12 volt air compressor and slide alignment issue on 2004 U320

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12 volt air compressor and slide alignment issue on 2004 U320

May 27, 2020, 05:06:18 pm

I took my 2004 U320 on short trip to exercise it and get fuel. When I returned and deployed slide, I noticed 12 volt air compressor cycling on about every 15 minutes. I checked for air leaks, found none. I retracted slides and air compressor continues to cycle about every 15 minutes. As I inspected the retracted slides in the openings, I noticed the larger Living Room slide is not in the opening squarely. It is flush with the rest of the coach, but the vertical margins in the opening are off. The left side is noticeably wider, about ¾", and the right side is noticeably tighter, about 3/8". Until I can get coach into shop for troubleshooting, I am leaving slide retracted and the air compressor unplugged. My question is, can I drive the coach 12 hours with the 12 volt air compressor unplugged, or should I plug it in and let it cycle on and off and then unplug upon arrival?
Thanks to all in advance

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #1 – May 27, 2020, 07:46:31 pm

You can leave the compressor unplugged. The compressor from the engine should keep air to the slide seal.

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #2 – May 28, 2020, 08:32:55 am

This is the 03 air schematic. Your's may be slightly different. Assuming the check valves are working correctly and your system has not been modified the only source of air for the bladders is the HWH tank and the only place it gets air is from the HWH compressor..

I have added pressure gauges for the HWH tank and the bladder. With the compressor off the bladder seal holds the 12 psi it gets inflated to for months. The HWH tank stays above 70 psi for at least three weeks. The compressor cycling indicates a leak (not uncommon) but the low pressure bladder is probably OK for a day. Take a credit card and see it you can slip,it between the slide and the bladder, if not youe should be OK.

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #3 – May 28, 2020, 05:17:42 pm

Roger,
Thank you for the schematic. I do not believe the system has been modified in anyway. As for the check valves, is there a way to confirm they are working properly or am I better off replacing them? The 3/8 air line #75 is clearly marked in the bay at the compressor and per the schematic supplies the air for the slides. I do not see the check valves on the schematic.
Thanks again

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #4 – May 28, 2020, 08:22:08 pm

Check valves are hard to test without taking them out. And if you get that far I would just replace them. There are the pressure protection valves too. Mine were shot.

The check valves in the HWH lines are Haldex (Midland) KN23080.

The check valves on the tanks are Haldex KN23000
Amazon.com: Haldex KN23000 Check Valve: Automotive

Pressure protection valves are Haldex 90555399 Pressure Protection Valve 1/4" NPT , 65 PSI

Roger

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #5 – May 28, 2020, 08:55:29 pm

Quote from: cdm – May 27, 2020, 05:06:18 pm

Until I can get coach into shop for troubleshooting, I am leaving slide retracted and the air compressor unplugged.

Is your coach parked outside and how long before you go to a repair shop? If it is parked outside, then with the air compressor unplugged there is no way the bladder will stay inflated for long (unless that air system is leakproof) and rain can enter through the opening. But, if you have a new bladder since 2015 or '16 then it may very well default to 'sealed' in the absence of compressed air and you won't take on water.

Just something to consider.

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #6 – May 28, 2020, 09:31:12 pm

Quote from: Travelin' Man – May 28, 2020, 08:55:29 pm

Is your coach parked outside and how long before you go to a repair shop? If it is parked outside, then with the air compressor unplugged there is no way the bladder will stay inflated for long (unless that air system is leakproof) and rain can enter through the opening. But, if you have a new bladder since 2015 or '16 then it may very well default to 'sealed' in the absence of compressed air and you won't take on water.

Just something to consider.

I would guess anything under probably 8psi would leak.. possibly even 10psi.. I can attest to 3psi does for sure.

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #7 – May 28, 2020, 09:58:56 pm

Worst case, put blue tape over the gap.

Lots of reasons the HWH compressor will run that do not include the bladder.

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #8 – May 29, 2020, 05:12:45 am

The larger living room slide is deployed and is not passing the credit card test. The seal is tight after the compressor shuts down and the card will not slide between the coach and seal, but after a couple hours, with the compressor unplugged, the card will slide thru. I am losing air and will continue searching for where. I have blue tape over the gap now and weathered last nights rain just fine. When I have to make trip to service center, I will retract slide, then unplug compressor. If I encounter wet weather, I will plug the compressor back in if the blue tape peels away. I don't want to resort to duct tape and risk damage to the paint job

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #9 – May 29, 2020, 10:49:25 am

Near the compressor (in my 2003) is what is labelled in the schematic as the vacuum generator. Line 74 goes to it. The air line that goes from it to the slide is not shown in the schematic. In that line, directly above the vacuum generator should be a black manual valve. That valve, when closed, should isolate the bladder from the rest of the air system.

If that applies to your coach, you could run the compressor, then turn that valve to the Off position and unplug the compressor. If the bladder stays inflated, the leak is before that shutoff valve. Unless the valve itself is leaking (mine was) or the connection to the bladder is leaking.

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #10 – May 29, 2020, 06:33:07 pm

Thank you Ed,
On the flip side of that, if I shut off the valve after the compressor cycles, thereby isolating the slide, and the bladder still leaks down, I assume I can leave the valve closed and plug compressor back in, and it should no longer cycle more than normal. I have also determined that the leak is upstream of the valve. Is this correct?

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #11 – May 30, 2020, 12:51:32 am

That's right. Unless the valve itself is leaking. You can check that with soapy water.

