Hi,
On our first road trip. Rear tank air pressure reaches 150psi. Front tank at 110psi. Is the high rear tank pressure a critical issue? Compressor governor issue? Something else?
MOST IMPORTANTLY: Can we drive safely for a few days? 160 miles total until we have appointment at Oregon Motor Coach in Eugene on June 7th and 8th.
Thanks!!!!!!!
My first guess would be a bad gauge. Both front and rear tanks are filled by your wet tank. So for your rear tank to be at 150psi the wet tank would also have to be at 150psi. Since the wet tank feeds both tanks if the wet tank is 150psi both tanks should be at 150psi.
If you can switch the connections on the back of the gauge to see if the high pressure follows.
see ya
ken
I agree with Ken. First suspect is the transducer. You should have a blue box (maybe gray) in the dash spaces. Two of thr plugs are for the pressure gauges, easy to swap them there.
When the electronic gauges go and a new transducer doesn't fix it the easy and for many a better solution is to go to direct read mechanical gauges. They don't go to zero when you shut the ignition off
Yours may have air lines up into the dash are for this. Look for Drawing B2254. Rhe one I attached is the right build number range but is for a U320 with a tag. Probably close.
You should be OK. The tanks should be the same pressure.
Thank you!
Peace of mind is worth more than I can tell you!!. Will tell OMC shop of issue and see if air pressure gauges will be available to install when we visit on the 7th. I prefer the direct reading air pressure gauges over the digital ones FT installed.
Peace of mind is knowing what is actually going on in your air system. If you have the coach in a shop where they are working on the air system, you might discuss the possibility of adding a
wet tank mechanical air pressure gauge in the engine compartment. It is a fairly simple job, and the parts are inexpensive.
The D2 governor, which is located somewhere in your engine compartment, has a unused bottom port which constantly "sees" wet tank (reservoir) air pressure. You only need to run a air line from this port to a pressure gauge located in a place easily observed from the engine compartment hatch. Each coach will be laid out differently, but the basic concept is simple to implement.
Knowing your wet tank pressure can be helpful in diagnosing many air system problems. The wet tank is the
first storage tank in the system. At the moment the air compressor unloads (air dryer purges) the entire air system should be at the same pressure, which will be indicated on the wet tank gauge. Comparing the wet tank pressure reading to the dash air pressure gauges can help pinpoint problems in the air system. Also makes it easy to verify and/or adjust your cut-out pressure on the D2 governor.
See the links below for a helpful diagram of the D2, and link to an old post showing my simple wet tank gauge installation.
Dash Air gauge has two indicators. one white, one red.. ??? (http://www.foreforums.com/index.php?topic=24878.msg195836#msg195836)
Haldex D2 Governor Service Data (http://beamalarm.com/Documents/haldex_d2_governor_service_data.html)
Chuck,
I like your idea for the air system. I've been looking for ways to monitor/verify/diagnose the coach systems. Having the Vmspc has been great for the engine/transmission, but cannot monitor the air system.
Anything I can do to make sure the wheels keep on rolling safely is a big help in enjoying the ride.
BTW: Any easy way to have a low pressure warning on the front/rear tanks when the gauges are mechanical? (I'm assuming that without the "transducer" blue or gray box there will be no low psi warning)
You already have a low pressure warning - it is part of the HWH leveling system. On your rear 6-pack manifold there is a pressure transducer. It's purpose is to monitor
system air pressure, and to activate a warning light and/or a audible alarm when pressure drops below the switch set point. The set point is usually around 80 psi. You might find the specific setting in your HWH Leveling System owner's manual.
When you first turn on the ignition key, all of the warning lights/icons on your dash should light up. There should be one that says something like "Leveling System" or "Air Pressure" or "Low Air Pressure". I haven't seen the dash on your model coach, so don't know specifics.
HMMmmm.... Your question got me looking through the archives. I may not be totally correct about how the low air pressure condition would be "announced" by your 2002 model coach, in the absence of the "blue box". Some of the other owners with newer model coaches might want to comment. Like perhaps Roger? See threads linked below:
Air Brake Low Pressure Warning (http://www.foreforums.com/index.php?topic=30412.msg263314#msg263314)
Mechanical Air Pressure Gauges (http://www.foreforums.com/index.php?topic=30213.msg260315#msg260315)
Mike J, I went to mechanical gauges and do not get the alarm warning if low air pressure. I had to disconnect the alarm when went to mechanical because otherwise it thought all the time I had no air pressure.
