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HWH Aux Compressor

July 12, 2015, 10:32:33 am

Hi Everyone.  We are looking for some advise.  We have a 2001 U320 and the aux compressor will no stop running.  It gets up to about 95 PSI and no higher.  It starting working funny after we went down a bumpy highway.  The motor runs great, I am wondering if the compressor side needs an over haul?  Any advise would be great.

Thanks,

Matthew

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Re: HWH Aux Compressor

Reply #1 – July 12, 2015, 10:54:49 am

Hi Rob here is a place to start your search.  HWH Aux Compressor Troubleshooting

If you use the search function on this web site you will find a bunch of postings and answers.

The Aux Compressor when parked can supply the slide air bladders, the HWH leveling system and your Zip Dee awning - if you have one.  You must find the leak and fix it.  When we had this problem some time ago we pulled the in line fuse to stop the compressor and installed a simple switch to turn the compressor off when required.  Got the switch at NAPA.

We considered this situation an opportunity to get to know our Ol Girl. 

You might need to rebuild/replace the Aux compressor but you probably have a leak some where.  The Aux compressor is built to cycle about 88K times.  There are threads that also will identify rebuild kits and how to do it.  For us a rebuild was not required.  Get a spray bottle with soap and water and start to spray the connections that you can see around the Aux. Comp. in your basement.  Chances are you will find the leak there and the repair is not too difficult.  Our leak was a fitting on the clear Desiccant canister attached to the air input hose.

Good luck.  The Search function is your friend. 

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Re: HWH Aux Compressor

Reply #2 – July 12, 2015, 10:56:26 am

If it gets to 95psi then it is not lokely that it needs an overhaul. Overhaul kits are available at zoro.com for under $100.  You may have a new leak or the pressure switch is stuck, check that first.  If you are going to buy a new pump consider the bigger pumps used in the 2002/2003 U320s.  About the same cost.

If you're anywhere Iowa, ever, make an appt at HWH (just off I80 about 40 miles from the Mississippi River).  They will look for leaks (everyone has some) and fix what needs to be fixed.  Great in-plant service and priced fairly.  We stop there just about every time we go by (every couple of years) for a heath and wellness checkup.

I wired a switch and a fuse into the 12v power to the pump. The 10 ga wiring runs up to the console to the left of the driver and the switch is in a blank panel spot.

Roger

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Re: HWH Aux Compressor

Reply #3 – July 12, 2015, 11:00:20 am

Hey Roger-

Looks like we are on the same page again.  We mounted our fuse on the support structure under the Aux. Comp. 

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Re: HWH Aux Compressor

Reply #4 – July 12, 2015, 11:07:48 am

Thanks for the advise.  We do have a dash switch I just cycle it twice a day and all is good.  The ZipDee awning does not like th slow pressure and needs an extra push to extend completely.  I will do some snooping around this afternoon.

Matthew

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Re: HWH Aux Compressor

Reply #5 – July 12, 2015, 11:11:37 am

We installed a 2nd small compressor to air our tires and also support the Zip Dee awning.  That's another story.  I believe the switch found on your left switch panel will fill your air tanks and does not control the on/off functioon of your Aux. Comp.  However, I could be wrong as Roger apparently installed a switch there to control this function. 

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Re: HWH Aux Compressor

Reply #6 – July 12, 2015, 11:42:38 am

The 2001 aux compressor pump wiring and sir plumbing is different from the following years.  No console switch from the factory. And the compressor does not fill the front and rear service tanks or the wet tank and does not feed the aux air line connection in the LP bay..  At least on mine. The aux compressor is a smaller one.

On the 2001 coach (at least mine) connecting an external compressor to the aux air connection in the LP bay will provide air to level or change height on the coach.  Good for working in it or it towing is required.  But it does not supply aire to the wet tank ot the service tanks so if your parking brake is set and you are out of air you have to mechanically release the brake.

Not everything is the same from year to year or even in the same year. 

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Re: HWH Aux Compressor

Reply #7 – July 12, 2015, 11:46:50 am

I stand corrected.   

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Re: HWH Aux Compressor

Reply #8 – July 12, 2015, 11:56:29 am

You will need a rebuild if you don't shut it off by pulling the fuse or fixing the leak, or both.
Don't ask me how I know.....

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Re: HWH Aux Compressor

Reply #9 – August 05, 2015, 04:01:57 pm

Hi Everyone.  I just wanted to give everyone an update.  I ordered the minor service kit for my compressor.  Installed the new seals on the piston and still not great.  Horrible vibration and rattling, slow to air up.  So I pulled the compressor right out and put in on my work bench.  The end of the shaft that attaches to the piston had a slight wiggle to it.  I used a pully puller to remove the piston, pretty easy.  As I wiggled the shaft I thought the bearing was shot so I opened the other end and pulled the centre shaft out.  Careful if you do this.  The magnets inside have a lot of pull.  Once the centre shaft was out I looked at the end and the bearing had worn down the shaft causing all my noise and poor performance.  I started looking for a new compressor and at $1500, I was getting that sick feeling.  So I ran the shaft up to the local machine shop and they rebuilt the shaft, put on 2 new bearings for only $200.  I put the unit back together and it purrs like a kitten.  I air up in half the time now.  So if you start getting a noisy compressor, check the shaft and bearing.  If all is good, these Thomas compressors literally have no vibration or noise.  I actually can't believe how quite they are.  Good for another 10 years I think.  Fingers crossed.

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