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Topic: Air system (Read 725 times) previous topic - next topic

Air system

This morning I was dumping and all of a sudden, the pop off valve on the air system started going off about every 10 seconds.  I went in the bay and un-plugged this black thin cylinder and it quit.  Next thing I know the coach is un-level big time and it would not re-level, so plugged it back in and it seems to be working now.  Did get the coach to re-level, thank goodness, as we are on a pretty good slope. Can anyone tell me what that thing is I unplugged?  I am assuming it has something to do with the HWH system, but why did it start to blow off pop off valve and now it seems okay?  UGH!


In the first photo, you can see the where I unplugged the black disconnect.  In the second is the pop off valve.
Joe & Dottie Allen
Sold!  December 2023.      2000 U320; build # 5645
Our coach " Maxine"
Motorcade #  15922;  Escapee 150950; FMCA F330833; Boondockers Welcome;  Harvest Hosts;  Thousand Trails
'98 U320 from 2000-'06
USAF '62-'66

"Do not spoil what you have by desiring what you have not; remember that what you now have was once among the things you only hoped for." ―Epicurus

Re: Air system

Reply #1 –

Joe, the pressure switch (gray Square D thing) is what turns the pump on based on pressure.  Mine sticks on occasion. with power off to the pump you could try spraying the contacts with an electronics contact cleaner.  A new one is about $25.  I carry a spare.

Looks like this one, I will go look for the actual part number.

Square D by Schneider Electric 9013FHG2J27 Air-Compressor Pressure Switch,...

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Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Air system

Reply #2 –
Quote from: Roger & Susan in Home2 –
Joe, the pressure switch (gray Square D thing) is what turns the pump on based on pressure.  Mine sticks on occasion. with power off to the pump you could try spraying the contacts with an electronics contact cleaner.  A new one is about $25.  I carry a spare.

Looks like this one, I will go look for the actual part number.

Square D by Schneider Electric 9013FHG2J27 Air-Compressor Pressure Switch,...

Thanks Roger, that is not in the photo above but I saw it when laying on my back in the bay!  However, now, the pump is coming on about every 45 minutes.  It did this when we first got the coach and then it settled down to about once in 2 or 3 hours, sometimes more.  I can't find any leaks and you would think it had to be a good one for it to do that.  The pressure gauges on the dash go down to about 70 and then the pump starts until it shuts off around 110 or there about.
Would that pressure switch cause the initial problem with the pop off valve and not installing any air to the system?
As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.
Joe & Dottie Allen
Sold!  December 2023.      2000 U320; build # 5645
Our coach " Maxine"
Motorcade #  15922;  Escapee 150950; FMCA F330833; Boondockers Welcome;  Harvest Hosts;  Thousand Trails
'98 U320 from 2000-'06
USAF '62-'66

"Do not spoil what you have by desiring what you have not; remember that what you now have was once among the things you only hoped for." ―Epicurus

Re: Air system

Reply #3 –
As I understand the air system in a late 2000 and early 2001 coach (like mine) is that when ignition is off the small compressor feeds the HWH tank and the bladder manifold (if you have them) and the front and rear leveling manifolds.  The front and rear service tanks are isolated from the aux compressor supplied air by check valves.  The only air that gets to the service tanks is supplied by the engine driven compressor through the air dryer and the wet tank.

Your service tanks will vary in pressure while driving from about 90 psi to 110-120 psi.  They may not read the same. when you stop driving and shut the engine off they may lose pressure but because of the pressure protection valves they shouldn't get below about 65 psi.  If there are leaks in the PPV or in the front or rear brake air systems that can eventually go to 0.

While you are driving air from the service tanks is used to maintain ride height.  When you stop and the level system is on air from the service tanks (down to 65 psi) or from the small aux compressor is used to add air to level the coach.  In automatic mode the preference is to let air out before adding air.  If the aux compressor has power and the pressure switch senses low pressure the compressor will come on until the pressure is restored.

If the air system is connected as the plan shows the aux compressor will never add air to the service tanks and should not change your air pressure gauges.  If the gauges are changing then you likely have failing or failed check valves or pressure protection valves.

This air schematic applies to build number 5871 and later.  Yours may be different.  If so it is worth checking to see if you have the one for your coach or get one.  It is pretty hard to make your air system correct if you do not know what correct is.

In this air configuration ...
If you connect an external compressor that can supply dry air to the Aux Air Connection it will supply air to the leveling manifolds to let you adjust level or raise the coach or return to ride height without running the engine. This air should be dry. If all of your check valves are working correctly this will not add air to the service tanks.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Air system

Reply #4 –
Roger, I will take a look at the schematics tomorrow as my build was pre 5871.  The two gauges on the dash are definitely loosing air and when they get to around 70, the pump kicks in.  So, you are saying I may have a failing check valve or valves?

Appreciate all your expertise and you have been a big help many times.  Thank you again!
Joe & Dottie Allen
Sold!  December 2023.      2000 U320; build # 5645
Our coach " Maxine"
Motorcade #  15922;  Escapee 150950; FMCA F330833; Boondockers Welcome;  Harvest Hosts;  Thousand Trails
'98 U320 from 2000-'06
USAF '62-'66

"Do not spoil what you have by desiring what you have not; remember that what you now have was once among the things you only hoped for." ―Epicurus
 

Re: Air system

Reply #5 –
Well, I know I have 2 bad pressure protection valves.  My check valves may be OK because aux air input does what I expect, raises the coach and does not add air to the service tanks..

A thorough test is a good thing.  Check valves have to get removed to test.  My summer project.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN