After reading the HWH Air Leveling Systems Text book for my 680 series, I understand that the compressor will turn on when the rear pressure switch detects pressure below 60psi. Fine. But why? My coach is level... I have all the air dumped and the HWH control panel shows red lights in all four corners (level). The compressor still turns on occasionally and I don't understand why, since on my 01 the compressor ONLY feeds the bags (via manifold) and HWH tank. What's it attempting to do when turning the aux pump on if it's not leveling the coach?
Somewhere in your AUX system you are losing air. The pressure in the system drops below 60 and the pressure switch calls for air turning on your compressor. Pressure switch doesn't know or care why system loss pressure (from use or from leakage), so it will on/off as it's designed to do at the open/close pressures. A spray bottle with some soapy water can help identify where you are losing air. I would start at the AUX manifold misting all threaded connections and then work your way forward. An air leak will present as bubbles from the soap in the water.
I know I have leaks, I've been chasing and fixing them for over a year now. I just don't understand the design... why try to build pressure at the rear six pack if it's not getting used anywhere? I suspect the leak is at the pressure switch itself since I've rebuilt the rest of it (six pack o-rings, plungers, compression fittings at six pack AND bags, as well as new bags).
The aux compressor is delivering air to the six pack and then it's not getting used since all the solenoids on the manifold are closed currently. Seems like a design flaw
I have the same problem with AUX compressor cycling with no use from the systems it serves. I am installing an on/off switch at the dash to interrupt the pressure switch so the compressor doesn't keep cycling due to leaks. Probably spend less time on it if I just fixed the leaks!
I can't agree that it is a design flaw, the compressor and switch are doing their jobs. If the system had no leaks, the compressor wouldn't be cycling. Compressor nor pressure switch care why or how the pressure in the system was used or lost, their job is just to maintain pressure.
I have my air compressor on a switch in the bathroom so it's not an issue, I'm asking out of curiosity mostly. I guess if it weren't leaking at the pressure switch, low pressure would mean one of the solenoids is open and calling for air, so that makes sense. I guess it's time to go replace that pressure switch incase we aren't level and want to use auto-level mode.
My auxiliary compressor runs normally (about 3 minutes) most of the time. However, occasionally it will keep running until I shut it down with a switch I added. I now suspect the pressure switch at the compressor. Spraying the mechanism with WD-40 has not been helpful for any mechanical / friction hang-ups. Contacts of the relay are not pitted. Apparently, they are cheaply made and can cause problems.
Next, I am going to replace the pressure switch...keeping my fingers crossed. Any other suggestions? Jim
2002 U320
Elliott, I'm not sure how much different your 680 system is than my 2000 system, but a few things will make the compressor run. #1 is the pressure switch. Mine was set for 65psi - on, 85psi off. Anytime the HWH system calls to "raise" the compressor will run.
On my system, there are 3 x 3/8 hoses coming off the air manifold. Lines 57, 75 and 76.
Line 76 has a solenoid that opens when the AIR TANK button is pressed, and allows air from the HWH system to the Wet Tank. With the switch off, this solenoid is closed and does not do anything.
Line 75 goes to the bladder seal air tank. It's always open (no check valves), so what is in that tank is what is at the pressure switch.
Line 57 goes through a check valve and to two of the brake tanks and to the HWH manifolds. The check valve on this line keeps wet tank pressure from coming back into the HWH system, but if you have leaks here, as that system loses air, the HWH system will continue to share pressure until it gets to the turn on pressure of your pressure switch. I suppose you could put an on-off valve on this line so you could manually stop the HWH system from providing air to the brake tanks and manifolds when you don't want it to.
Your system may be different. Do you have the schematic from the manual?
Jim, checkout page MI40.020A of the HWH textbook. There is only two ways to turn on the aux pump... a 12v source from the control panel or from the pressure switch on the rear six pack. That power feeds into a relay. Perhaps your relay is sticking?
https://www.foreforums.com/index.php?action=media;sa=media;in=1458
I do.
We don't have a feed to our wet tank from the aux compressor on the 01s but line 75 and 57 are the same. The diagram shows a check valve between the manifolds and compressor as well as between the slide tank and compressor. Both the pressure switch and those check valves are easy to get to so I think it's probably best to just replace them all instead of playing whack a mole...
I've already replaced the Line 57 check valve as it was open when I got the coach last year. This year, I also found the Line 76 check valve at the wet tank to be open and replaced it as well. Seems like fairly cheap insurance.
Agreed. I've also learned that if I'm going to touch anything on the air system I should just replace it. Once valves are turned or fittings removed for the first time in 20 years, they're almost never air tight again afterwards.
