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Gurus,

I was minding my own business when a fellow guru commented to me his concern regarding the length of time it took my coach to build air.  My coach has always taken several minutes to build up to 120 psi from a low air pressure situation.  That simple conversation caused me to learn about my air system and to make some needed repairs.  Take what I am going to tell you with a grain of salt.  I really don't know what I am talking about and am putting this out there to cause you to think about your own coach and how its air system works.

Before I go into the details of what I found and what I did, I would like to jump to the bottom line things that I learned....

• The governor is critical to the overall health of your air system.  They are cheap and easy to replace and in my opinion are often overlooked.
  
• If you are not building air quickly, a simple and small leak can stop you on the side of the road leading to an expensive tow or worse.
  
• Everyone knows that you should change the cartridge in your dryer regularly, but it is important to test the dryer to see if it is leaking air.
  
• Finally, because of the conversation with the fellow Guru, I now know much more about my air system and with the same Guru's help, I now build air quickly and my engine air system works as designed.
  

When I first looked at my engine service brake air system on my coach, it would take 5-6 minutes at high idle to go from 0 psi on the engine gauge to 120 psi.  At that point the system would "pop-off" and tell me that I was full of air.  I thought this was normal.  Well it *might* be normal if your air bags are fully deflated.  In my case with the bags at travel height and 70-80 psi in the system it would still take a while to reach 120 psi.  Something was definitely amiss.

I had another weird symptom as well.  Instead of a nice PSFT! when the dryer popped off, I would sometimes get a psst-psft-psft-psft-psft-psft sound.  In other words it had a series of small pop-offs instead a single purge.  Hmmmm.

Time to do some learning!   

The main components of the engine air system are the Compressor, the Governor and the Air Dryer.  Of course there are other parts, but these are the stars of the show.   

The compressor makes air, the air goes thru the dryer and onto the service tank where it is used to operate the brakes.
   

The compressor is bolted to the engine and is turning whenever the engine is running.   It is cooled with engine coolant.  It obviously produces compressed air.   The dryer obviously dries the compressed air.  But the smarts of the whole system is the crazy little device called a governor.

   

The governor is the widget that tells the compressor whether to be making air or to be idling.   The compressor has an unloader circuit that allows it to turn easily without the energy required to make air.   This  unloader circuit is controlled by an airline from the governor.   The way that the governor determines when to unload the compressor is by using an airline from the service tank to measure pressure in the system.  The governor uses pressure from the service tank along with its cutoff pressure adjustment to determine when to send air to the unloader on the compressor -- essentially turning off the compressor.    At the same time it sends an air signal to the air dryer to tell the dryer to purge any liquid.   This is what is happening when you hear the "pop-off".

   

Consultation with the other Guru, led me down a path of testing and repair in the order of cheapest / easiest  to harder and more expensive.    In order of lowest expense and complexity are the governor, the dryer and the compressor.

The first thing I did was to replace the governor. 
This drastically improved the amount of time it took to fill the service tank...but the pop-off was still not working correctly.

The next thing was to order a new air dryer  We raised coach and blocked the coach frame as well as chocking the wheels..  The dryer is bolted to the wall just behind the tag axle on the drivers side.   Access the bolts in the cable reel bay.  I used an air wrench.    It took maybe 30 minutes to change the dryer.  (The new dryer came with a new desiccant cartridge).  

Here is old dryer.
   

At this point, the system was going from 0 psi to 120 psi in about 1.5 minutes.   (bags already full).  Success!  We found that the purge valve on the old dryer was rattling and had worn to the place where pieces were loose within the valve assembly.  

Since my coach has 250,000 miles and 16 years of use, I would say that I got my money's worth from the governor AND the dryer.  

If we had found that we were not making enough air, we would have looked at the compressor next....but luck shined on me and my compressor was fine.

I said it above, and I will repeat here.  Your coach may be different and I may or may not be right about the way that I think about the air system.  What is absolutely true is that the air system is critical to the operation of the coach and that it would be a good idea to do a once over your system so you understand how it works.   Do yourself a favor and find your governor and buy a spare.  They are fairly inexpensive and it may be the one thing that gets you going again when you run out of air.

Thanks again to the unnamed guru who assisted on this project.   It really does take a village.

Cheers,
bill

If anyone is considering adding a bunk bed, this might be an option worth considering.
 

