HWH Compressor Fix

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HWH Compressor Fix

June 26, 2010, 10:15:41 am

In our 1997 U295, the HWH 12V compressor would run, but would not raise the coach. HWH leveling worked fine with air pressure from the brake system.

After a lot of crawling in and out of the bay, listening, looking, and feeling for air flow, I found air coming from a port at the bottom of what appears to be a moisture trap on the 12V compressor module. It appears that there is a moisture drain valve on the trap that is controlled by a solenoid. I managed to pull the solenoid assembly without removing the entire compressor assembly. The pin, spring, and chamber, that comprise the valve were fouled by precipitate from the moisture from the trap. I rinsed the pin and spring in the sink with RO water. I used a Q-Tip and RO water to clean out the chamber, which remained attached by wires to the compressor module. The precipitate was easy to remove.

I reassembled the solenoid and fired up the leveling system. Air no longer leaked from the moisture purge valve. The electric compressor raised to rear of the coach several inches and leveled the coach. Yea!!!

Re: HWH Compressor Fix

Reply #1 – June 26, 2010, 11:05:51 am

Steve will have to comment later, but this has been a recurring problem on our coach. We replaced the valve in 2007 due to corrosion, and have yet another replacement solenoid valve enroute from MOT now, 3 years later. It was an extremely rainy 2009, especially in Maine where we were for 5 months, and I wonder if that contributed to the problem.

It's not an inexpensive part, so his plan is to see if there's any way to repair/rebuild and carry the old one as a spare.

Michelle

Re: HWH Compressor Fix

Reply #2 – June 26, 2010, 12:20:06 pm

Michelle,

Thanks for the quick feedback. We are so new to Foretravel (April 2010) that we haven't taken a "big" trip yet. I've been tweaking up systems in anticipation of a 3,500+- mile journey starting in about July 6. I had not seen any posts regarding the issues with the HWH compressor. I observed symptoms and started trying to isolate the problem.

Ours is a lightly used 1997 U295 model that has spent the bulk of its existence in an airplane hangar near Bellville, TX. Bellville is in the transition zone from the very humid Gulf Coast of Texas, and the dryer Texas Hill Country.

I found no evidence of corrosion in the valve on our coach. The materials appeared to be brass, stainless steel, or chrome plated. Our problem was strictly due to an accumulation of a white precipitate that dissolved quickly in pure (RO) water. It looked like the junk inhibited the sliding pin from properly moving to a closed position. Cleaning the valve was easy. Assessing the problem and getting valve in hand was challenging.

The outlet port on the drain is a long brass nut. Perhaps a plastic hose could be fitted to the open end of the nut to allow an occasional shot of cleansing water, or perhaps even a little light lubricant, to be injected into the valve. If the end of the plastic tube were accessible from the bay, maintenance could be performed with the contortions required to get to the compressor. Such a modification would be a kludge that was increase the problems, but it also might help. Perhaps someone with specific expertise might be able to suggest improvements.

Re: HWH Compressor Fix

Reply #3 – June 26, 2010, 01:28:19 pm

So how do you use the brake system air to air up the HWH system?

George

Re: HWH Compressor Fix

Reply #4 – June 26, 2010, 02:23:15 pm

My experience has been that when the pressure on the brake system is "up" (> 70 psi), I can control the attitude of the coach with the the HWH control panel. That includes raising, lowering, or leveling the coach. As long as there was sufficient pressure supplied by the brake system, the HWH worked fine. That was true even when the 12V HWH compressor was not delivering air to the HWH system because of the stuck (open) moisture purge valve.

While the 12V compressor was not working properly, I could not raise any part of the coach with HWH after the pressure in the brake system, as indicated by the gauges on the dashboard, dropped below about 70 psi. If I started the engine and brought the pressure up in the brake system, the HWH leveling would work.

I infer that the air suspension system will use air FROM the brake system if the pressure is high enough, but will not supply air TO the brake system. If the 12V compressor is working properly, it will maintain enough pressure to keep the suspension system inflated. The air system diagram in my owners' manual is consistent with my inference.

Re: HWH Compressor Fix

Reply #5 – June 26, 2010, 02:53:29 pm

Quote from: George Hatfield – June 26, 2010, 01:28:19 pm

So how do you use the brake system air to air up the HWH system?