Michael (& Jackie),
Do you have a "Level System" light or "Level" light on your dashboard? Does it stay on until your air pressure gets up to about 70 psi, and then goes off? If so, that would be the light controlled by the HWH rear 6-pack pressure switch. If it illuminates when you are driving down the road then that could serve as a visual low air pressure warning light.
On my coach if the Green Travel Light is on, I'm good to go. If the light is out, then something is wrong and the coach may not be in ride height.
Right, John - that is the green "Travel" light on the HWH control panel. It is controlled by the pressure switch on the rear 6-pack. But there should
also be another "Level" light (controlled by the rear 6-pack pressure switch) on the
dashboard, . I'm just trying to determine if the newer coaches have that dashboard light.
Chuck, as other wrote, I have that green travel light on the HWH control panel by the driver left arm. Not good to go unless it lights, will lock me out. In my manual though it says to not trust that completely, that should go out and look at the coach to be sure it at ride height before heading down the road......I should but gotten into bad habit I guess of trusting the light.
That light is active when I am getting ready to go, for example if total air pressure too low. Or leaving and take coach out of level, it will come on and signal it ok to drive.
On the dash though I do have a light that comes on.....why do I not know when it does not or what means.....I cannot say it lights up if I lose enough air pressure while driving. At least it has not yet done that, thankfully. But it does note the level system is active, not sure if that is same as failing air system. A good thought about that message, Chuck. And it is not simply a green light but a couple of words. Just like similar for the park brake system being on.
Will see if I can find out more later today, maybe. Just in time crunch today.
Correct Chuck, I have a light on my dash that says low pressure, plus the alarm keeps sounding as long as the pressure is low.
Thanks, John.
So, if the OP's 2002 coach is the same, it should have two lights on the instrument panel that pertain to system air pressure. One is the "Level System" light that is controlled by the rear HWH 6-pack pressure switch. The other is the "Air Press" light that probably gets its signal from the "blue box" that powers the electronic air pressure gauges. If mechanical air pressure gauges are installed, and the "blue box" is disabled, then the "Air Press" light may no longer function (like in Mike H's coach). However, the instrument panel "Level System" light should still function, and it can serve, along with the annunciator (beeper), as a warning of low air system pressure.
Hey John, Chuck,
Not sure where you guys are getting your information from or if there are really differences year to year.
See attached picture of caution label that is on my left dash.
It states exactly the same caution in my owner's manual for this coach (2002) and for our previous (1998). My green travel light on the HWH Panel comes on at some much lower pressure than 80 psig, as in somewhere between 20 and 30 psig. I always understood that that sensor was on one or more of the HWH six packs, and simply means that the air bags are receiving air and it has built to some LOW pressure.
The caution to not move the coach is not as important on 2002's and after, because the frame is 2 or 3 inches taller and the wheels do not contact the overhead panels when the bags are low in pressure or completely aired down. With 2001 and prior coaches, if you move the coach when the green light comes on, you risk scuffing or destroying the panels overhead of (particularly) your rear axle(s).
There are several threads reminding Foreforum members of this. Haven't searched but should be easy to find.
Edit: Here you go:
Travel Mode (http://www.foreforums.com/index.php?topic=28098.msg232404#msg232404)
As far as the two "warning indications on the dash" go, I have only one air pressure associated warning light ("Level System") on the 2002 and had only one on the 1998. The Yellow "Level System" warning on the dash is simply a repeat of the green ""Travel" LED on the HWH Panel. If the ignition is on and the HWH senses less than 20-30 psig on the one (or maybe more) HWH six packs, the light and the alarm on the dash continue.
The DOT low air system warning (unadjustable pressure switch that acts at 62 psig decreasing) comes off of one (or more, maybe) of the pressure switches under the dash. There is no specific warning light on the 2002 dash, and I can't remember on the 1998, but the same warning "Bell/Beeper/Chime" under the dash is used to announce the low air pressure condition. It continues until air pressure under the dash reaches something greater than 62 psig.
