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Topic: Auxiliary Air pressure pump activation (Read 1317 times) previous topic - next topic

Auxiliary Air pressure pump activation

Just a continuation of a previous post a few months ago.  Finally got around to resuming my project of checking all the fittings I could see at the air tanks below and could hear nor found no leaks using soapy water spray.  Remain  concerned why the pump doesn't shut off automatically.    I did install a 12v disconnect switch keep it from burning itself up.  All the air pressure systems seem to operate OK..ie brakes, leveling,  slide out.  The active dash air pressure gauges peg at about 110psi and upon shut down eventually go down to ~52psi or so.    Worked with Roger Engdahl who was very helpful to facilitate the removal of the pump from the coach and after checking over everything I could,  problem remained.   

What is the location of that which signals the Aux pump to shut off or turn on ?
Fiddler
1959 Parris Island grad
40' 2001 U320 Build 5875
1999 Suburban K1500 toad
1986 Corvette Pacecar
ssoftail@comcast.net

Re: Auxiliary Air pressure pump activation

Reply #1 –
On my 03 there is a Square D pressure switch located near the compressor.  It thought it had a problem when my compressor would not shut off but I later found a leak in the front slide bladder.
Bill and Joyce, The House2 and Dashboard Pig III
2000 U320 4210 CAI (The House2)
Build # 5733
2019 F150 King Ranch FX4

Re: Auxiliary Air pressure pump activation

Reply #2 –
The "Square D" pressure switch noted in Bill's post is what tells the pump to turn on and off.  It is exactly like the switch that controls my water well pump.  It is adjustable for "cut-in" and "cut-out" pressure.  There should be instructions on the underside of the removable gray plastic cover.

If your aux pump operates like my (older) system, the HWH "brain" calls for aux pump operation based on a signal from one or more pressure switches.  On my coach, the pressure switch is mounted on the rear HWH manifold.  The request for aux pump operation sends power to the "Square D" control box on your pump.  If the "Square D" control sees line pressure less than "cut in" pressure, it forwards the power to the pump motor, telling it to run.  Once line pressure exceeds "cut-out" pressure, the "Square D" control box cuts power to the pump.

Perhaps the "Square D" control on your pump is never seeing "cut-out" pressure?  See craneman's post below for possible causes.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Auxiliary Air pressure pump activation

Reply #3 –
There must be a leak, or the compressor is not making the required pressure due to a compressor issue. If the cutoff switch was the problem there would be a high pressure problem. I am not familiar with the exact compressor you have but similar ones I have repaired with this symptom had broken reeds or unloader valves causing it.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Auxiliary Air pressure pump activation

Reply #4 –
Just a note about the Square D pressure switch. I ordered a replacement from Amazon using the same complete model number from the existing one. When it arrived the preset pressures were not the same. I found the correct part to be a Square D fixed pressure switch that was available from the pump manufacturer.  May be available elsewhere, just saying be sure even though same model #, double check for correct pressure settings.
Bill and Joyce, The House2 and Dashboard Pig III
2000 U320 4210 CAI (The House2)
Build # 5733
2019 F150 King Ranch FX4

Re: Auxiliary Air pressure pump activation

Reply #5 –
Easy to plumb in a pressure gauge (got my parts for about $20 at Napa in St. Petersburg) Then you can read the cut in and out pressure right on the line and adjust right there
Tim Fiedler    2025 LTV Unity MBL on Order
2000 Chevy Tracker 2 Door Convertible 4WD Now lifted 4.5"
1985 Citroen 2CV6 Charleston
Murphy Rebel on wheels with 175HP Titan
Cessna P337
1980 48' Westport MY (!/4 Share)

Re: Auxiliary Air pressure pump activation

Reply #6 –
Hi Fiddler,

Presuming you have all these components on yours DC compressor...could it be a leaky discharge solenoid? Put your finger on the bottom of the desiccant bowl's line to see if you have air escaping when pressurized - a common problem. That definitely would keep the compressor running.almost continuously. The output is supposed to be closed when compressing and open up to drain off head pressure when the compressor shuts down.