I'm hoping to hear that the valve is not leaking and the bladder stays inflated with the valve closed. That would be a good start to the trouble shooting process.

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #12 – May 30, 2020, 07:20:51 am

I located what I believe to be the 2 vacuum generators Ed mentioned- see picture. Mine are on wall opposite compressor, to right of Inverter.
This morning I ran compressor until it shut off then I unplugged it.
The air lines going into the generators are not numbered so I shut off valve on the one on left just after compressor shut down.
I checked both slides with credit card and seals are tight.
When I return this afternoon, I will check both slides with credit card to determine if they are holding air and post results. Based on results, I may have to re-open valve on left vacuum generator and turn off valve on one on right, and run compressor again

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #13 – May 30, 2020, 08:38:39 am

Those valves are notorious for leaking around the stem past the packing nut. Check that area for your leaks and tighten the packing nut to seal it off. Do not be surprised that the stem won't turn once you stop the leak, this is the reason several have changed there valve out to a 1/4 turn valve that has "O" rings sealing off the stem.

Mike

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #14 – May 30, 2020, 10:12:53 am

CDM, I added a valve in the line from the slide bladder vacuum generator manifold to isolate the bladder. And a pressure gauge (0-30 psi) after that. I gan see what pressure is in the bladder and if the valve is closed if it leaks. We replaced (HWH did) our vacuum manifold because it was malfunctioning and not generating the necessary vacuum to deflate the slide. A rebuilt one from HWH with the same warranty as a new one was $250 including installation.

The manifold can leak as well as any of the air line fittings fittings to the HWH tank and then back to the compressor. The compressor comes on because the pressure switch sees pressure less than about 70 psi.

You should have a switch on the panel to the left of the driver that says something about HWH Tank Fill? It is not there in the 2001 setup so I am not sure of the label. This switch opens and closes a solenoid valve that sends air to the wet tank and From there to the front and rear service tanks. In general this should be off.

The HWH compressor also feeds air to HWH leveling manifolds which raise or lower one side or the other or the front or rear of the coach to keep the coach level. Anything the this part of the system can leak as well.

Small leaks are common. A no leaks at all system is probably less common.

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #15 – May 30, 2020, 11:28:19 am

Roger, I think the valve that CDM shows in his photo isolates the bladder.

My 2003 has the valve even though it's not shown in the schematic. I replaced it with a 1/4 turn valve when it was leaking.

Since my coach still has the original bladder I don't think the valve was added after the coach was built.

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #16 – May 30, 2020, 02:38:02 pm

The slide bladder on my 2001 is also original. We are very careful with it, always visually confirm that it has retracted before moving the slide. Keep all of the surfaces where the bladder makes contact as clean and polished as you can. Some are impossible to get at. I feel fortunate to have gone this long. But it holds pressure (11-12psi) for months.

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #17 – May 31, 2020, 07:41:38 am

Thank you for the input and advice. I like the idea of adding new valves and installing gauges.
I have determined which vacuum generator controls the living room slide. It is the one on the right in the picture. With both valves open, I let compressor run until it shut off, I then immediately shut off the valve controlling the living room bladder. The compressor has not cycled on over the past 16 hours, yet the Living Room Bladder does not pass the credit card test this morning. The Bedroom slide bladder does. The leak appears to be between the valve and the bladder, or the bladder itself. As best as one can, I have inspected the bladder when it was tight, and can not find any leaks. I am not sure what diagnostic action to take next. In meantime I plan on leaving compressor plugged in, the Living room vacuum generator valve closed, and blue tape over the opening

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #18 – May 31, 2020, 09:42:34 am

Behind the left front tire on my FT there's a spot where the hard line from the shut-off valve transitions to the soft rubber hose from the bladder. If I remember correctly there is a hose clamp there, and I had a leak there.

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #19 – May 31, 2020, 09:46:37 am

In the photo you posted, the airline leaving the valve appears to be at about a 45 degree angle from the valve. That could cause the compression fitting to leak. The next step would be to apply some soapy water to that fitting to see if it is leaking where the air line connects. Also get the threads of that connection wet to see if it leaks.

Edit: I just reread your post. It seems the line at the 45 degree angle is for the BR slide bladder. I would still do the same soapy water test on the connection from the valve on the right.

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #20 – May 31, 2020, 01:01:09 pm

CDM, have you sprayed a soapy solution around you LR bladder to check for a leak?

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #21 – June 01, 2020, 06:36:33 pm

Yes, I have sprayed soapy solution on the bladder when it is under pressure and do not see any signs of leakage. I am at point where I will let the service people take over. I will leave the air to the bladder shut off at the valve at the vacuum generator. I do appreciate everyone's input

Re: 12 volt air compressor and slide alignment issue on 2004 U320

Reply #22 – June 01, 2020, 10:30:13 pm

Quote from: cdm – June 01, 2020, 06:36:33 pm

I will leave the air to the bladder shut off at the valve at the vacuum generator.

Be aware - if you have extended the slide and shut off the 1/4 turn valve to its bladder, you will not be able to retract the slide. That valve needs to be open (on a 2003) to satisfy the vacuum sense that "trips the bit" that allows the slide to be moved. To retract the slide you will need to clamp the slide line shut with something like vice grips then open that valve and allow the vacuum generator to cycle. Then close the valve again once the slide is fully in.

And yes, the 1/4 turn OEM valves are notorious for leaking and brass quarter turn replacements are recommended.

To drive with a bad slide bladder, we like round closed cell insulation tubing (aka backer rod) to fill the gap and low-tack duct tape covering over the gap.

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