HTH,
Neal
Neal,
Your green travel light on the HWH panel may be suffering from "Premature Illumination"...a common condition in the elderly. ;)
The page from the HWH Text Book that I linked above (Reply #6) states that "Pressure switches used to monitor system air pressure are usually set at 85 psi, although some manifolds have a pressure switch set at 100 psi." If that is the case, it should take close to 85 psi in the air system before the green HWH panel travel light comes on. On our coach, the green light comes on at about 70-75 psi, which I feel is close enough for government work.
The warning sticker in your photo repeats the same warning found in my HWH owner's manual. That is, seeing the green travel light illuminated DOES NOT mean the coach is at proper travel height and ready to move.
Neal, my green light comes on at about 90psi and the alarm goes off. I don't move my coach until I am fully aired up to 120psi. I never move the coach as soon as the Travel Light comes on.
John M
Guys,
John, sorry. When you said "On my coach if the Green Travel Light is on, I'm good to go.", I was concerned that newbies would take that as a license to move a coach, which is not what the HWH "Travel" green LED is meant for.
Isn't/aren't the Green Light Pressure Switche(s) on the supply side of the HWH six pack manifolds? If the switches are on the bag side of the six pack manifolds, I didn't know that the bags always ran at greater than 85 to100 psig.
The point being, pressure on the inlet side of the manifolds tells us nothing about bag pressures and travel attitude around the four corners of the coach.
Neal
Neal makes a good point. Have seen many coaches with "skid marks" in the top of their wheel wells.
I have done it myself, let air leak down then started coach and soon as alarm stops, try to move coach.
As said, think around the 2002 and up have different size stops, so coach will not drop far enough to allow wheels to contact top of wheel well. Think weight of coach and design of your HCV, as well as air pressure, will dictate how quick your coach will reach proper travel height.
Would putting the taller stops "fix" my 2000, or were there other changes, too?
Thanks,
Trent
Being used to having a Newell I'm in no hurry for it to air up. Which is pretty quick on a FT.
Trent,
Putting taller suspension stops on the frame rails only helps to keep the tires from crushing and/or deforming the overhead panel sheeting and flooring, especially when one is trying to auto-level with very uneven site conditions. I tried for years to get an answer out of FT on what height buttons I could add to the frame rails on the 1998 U270. I never got an answer.
The problem is that when the buttons are too tall and the coach is lightly loaded (i.e. - the air bags are going to be on the soft side, going down the highway), then you may well bottom out the suspension when you encounter severe surface conditions. It happened to us many times when running an essentially "Zero-Loaded", 1998, 36', U270 on frost damaged roads in New England.
The reason the 2002's and up don't have the tire/overhead scuffing problem is that as slides were added, the underlying frames had to be made taller and beefier to make up for the added weights and the weakened sidewalls, as well as the increased susceptibility to twist and stress crack at the corners of openings. So in 2002, you will notice that the distance from the entry step to the second step into the coach is a full three (+) inches higher than in 2001 and earlier. That's all in increased frame rail depth and the frame rails are stronger material as well. The beefed up frames also mean less susceptibility to sidewall anomalies associated with bulkhead weaknesses, partially countering the mythical favoritism shown to 2001's as THE premium year coach. Without the end cap issues forfeiting the MANY gains made over a 2001, I would much rather have a 2002, 3, or 4, due to the frame improvements, especially if it's a non-slide in those years. But that's why we have the coach that we do. However, this is all just personal preference. We all know that they are all good up through 2005 or so --- which is another whole world of discussion and personal preferences.
Simple answer to your question: NO, frame buttons are not likely to help you much in "Quick Getaway Situations". Also, they are somewhat "iffy" to use, especially on a lightly loaded coach.
HTH,
Neal
Tulsa (regarding installing higher frame stops)
The other factor not mentioned here, yet, is that increasing the height of the metal frame stops with metal would increase the risk of metal to metal contact when the suspension bottoms out - this is very undesirable because it will cause permanent damage to the suspension components. If a bottom out incident occurs, there will be little damage if it happens with rubber components (i.e. the rubber stopper inside each airbag) which is designed to stop over compression of the air bag. I installed half inch spacers on top of each air bag so that, when on level ground with coached lowered as low as it will go, there is a very small gap between the top of the tire and the floor. If not on level ground, some tires will still touch the floor when coach is lowered. I also raised the ride height by 3/8 inch. I wanted to raise it a half inch, but adjustment bolts were not long enough.