Your desiccant bowel also could be leaking - look for cracks in the plastic. Lots of other leaks could  be your problem as well.
Jim Frerichs
2002 U320 42'

Re: Auxiliary Air pressure pump activation

Reply #7 –
Discovered slide bladder losing air overnight;  in particular the front and rear top corners showed daylight.  Turned on the Aux pump and it succeeded to inflate and seal the corners.  The next morning, same thing;  this time I started the engine and the bladder inflated and sealed OK.  The next morning same loss of air to the slide bladder. What area is most suspect to check to track down the leak?

BTW,  where is the square D pressure switch?  What does it look like?
Fiddler
1959 Parris Island grad
40' 2001 U320 Build 5875
1999 Suburban K1500 toad
1986 Corvette Pacecar
ssoftail@comcast.net

Re: Auxiliary Air pressure pump activation

Reply #8 –
My shutoff valve for the bladder had a leak.  You might try that.  I just had to turn it a little to get it in a no leak position.

Rich
Rich and Peggy Bowman
2002 U270 3610 WTFS, build #5939--"Freedom"
2022 Jeep Grand Cherokee Summit 4xe
SMI AirForceOne brake system
PakCanoe 15

Re: Auxiliary Air pressure pump activation

Reply #9 –
Quote from: Fiddler –
BTW,  where is the square D pressure switch?  What does it look like?
It's right there in your pump photos...  It has a gray plastic cover held on by a single acorn nut.  Big "D" enclosed in a "square" embossed on it.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Auxiliary Air pressure pump activation

Reply #10 –
Quote from: Rich Bowman –
My shutoff valve for the bladder had a leak.  You might try that.  I just had to turn it a little to get it in a no leak position.

Rich
We too found the problem to be the 1/4 turn HWH slide valves. We have three slides, and found that two were leaking. This fixed our problem. When I called Mike at FOT, he mentioned that they had shipped out valves to several  other folks. Ours are mounted on the forward wall as you're looking at the aux. pump.
 
Byron
Byron and Linda Betncourt
2006 Phenix 40'
Buda,TX

Re: Auxiliary Air pressure pump activation

Reply #11 –
That common leak problem, posted before that mine leaked and MOT put in a new design.

Found it out by turn off aux compressor, monitored the psi at the compressor, it continued slowly fall and with slide bladder out of the picture was narrowed to either third tank or valve or fittings.  Bubble soap showed very slow at the cutoff valve so ditto Byron

Mike
Mike
2001 U320 4010 Build 5878 (Gus)
Wrangle Unlimited Toad
Nacogdoches

Re: Auxiliary Air pressure pump activation

Reply #12 –
Quote from: Byron Betncourt –
We too found the problem to be the 1/4 turn HWH slide valves. We have three slides, and found that two were leaking. This fixed our problem. When I called Mike at FOT, he mentioned that they had shipped out valves to several  other folks. Ours are mounted on the forward wall as you're looking at the aux. pump.
 
Byron

Don't forget that those 1/4 turn shut-off valves can be repaired easily with just two new O-rings.

Re: Auxiliary Air pressure pump activation

Reply #13 –
Could'nt figure out how to resume my last reply on the aux pump running issue.  Nonetheless, here's an update.  I did rebuild the bladder shut off valve and it quit leaking.  I did discover that the bladder seal was not leaking,  I was hearing the aux pump running in the partially open bay door and thought it was coming from the bladder on the lower rear corner.  I sprayed soapy water on the entire perimeter of the slide and found no bubbles.  Today,  I poked around under the coach starting with the air tank just aft of the generator and found most tanks had pressure gauges installed and read 60psi with no leaks except one.  I sprayed the two valves just to the rear of the drop down step and voila; the valve to the left of the step (facing it) was leaking.  Both valves BTW had pressure gauges installed;  the leaking valve read 40psi and the other 60psi like the rest.  The leak was coming from the top of the collar of a black plastic gizmo just under the pressure gauge.  I tried to turn the collar with no luck;  then turned the round fluted part below it and a bunch of rust came out the hole at the bottom.  I guess the black gizmo that is leaking needs to be replaced but a little uneasy on how to remove it and where to get the replacement.  Comment?

