled it off and realized there's no gasket on it! So air is leaking out where the governor meets the compressor and that is probably the reason for the low air pressure at the end of the control line. Not sure how I pulled that one off because I've installed a few of these and never made that mistake before. Of course, I figured this out 20 minutes after the Truck part store closes for the weekend and I need to move on Sunday  :-X
1987 Grand Villa ORED
2001 U320 4010

Not all that wander are lost... but I often am.

Re: AD-9 air dryer, electrical question

Reply #10 –
Yes, that is most likely the problem.

Back in the day, every mechanic tool box contained a few sheets of "bulk" gasket material.  If you needed a missing gasket, you could simply cut one out of the sheet.  I still have several sheets of that stuff lying around.  Of course, it is probably petrified by now.

Don't suppose you have any more spare D2 governors (including the gasket) in your parts stash....

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: AD-9 air dryer, electrical question

Reply #11 –
Quote from: Chuck & Jeannie –
Yes, that is most likely the problem.

Back in the day, every mechanic tool box contained a few sheets of "bulk" gasket material.  If you needed a missing gasket, you could simply cut one out of the sheet.  I still have several sheets of that stuff lying around.  Of course, it is probably petrified by now.

Don't suppose you have any more spare D2 governors (including the gasket) in your parts stash....
I do not :-( but the Walmart in town has rtv gasket maker
1987 Grand Villa ORED
2001 U320 4010

Not all that wander are lost... but I often am.

Re: AD-9 air dryer, electrical question

Reply #12 –
In a pinch you can cut one out of the cardboard (last page) of a legal pad. If you have a can of spray paint handy give the gasket a coat of spray paint and let dry before installing.

Miike

Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: AD-9 air dryer, electrical question

Reply #13 –
Quote from: Elliott –
I do not :-( but the Walmart in town has rtv gasket maker
Just use that stuff sparingly - a VERY thin coat.  Don't want errant little broken-off pieces of RTV circulating through your air system.

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"
 

Re: AD-9 air dryer, electrical question

Reply #14 –
The ltv did the trick and it's cycling like i'd expect now  ^.^d thanks for the help guys
1987 Grand Villa ORED
2001 U320 4010

Not all that wander are lost... but I often am.