If you decide to increase the height of the metal frame stops, be sure to use rubber rather then metal.
Gentlemen,
All the green travel lite tells us is that the 85psi switch on the rear HWH manifold has sensed 85 or more psi in the air system.
That switch only has two functions, less that 85psi and it turns the low air pressure warning system on. More than 85psi and if the key is on and the level system is off then the HWH computer will send 12 volts to all the travel solenoids (and the green travel lite comes on ) to hold them open so the ride height control valves can set the coach at the travel height.
Just because the green travel lite is on does not mean all travel solenoids have opened. The only way to confirm travel height is to take that last walk around and look at the height of each corner.
At this point since the engine is running you have a chance to see if anything is running out of the bottom.
Does this mean that one would be able to drive a 02 or later if a air bag should go out?
Chappell, I think blowing an airbag would cause an air loss greater than the engine compressor could keep up with. Pressure would get below the low limit, you would get a level system warning light on the dash and at some minimum pressure your parking brake will come on. It cannot be released until there is sufficient pressure. If you are not in gear the low level system warning prevents you from engaging the transmission. If you were moving and the low level system warning came on I don't know what the transmission will do.
In addition to Roger's comments (above), even if you could plug the hose to the blown air bag and restore system pressure, I think trying to drive the coach that way would be inadvisable. Having only one air bag inflated on a corner of the coach would put a lot of strain on the suspension components, as the other bag tries to maintain ride height. I would be afraid of causing some very expensive damage to hard to replace parts.
Not a real expert on this, but I think you could move the coach at a slow speed, not really drive it. Had a right rear ride height valve go out once when driving and didn't notice it until I smelled rubber. No real damage, although the thin plastic above the wheel wore through. The frame stops carry the weight of the vehicle when the bags are deflated not the top of the tires, even on the older coaches.
Thanks, at least you could get off the road with very little damage. Maybe.
Chappell,
I'm new to this but can share our experience with a completely blown rear air bag behind rear axle. Had to move coach, but I wouldn't call this "driving" the coach. Site was out of level and had no space alongside busted bag to work. Moved 30 feet to a level open space. At a crawl. Travel light never went out. Warning chime never stopped. Brakes worked. Coach was listing and down in the rear. We dumped all air. I'm thankful there was no further damage. The additional frame strength commented on by Neal is probably why. Plus our 36' length, no slides. (At least I'm hoping this is so. I haven't seen anything tweaked or cracked. Coach goes into shop tomorrow for some inspections and minor repairs. I'll be looking everything over along with a tech.)
Someone said the travel light insufficient to determine fully inflated suspension. We never move until front/rear air is at least110psi. Travel light is green and warning chime stops before 110psi. Hard to say accurately at what psi travel light goes green. Our gauges are acting weird. (See last comment below). We do final walk around and visually check for coach sitting square/level etc.
I started this thread over the erratic reading of our rear tank vs front. Today arriving at OMC in Eugene the rear gauge was all over the place. Hope to repeat it tomorrow. Easier to find culprit.
Update on rear tank vs front tank air pressure difference, We swapped the electrical connections between the two gauges and the high psi rating swapped as well. Gauges seem okay. At this time, believe problem to be the sensor on rear tank. Schematic doesn't indicate an electrical transducer etc. box under the dash to translate tank pressure to electrical for the dash gauge. See FT drawing of air tank piping. Red dots by the gauges, Blue at the tank sensors.
However, there is an alarm and power box for gauges, (probably under the dash, haven't put eyes on it yet). It is on the 12v wiring diagram. Red dots at gauges, Blue at the alarm/power box.
Current plan is to replace the sensor at tank first. Since the alarm box also supplies power to the gauges. Could be fault is there. ???
Much appreciate everyone's input/answers to my post! Hope the photos are clear, taken with a phone.
Chappell,
The green travel lite and 120# of pressure do not insure that you are at travel height.