I took some pics with my cell phone but cannot figure out how to unload them to this forum.  I'll take them again tomorrow with a real camera and post em. 
Fiddler
1959 Parris Island grad
40' 2001 U320 Build 5875
1999 Suburban K1500 toad
1986 Corvette Pacecar
ssoftail@comcast.net

Re: Auxiliary Air pressure pump activation

Reply #14 –
Replaced both air pressure regulators behind the drop down step.  A word of caution to those you may have to do the same.  Be very careful when you replace the regulators to ensure that they are installed in the exact way the old ones were.  That is,  check the direction of the air flow arrow imprinted on the body and compare the old and new location of the outlet plug.  I did not and once complete it was blasting air out of the top of both regulator adjustment knobs;  and couldn't figure out why.  When I returned home,  did some rewarding inquiries on the internet when it became obvious that one of 2 of the outlets for the gauge is plugged;  in my case the wrong one was plugged and thus the problem.  I had to dismantle the whole thing and move the plug on both to the opposite side,  reinstalled and then success;  no more leaking there.  However,  after repairing the leaking shut off valve for the aux compressor and now repairing these leaking regulators; upon turning the aux pump on for over 30 minutes,  it still continued to run.  The only way I could get it to quit running was if I turned off the shut off valve; then,  after about 10 min or so the pump would shut off.  Not sure where to go from here....perhaps,  back to the RV and continue the search for leaks.  Also, while under the coach I sprayed soapy water every suspect air fitting I could see with no leaks apparent.
BTW, ran across an old  article written in the Motorcader by Jack Bradshaw FOT tech that alerted to the step regulators a common area for leakage problems.  Look forward to any comments that might help.  In the meantime,  the aux pump will remain shut down until the issue is resolved.
Fiddler
1959 Parris Island grad
40' 2001 U320 Build 5875
1999 Suburban K1500 toad
1986 Corvette Pacecar
ssoftail@comcast.net

Re: Auxiliary Air pressure pump activation

Reply #15 –
Sorry to probably repeat a suggestion and something you have tried.....but if the shut off to the bladder stops thing and having it open causes the continuous running.....do I have that right?.....sounds like a leak in the bladder (spray with soapy water or try to slip a credit card between the bladder and the side, gently, and if goes in fairly easily may be indication of bladder lead.

Also I understand there is another option but I need to look at some diagrams.  Do I recall hearing of some venturi part that if goes bad could cause this? 

Recall I posted....I had a leak at the valve AND at the plastic moisture collection/discharge bowl on the compressor.  It required both be fixed before the running of aux improved.  I still urge the pressure gauge be installed, been real help to me

Mike
2001 U320 4010 Build 5878 (Gus)
Wrangle Unlimited Toad
Nacogdoches

Re: Auxiliary Air pressure pump activation

Reply #16 –
Thx for the prompt reply Mike and Jackie:

I did soapy spray around the slide bladder in the past with no leak,  but will give it another shot and also try the credit card test.  As far as the pump, I soapy sprayed the discharge bowl and all over and no leak apparent.....if there was a leak I would imagine the pump would have continued running when valve shut off?
Not sure how to plumb a gauge at the aux pump; guidance?
Fiddler
1959 Parris Island grad
40' 2001 U320 Build 5875
1999 Suburban K1500 toad
1986 Corvette Pacecar
ssoftail@comcast.net
 

Re: Auxiliary Air pressure pump activation

Reply #17 –
Fiddler, I will post a few photos and hope they self explanatory, but if not send me a pm with phone numbers and I will try to describe to supplement the photos.

Note on the plastic bowl soap leak test however that I could not see the leak when I looked.  MOT and I thought we fixed things by changing out the bladder cutoff, a brass valve in a photo (first) here as the original was leaking and usually suspect.  But after we replaced the valve,  Mr Risch did still not like the behavior of the aux (it was taking 10 minutes to cut off and in past would in 3 minutes).  So with much crawling around in the bay, he found a major leak in the plastic bowl (second photo), a crack, that seemed better and worse at times.  In our coach you have to get into the bay and look back out toward the door to see the bowl.

There is another thread that describes this episode if you want to try the Forum search engine for it, but the two gauge photos may be enough?  Note, my gauge is connected to the bay lighting circuit so if you open the bay, the light goes on in the gauge. 

 I would be careful using the credit card, not force it, but is a common trick used at MOT.

Mike
Mike
2001 U320 4010 Build 5878 (Gus)
Wrangle Unlimited Toad
Nacogdoches