George

He is talking about using the coach air to refill the system so that when it checks level every thirty mins it will have a reserve of air to raise a side of the coach if needed.

Re: HWH Compressor Fix

Reply #6 – December 28, 2012, 12:09:32 pm

Resurrecting an old thread here. My HWH is exhibiting similar issues. It'll level off the coach air fine but won't budge off the aux compressor. I can here the aux compressor come on to try and level but just runs continually and nothing "levels".

Dave, where did u discover the issue? Was it on the compressor or somewhere else?

Re: HWH Compressor Fix

Reply #7 – December 28, 2012, 12:38:34 pm

We find our small HWH compressor takes FOREVER to raise the heavy rear and almost forever to raise the front. It seems just to be way too small for the job, so we never use it. Later coach years have much larger air compressors.

We level with engine running or lots of air in tanks and then shut the HWH panel and it stays level.

HWH compressor in our coach only comes on when air tank pressure is low and HWH system is calling for raise. Compressor does not fill coach air tanks.

Re: HWH Compressor Fix

Reply #8 – December 28, 2012, 01:33:33 pm

I agree with Barry regarding the inadequacy of the 12VDC compressor in '96, '97. A couple of times I have pulled the compressor and cleaned a purge valve at the bottom of the condensate bowl. It gets fowled with a with residue that keeps the valve from closing properly. It that valve leaks, the compressor won't supply any pressure. Our compressor is behind the inverter/converter in a cubby in the center of the coach. The cubby is accessible via the big bay on a 36' coach. Some details of how I cleaned the valve are earlier in this thread.

Re: HWH Compressor Fix

Reply #9 – December 28, 2012, 02:19:48 pm

Thanks Dave. I guess I misinterpreted your statement when you called the compressor a module. My compressor is easily recognizeable in the first bay on the driver side.

Best Regards,
Benjie

Benjie Zeller
(512) 587-4628

Re: HWH Compressor Fix

Reply #10 – December 28, 2012, 03:49:54 pm

The compressor in my 1996 U320 WTFE 40 is in the compartment just rear of the driver side front tire. It produced compressed air but did not build more than 5 psi because the fitting at the bottom of the water seperator bowl was split. I used a brass fitting which was the correct diameter and made a replacement which fixed the leak. The pressure would not stop building at this point because the on/off pressure valve was plugged. It is a good quality pressure valve which I dismantled and soaked in vinegar for several hours. I used tooth picks to remove all dirt and it works very well now. It does take a few minutes to see any rise in the rear bags. I installed scrader valves on the air lines to the airbags so that I can use my (120 VAC) shop compressor to raise the coach. The pressure required in the front bags is 45psi while the rear bags require 75 psi.

I replaced all airbags and installed a 1/2 inch thick high impact plastic spacer at the top of each airbag. Now I find a level spot and just dump all the air in the airbags, which means coach stays level reasting on the bumpers inside the airbags. My coach can move without adding air to airbags because the tires no longer press against the underside of the floor when the air is dumped.

Re: HWH Compressor Fix

Reply #11 – December 28, 2012, 07:59:41 pm

Wyatt, that's a good idea. Does that extra half inch make any difference to anything when the air bags are at full extension?

Re: HWH Compressor Fix

Reply #12 – December 28, 2012, 08:25:47 pm

Quote from: P. Wyatt Sabourin – December 28, 2012, 03:49:54 pm

I replaced all airbags and installed a 1/2 inch thick high impact plastic spacer at the top of each airbag.

pictures please, pretty please

Re: HWH Compressor Fix

Reply #13 – December 29, 2012, 01:06:45 pm

I am in Canada for Christmas right now but will return to my Foretravel on Jan 3rd. I will post pictures then.

With the 1/2 inch spacers at the top of the airbags, I have not noticed any difference when driving. I did not adjust the air ride valves so coach is at the same height when in "travel mode". The only difference is that an airbag would bottom out on the rubber bumper inside the airbag a 1/2 inch sooner when hitting an abrupt rise in the road. Previously, it could have bottomed out on the metal donuts, metal to metal, which can cause damage.

With the airbags at full entension and the coach a 1/2 inch higher then ever before, there is less clearance in the suspension components, but nothing is binding, and there has been no frightening noises. My biggest concern was the drive shaft coming apart. I have seen that with radical 4x4 trucks.

I plan to study the driveline and steering bar angles and perhaps raise the "travel mode" 1/2 inch by adjusting the air ride valves. Our coaches ride low, which is great for handling, however, not so great when negotiating uneven driveways. I have experienced damage scrapping the front bumper or rear trailer hitch in rustic campgrounds.

Re: HWH Compressor Fix

Reply #14 – December 29, 2012, 01:34:37 pm

Thanks for great resolution to my useless 12VDC compressor problem. Two years ago I finally disconnected it, stopped trying to "fix" and now dump when going to be parked for more than two days, using 2x8s to level the parking site if needed. The "bumpers" are a great fix for allowing movement. Andy1

Re: HWH Compressor Fix

Reply #15 – December 29, 2012, 01:59:39 pm

I'm having a little trouble locating the compressor on my 1997 U295. Any help would be great.
Terry

Re: HWH Compressor Fix

Reply #16 – December 29, 2012, 03:34:48 pm

If coach is 36' long, open big bay, extend joey bed, climb into bay, use square drive to remove four screws from panel covering a cubby toward front of coach, look behind the Heart Freedom 25 in the cubby.

Re: HWH Compressor Fix

Reply #17 – December 30, 2012, 12:16:23 am

I'm going to take a pic tomorrow and post. I don't have a glass bowl anywhere visible. Hoping maybe someone can point me in the right direction or maybe its hidden. I may need to remove my compressor to do any maintenance given how it is positioned.

Re: HWH Compressor Fix

Reply #18 – December 30, 2012, 12:52:59 am

I did one repair with the compressor in place. The next time I took it loose from the floor and gained better access. I did not disconnect the air lines or electric lines.

Re: HWH Compressor Fix

Reply #19 – December 30, 2012, 09:01:16 am

HWH compressor didn't have glass bowl until slides were introduced.

Re: HWH Compressor Fix

Reply #20 – December 30, 2012, 09:12:56 am

Seems like this compressor is somewhat finicky and expensive. Mine works but is very weak. Has anyone replaced with standard 12v tire inflator type compressors? Seems like 1 or 2 of those blowing through a dessicant canister and a standard pressure switch would do the trick. Would probably need to enclose them in some soundproofing.

When you pull the actual compressor out of one of these tire inflators they are tiny but potent.

Chuck

Re: HWH Compressor Fix

Reply #21 – December 30, 2012, 10:35:47 am

I do not ave a glass bowl and I have two slides.

Re: HWH Compressor Fix

Reply #22 – December 30, 2012, 12:11:38 pm

Quote from: John S – December 30, 2012, 10:35:47 am

I do not ave a glass bowl and I have two slides.

Last time we looked at the newest coaches, they didn't have the condensate or desiccant bowls anymore, either.

Re: HWH Compressor Fix

Reply #23 – December 30, 2012, 02:47:01 pm

Michelle:
You meant NO condensate or dessiccant for the auxilliary 12 volt compressor, but that the engine compressor does still have dessiccant, correct?

John S:
My 1996 U320 auxilliary 12volt compressor does have a clear condensate plastic (see-through) bowl.

Replacement 12v compressor:
The low cost 12v compressors are not intended for long time service and will not last very long.

The 12v compressors that Foretravel installs cost hundreds of dollars and are very high quality. If your compressor does not build pressure, look for leaks because even a small leak near the compressor will cause low pressure. Also check the intake air cleaner for restrictions. If not those things, then remove the head to check the valves. Even a tiny item under a valve will cause low pressure.

Re: HWH Compressor Fix

Reply #24 – December 30, 2012, 03:02:43 pm

Quote from: P. Wyatt Sabourin – December 30, 2012, 02:47:01 pm

Michelle:
You meant NO condensate or dessiccant for the auxilliary 12 volt compressor, but that the engine compressor does still have dessiccant, correct?

Wyatt,

Correct - I was talking about the 12V aux compressor, not the engine one. Thanks for asking for clarification.

Steve's actually interested if finding out why it's not on the newer coaches. Certainly for the amount of air pumped with the aux compressor the amount of desiccant in that little bowl seems quite small (further evidenced by how often one has to replace/regenerate it). The extra bowls, connections, etc. do complicate the aux compressor set-up. If it's been found not to be needed (or not enough "bang for the proverbial buck"), eliminating it sure would be a nice simplification.

Michelle

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