The travel lite is not a solenoid position indicator, the lite is only an indication that the HWH computer is sending 12 volts to all the travel solenoids. If one solenoid valve doesn't open that corner will remain at the height it was at when the system went into the travel mode.
I learned this one the hard ($) way. Drove home from a campground and found a windshield cracked top to bottom in the curved corner. The left front travel solenoid has failed to open. I had full air pressure and a green travel lite.
You have to walk around and check each corner to insure that you are at travel height.
You can do the Foretravel Shuffle to be sure all the compartment doors are latched and look for leaks on that walk.
I never found a travel height problem again but I felt good as I drove away.
So previous plan to replace sensor on front/rear has been changed. We already know that the gauges are good. Realize now that the wiring on sensors at tanks should be switched to determine if problem is a sensor or not. After that the problem would be in the alarm and power box under dash that feeds into all the dash gauges. As posted elsewhere on forum there is no replacement for this d...n box whether it is blue or gray!
May have to go to mechanical gauges for air tanks. That is okay, even preferable, IMO. Many of you have done this modification either out of necessity or choice. But, in the future, will I potentially have to replace other dash gauges too as this box degrades? James at FT seemed to think so. Wife isn't too happy about there being no alarms for low air pressure. It doesn't help my discussion with her that we have the Vmspc with alarms programed for everything else except the tank pressures, which are unavailable in the Vmspc.
Possible solution?: Has anyone with mechanical air tank gauges ever installed a tee in each of the gauge airlines so an adjustable 12v air pressure switch can activate an alarm should tank psi drop below a set point? The working air pressure rating on the switch would have to more than cover the normal range of zero to travel mode up to 110-120psi. Wouldn't want a failure in the switch at full coach pressure.
Thanks!
I see no problem in locating and installing a separate low PSI swithh and wiring it to an in-dash alarm.
Probably look for one in the 80 PSI range (well below normal operating PSI, but well above parking brake set).
I have looked at adding an a/d box to get both analog (air pressure) and digital (turn signal on/off for example) and adding a single line display above VMSpc to display more information. Lots more work than it would be worth. I have suggested to Silverleaf that some additional inputs would be nice. Someday perhaps.
You can add a low pressure alarm. If you remove the analog gauges from the gray/blue box and its alarm function is still working the annunciator will start beeping and will not stop. Cut the wires to it or add a switch to shut it off. But then you lose the turn signal beeps. You can work around that with a couple diodes and some connections to the turn signal wiring.
A quick Google search turned up this product page. Looks like they have several different versions of pressure gauges with built-in switches. The gauge pointer acts as one contact, and when it touches the adjustable low limit contact it completes a circuit. Looks like it could activate either a warning light, or a audible alarm, or both. There are probably other similar products on the market...just need to look around.
20P / 25P Series | FW Murphy Production Controls (http://www.fwmurphy.com/products/gages/20p-25p-series)
Thanks Chuck!
I like this approach. Much appreciated, switch and gauge in one package. I'll do some web searching to see what else may be available.
Best, Mike
Hi Roger,
On our coach the turn signal chime has a rheostat to adjust the volume. It also chimes until travel mode is reached. I assume this "ding thing" receives signal from the "blue/gray" alarm/power box? I couldn't locate ding thingie on wiring diagram. I have very limited wiring experience. My apologies for being dense on this. I do better comprehending mechanical modifications.
The most complicated thing I've re-wired so far was a busted weatherstrip sensor on my wheelchair van. Embedded in the rubber was a sensor on the sliding automatic door leading edge. A safety feature to stop door from closing if body parts were in the way. Toyota quoted, $350.00 to replace! Mechanic clued me into where to look on the web for a cheaper work around the problem. Instructions/pictures showed where to put a specific ohm resister into the lead coming from the weather striping. It matched what the "computer" wanted to see. Cost, 6 cents. Door works great again. All I had to do was solder the resistor in and shrink wrap it.
Your fix for the turn signal beep sounds a bit more complicated. Since I'm not able to get under the coach dash somebody else will be doing this for us. I'll need to pre-assemble everything and be able to tell shop guy what to do with it and where. Would greatly appreciate diagrams and how to with pictures if at all possible.