This is yet another thread on the subject of replacing your auxiliary air compressor.  I didn't find all the answers I was looking for in the existing threads so I am adding this one.   Please see other threads in this forum with titles:
110 compressor
Jun-air
120v air compressor replacement

I think I replaced the original Jun-Air Model 6 that had been running faithfully for untold hours since 1999.  Mine was mounted with the generator.  This provided a location within the sound absorbing structure of the genny enclosure.  Between my lousy hearing and the very quiet JunAir I never heard a thing!  I had to install an hour meter in the front right side bay with the pressure switch just to monitor its operation.  I would check the meter and if it only slowed a few minutes a day, I knew all was well.

Then, the hours took a huge jump and I knew the free ride was over.  A quick check of the exit pressure on the JunAir confirmed its demise.  Due to my remote location for the winter I chose not to tear it apart and try a repair.  Besides, it had served me well and deserved retirement.

I was a little shocked when I started looking for a replacement.  Turns out JunAirs are expensive.  There was discussion here about going with an inexpensive Chinese compressor going by the model number MP75 and sold very reasonably by California Air Tools.  My emails and PM's to a member who had planned to do that conversion went unanswered, so I was left wondering what happened.
Tom always finds these fantastic eBay deals and had found a JunAir for cheap that way.
In the end I bought a new JunAir OF332 delivered to by door for the grand total of $412.28.   While not a McCloud deal, I think I did alright.

Jun-Air has an internet presence and I was able to find manuals and schematics online, but nothing exactly for the OF332.  Another member had mentioned confusion on how to connect this model.  I received the compressor with one side of a 9 pin connector.  It contained 8 wires coming from the compressor.  After digging through the documentation and ringing out the wires here is what you need to know.  The black and white wires just go directly to the hour meter.  I had no use for that meter, so removed it and the wiring.  Of the remaining wires, you just need to know the correct three of interest - Hot, Neutral, and Ground.  Connect as follows:   Hot to Brown, Neutral to Blue, and Ground to Green/Yellow.  Remember, almost nothing you can do with 120vac is going to hurt a 220/120V motor.
The compressor has two stages - clearly marked low and high.  I had to do the plumbing.   Output of low to input of high.  Be careful with your purchase and use of fittings.  Some threads are not tapered and require fittings with "o" rings to seal.  The press on tube type appears to be for 10mm OD, so had to order that.

I have attached some pics of the completed installation.  This is an oil-less rocking piston pump rated for continuous use.  I fully expect it to last as long a I have the coach.
Russ

Hello All,
Anyone looking for a Jackknife couch?  Found this on CL in case anyone is interested.....https://minneapolis.craigslist.org/csw/fuo/d/monticello-jacknife-couch/7023473880.html

Steve

Do you check the slide hydraulic tank with the slides open?  Closed? or some combination of the two?

I noticed the roof vent on my bus has no flap to close the vent, I am not sure if it never did or it was broken at some point in time.  I would like to make what I have function as I like the vintage look of it and the fact that it is all aluminum on the exterior.  My vent has 3-T's stamped into the aluminum housing.   I will try to upload a picture.  Are there parts available to restore or convert this vent so it can be closed?

So I know this is probably another dumb question but when traveling to visit family with no room to park the bus on their property I noticed a school close by.  Has anyone ever parked at a school on the weekend when school is out?  

I know I could park the bus elsewhere and drive a car to them but the convenience of parking within walking distance is preferred.

Hello,
We are looking at a 1991 45' Newell with the 8V92 Detroit Diesel and 160,000 miles.  I was wondering if 
anyone can give me some pros and cons?  Thank you for reading

my wife and I are the proud “new” owners of #566, a 2000 45 foot Newell with 3 slides.
Pam has already joined and become a junior guru.....so now is my turn.  Happy to be a part of Newll Gurus and look forward to learning a lot!!

Hey guys, I have a issue with might front right side height.  I parked at a campground in Yuma, level spot, and I noticed my front right side was very high. The left side and the rear was all at travel height. Does anyone have any idea what will cause this.  I can use my auto leveling system and it works fine. When I start the engine to air up, the right side front goes fully extended and the rest of the coach is fine. Any help would be greatly appreciated. Thanks John  1998 Newell coach 472