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Topic: Governor/Air Drier issue? (Read 945 times) previous topic - next topic

Governor/Air Drier issue?

I replaced the D2 governor last Fall since while cruising, the upper end of air pressure was usually at about 110psi. It still went to 120 when loading and I consistently heard the air drier 'pop off' at that point. The readings were the same with the new governor, so I figured that I must have a slow leak, but the HWH leveling works well with only about 15psi drop in about 24 hours  - so 'normal' leakage.
Driving to a new campsite a couple of days ago (about an hour driving) I noticed a strange thing. It appeared as if the governor was now doing its job and top pressure was consistently 120psi when driving.  It would reset to that new resting place after braking.
While idling and waiting my turn to check in at the campground, I heard a new sound.  Instead of the usual air drier pop off, I was getting a longer venting, about four times longer and occurring about every 30 seconds.
My first course of action will be to dial back the governor about 1/4 turn to reduce the 'unload' point to see what difference this makes. The mystery remains as to why the governor spontaneously started resting at the higher point.  Perhaps the locking nut on the governor adjustment stud came loose and it vibrated in that direction?
The discharge from the air drier is dry and there does not appear to be any desiccant discharge along with the air.

Ideas?
Woody & Sandy Lloyd
1993 Grand Villa
Unihome U280
Cummins / Allison
Build # 4379

Re: Governor/Air Drier issue?

Reply #1 –
When was the last time the air dryer was serviced, was the bottom end repair kit #DQ 6020 installed, if not that could be your problem.
The selected media item is not currently available.Bill&Doris 97 U270 36'
University of Parris Island Class of 66
Semper Fi  Build# 5174 MC#17094

Re: Governor/Air Drier issue?

Reply #2 –
Quote from: Mike_Sandra_Lloyd –
I replaced the D2 governor last Fall since while cruising, the upper end of air pressure was usually at about 110psi. It still went to 120 when loading and I consistently heard the air drier 'pop off' at that point. ............................

Ideas?
Mike,
If you are saying that the compressor loads to 120 psig and then immediately falls to 110 psig (when the compressor unloads), where it tends to stay much of the time you are driving, then definitely,  (+)1, what Bill said.
Generally, though, erratic behavior in compressor load and unload pressures is strictly D2, Bendix governor driven.  Also, if the D2 does not unload (shift) cleanly and abruptly, the blowdown of the tower may not sound the same (may be drawn out or delayed).  But, it can also be that the spool in the dryer tower is gummy (or otherwise lethargic) and is not shifting cleanly and abruptly
Shifting the upper end "unload" setting may change things up a bit, but I would have both a new D2 and a lower end rebuild kit on standby.  Even though your D2 changeout is not that old, stranger things have happened than a new D2 being marginal or having a nagging defect.
HTH,
Neal
The selected media item is not currently available.
Neal (& Brenda) Pillsbury
'02 U320 SPEC, 4200, DGFE, Build #5984
'04 Gold Wing
'07 Featherlite 24'
'14 Jeep Grand Cherokee Summit
MC #14494
Exeter, NH & LaBelle FL
Quality makes the Heart Soar long after Price is Forgotten

Re: Governor/Air Drier issue?

Reply #3 –
Since our ownership of this beast is less than two years old, and the previous owner is not available to answer that question - I suspect that the bottom end repair kit needs to be acquired.  A D2 is easy to get. and is a cheap thing to have as a spare.
The thing is that the first 'toot' that signals that the governor has gone into unload mode is the usual short pfft., what follows are a sequence of longer releases (about 4-5 seconds long) at about 30 second intervals.
I will get the bits and bobs, do my reading on how-to, and report back.  I am assuming that there is not a problem with me driving while this is going on.  I think I will replace the governor first and see what effect that has.
Woody & Sandy Lloyd
1993 Grand Villa
Unihome U280
Cummins / Allison
Build # 4379

Re: Governor/Air Drier issue?

Reply #4 –
When you dial back the governor both the high and low will move, same when raising, usually a 30 psi. spread.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Governor/Air Drier issue?

Reply #5 –
My understanding is that when the air pressure reaches 120psi, the governor goes into 'unload' mode and this initiates the air drier purge. Since after that event, I am getting a series of longer purges, then that leads me to suspect the governor or even the compressor (which may not be responding to the 'unload') as supposedly directed by the governor.
Woody & Sandy Lloyd
1993 Grand Villa
Unihome U280
Cummins / Allison
Build # 4379

Re: Governor/Air Drier issue?

Reply #6 –
There is a air line coming off the air compressor that periodically needs to be cleaned of "coked up oil",this can be found in the
8.3 service manual and may be part of your problem.Also,if your going to rebuild the bottom half of the drier you might as well
get a rebuilt one or rebuild the whole thing so your starting from zero.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Governor/Air Drier issue?

Reply #7 –
Mike,

Before you go and by a bunch of parts you can't use check and see what dryer you have. Being a '93 you may have an AD9 rather than a Pure Air Plus which is what the DQ-6020 fits, but won't do you any good if you have the AD9.

Mike 2
Pamela & Mike 97 U 320

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

Re: Governor/Air Drier issue?

Reply #8 –
Sounds like your dryer either needs a rebuild or replacement.  I think you will find the purge valve on the dryer to be gunked up with grease and oil / dirt which makes the purge erratic and slow.  You can get a rebuilt dryer at NAPA and the cost is about $100 more than the repair kit. 
Current coach 1996 U320 40'
Previous coach, 1990 36' U280
 

Re: Governor/Air Drier issue?

Reply #9 –
The conclusion: enroute to have the starter replaced (and having to drive down big hills in big city morning rush hour) all sorts of crises began... first of all I noticed that the air gauges (rear, in particular) were dropping into the 70-80 level, while the front stayed in the 90-100 psi range. So... lots of downshifting and use of the PacBrake and avoiding the brakes.  At the bottom of a long hill with five lanes of traffic converging into three and about to cross a major bridge in tight traffic -- the alarm sounded for extremely low air pressure! The choice was to stop immediately or go a bit further. Deciding to go a bit further (and not use the brakes) the alarm went off as i headed for the apex of the bridge - and stayed off (thankfully for my already elevated heart rate and blood pressure!!) as I proceeded down the Trans Canada Highway through Vancouver BC for another 30 kilometers at 70-80 km/hr. until I reached the Cummins repair site. They replaced the starter, but could not fix my air leak since it was not attached to a Cummins compressor (!).
Anyway a mechanic shop was located and the air hose / leak was fixed (it was the large-diameter supply hose from compressor to air dryer that had been rubbing against a metal support ring - that at one point probably had a rubber grommet to protect hoses, but not anymore) and the airdryer was replaced.  What came off appeared to be an AD4, and what went on was an AD9 remanufactured Bendix. The wee beastie ran better than has in the past two years of our ownership (air pressure-wise).
I have no idea how long it has been since the air dryer was serviced - does sit being an AD4 provide a clue?
Anyway the re-manufactured air dryer was $496. CDN and the core 'buy-back' was $234 CDN - so a pretty good deal as far as I am concerned.
Now on to the next problem(s) - whatever they may be. Still very happy with our tiny home on wheels!
Woody & Sandy Lloyd
1993 Grand Villa
Unihome U280
Cummins / Allison
Build # 4379