My compressor has exactly the opposite situation. It NEVER comes on. Even when the air pressure on gages goes below 60 psi. My bags just keep loosing air slowly until reaches the stops, resting on the tires. Suggestions?
The pressure at the tanks won't cause the aux pump to turn on. The pressure switch we're talking about is at the rear six pack and measures pressure in a loop that's normally completely closed off because the solenoids are all closed.
Your issue sounds like either: 1) the computer doesn't know you're out of level and isn't sending the 12v signal to the compressor or 2) it's sending the 12v but it's not getting their. The first thing I'd do is confirm that you're getting battery power at the HWH control box. Page MI40.015A in the link I shared with Jim shows you where power enters the box depending on which box you have. Hopefully it's just a fuse.
Edit: also, you're in "auto-level" mode right? And not manual level mode? You need to press the level button twice to get into auto-level mode. If not, the computer isn't going to do anything
The pressure switch that controls compressor is at the compressor manifold on my 2000 U320, not at the rear 6 pack. Just as a heads up for others.
Elliot I have a question, you say that you have red lights at all 4 corners so the coach is level. Do you turn the HWH system off or leave it turned on?
My coach is one of the ones where the HWH control panel is only on if the ignition is on. So I put it in auto level, let it level, and then turn the ignition off.
I'm assuming Elliott's system (680) is different than mine (and yours Evantwheeler), as mine was also on the compressor manifold. You can see it in the first picture, with the gray plastic cover. Picture two shows it with the cover off.
I'd be interested to hear if any other 2000s are configured similarly, I'm thinking your system has been modified. From what I can tell, you should have a 600 or 680 series, and the original configuration for those is with the pressure switch on the six pack.
Maybe someone retrofitted it to be more like the 2000 series. Or maybe you have a 2000 series ¯\_(ツ)_/¯.
Reading that document page, especially the last paragraph, doesn't mention anything about controlling the pump.
Elliot if when the coach is level can you turn off the HWH and then see if it will stay level and how the pump operates then. It might give you a different outcome by not running.
Do you have a slide?
I saw your pressure switch at the compressor manifold in another photo you posted. I'll find it and post it here.
In this picture from your other thread on compressor switch, the pressure switch that commands compressor on is behind the grey plastic cover with the Square D text on it, upper right hand corner behind the air line.
(https://www.foreforums.com/index.php?action=dlattach;topic=43352.0;attach=115033;image)
Aux Compressor Switch (inside) (https://www.foreforums.com/index.php?topic=43352.msg436206#msg436206)
Thanks, didn't know that and I have a new place to hunt for leaks. The HWH textbook does indeed show a compressor switch in the schematics for both compressor configurations, but doesn't clearly describe which of the two switches actually turns the compressor on. How do you know it commands the compressor on, have you fiddled with it?
Makes me wonder what the pressure switch on the six pack is used for. Same purpose but different air supply (brake tank) ?
The pressure switches on the six packs talk to the brain. The pressure switch at the manifold is strictly for the aux compressor function. The brain can call for compressor on independent of the aux compressor pressure switch. The aux compressor pressure switch can also call for compressor on without any call for air from the brain. Two totally separate systems as far as the controls which work in parallel. The aux pressure switch and the brain do no communicate with one another.
This text below is from page 11 of 22 from the HWH leveling manual that you posted in regards to compressors for levelling:
"Air compressor assemblies consist of several components.
There is the 12 volt compressor and a relay to control voltage
to the compressor.
The pressure switch on the compressor
assembly controls signal voltage to the relay. There is a
water trap with a normally open 12 volt air solenoid. This
solenoid will close whenever the compressor is running. The
two output compressor has a second normally open air
solenoid. This valve closes whenever there is a +12 volt signal
from the leveling system control box to run the compressor.
Anytime a raise function-automatic, manual up arrow or the
"RAISE" button - is being used, a +12 volt signal is sent to
the compressor from the control box. This turns a single
output compressor on if air pressure in the system is below
approximately 105 psi. A +12 volt signal from the control box
will turn a two output compressor on at anytime.
A +12 volt
signal through the auxillary pressure switch for auxillary air
will turn the compressor on if system air pressure drops below
60 psi."
The easiest way for me to describe how they are independent controls is how the compressor works when operating the slide. When you turn the key on for slide operation, the brain calls for compressor ON, regardless of system pressure. This is a parallel control system to the aux compressor pressure switch. As long as the key is on for slide operation, the compressor is running. Once you turn key OFF, the compressor will continue to run until it hits the upper pressure limit of the aux compressor switch and then compressor will shut off.