Update on air gauge replacement: Mechanical gauges are in. We kept the existing electrical gauges for now by installing a tee at each tank. Replaced the OEM tank sensors. Found the OEM electrical gauges read 5-8 psi higher than mechanical ones. Found 12 air leaks and replaced front regulator, tank drain valves, check valves, all front 6pack o-rings and and 2 rear 6pack o-rings. plus some air fittings. At least one brass fitting was cracked. Further testing found two more leaks that we ran out of time on, (another rear o-ring and the flare fitting at wet tank on air line from engine compressor). No leaks we found were very large. Coach has always leveled properly and achieved proper travel height. However, it would settle in front after 24 hours.
The following is all based on mechanical gauge readings. At idle the front is 110-113psi. and rear 115-120psi. However, going back to my original post, there continues to be a substantial? difference between front/rear tanks at times. Confusing to me since the two tanks receive air from the same source. Example: while driving, level road constant speed 60 mph, no braking, the rear gradually declines to 105psi then jumps within 5-10 seconds to 130psi. Once saw it jump back and forth between 130 and 115 several times. The front tank stays constant, slow movements between 102 to 115psi.
Possibly related observation?: Recently the air released during slight braking at very low speeds has begun sounding like a pig squealing. It used to give a pssst sound from coach rear. I've heard semi truck air brakes sound like pigs at rest stops. (please, no disrespect intended). But this is a new sound on our coach. Brake pads are excellent. Sound is air related?
I don't know what to think of the front tank staying pretty constant while the rear tank fluctuates between 105 and 130. And there is that squealing air sound under low speed braking.
Mike
This fluctuation could indicate that the rear tank check valve is bad causing the tank to fluctuate with the wet tank.
Have you had the dryer serviced? This could be the oinking you hear as it is purging air out the bottom.
You may have a governor (this is the thing that tells the compressor to start working/ pumping air) going bad and it can cause a strange sound.
Mike
Mike,
I think it is normal to some extent to see the air tanks loose and build pressure as you drive because the leveling valves in the travel mode are constantly dumping and adding air to keep the coach at travel height going over bumps down the road. Mine does it as well. Could also indicate that the leveling valves may have a leak if it is too rapid. I assume worn shocks could cause more suspension travel and cause higher air pressure fluctuations. That's my take on it.
Mark
The needles on my coach generally move together up and down, but once in a while one of them gets a bit ahead of the other one.
I think I still have a leak somewhere, as the white needle is where it was when I shut down this afternoon. The red needle is down quite a bit.
Mike J, your tank pressures and ranges and variations seem OK to me. The two tanks are rarely going to be the same. There is only one line from the wet tank that fills both brake service tanks, the front tank is first in line and then the rear tank. They both have different loads on them too. The rear tank feeds the retarder accumulator and two ride height valves. The front tank feed the fold down step and sliding step cover and only one ride height valve.
We all have leaks. It is hard to spend a lot of time on something that is not terribly critical. What is squealing? Next time out when you are first moving turn the retarder off and do a few firm stops. This will deglaze the rotors and pads. This may be what you are hearing at slow speeds with light brake application.
+/- 3% on a 150 psig guage is pretty good qaulity. Some may go as high as 5% or more. On pumps we only install one guage teed into the suction and discharge side with ball valves on each side to get an accurate differential pressure readings. Not wise on a coach.
Yes, dryer was serviced but shop doing work did not replace the check valve at bottom. We don't go to that shop anymore. They never did the complete air system check, (soapy water) I requested after replacing airbags. Shop we use now, Oregon Motorcoach in Eugene recommended replacing check valve on our next visit, (two weeks). They prefer replacing the valve whenever dryer is serviced. I'll also check into the air compressor governor. Thanks!
Thanks Roger, I understand the tank plumbing better now. Thinking more about the sound. I'm pretty sure it isn't the pads, but will check further. I should have described the sound as a Canadian goose being throttled. Pigs squealing is not very accurate and would be better applied to glazed pads. (I didn't know this thread would devolve into discussion of animal sound)
Thanks all! (BTW: I'm not obsessed with air leaks, Coach was on a lift I could get under with my wheelchair so it was easy for us to check)