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Level/ Low
I have a question about the level/ Low system? The knob controls the 5 stack and I know each of the 5 valves open a air valve to raise and lower coach. Top valve is air supply! what is is function and when is the top valve 12v solenoid active/ 2nd valve down is for fronts/ 3nd one down ride height 24v/ 4th down is right rear/ 5th bottom is Left rear. So when it’s on left rear you drop works fine when you inflate (raise) left you push up it raises up but when you let up on switch you can hear the rush of air release and it will go back where you started, to raise it up you have to go beyond what you want and hope it settles where you want it, is it a bad valve bottom valve?? Looking at Virtual PDF could it be the Norgren valve left bulkhead K910058?
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14 Replies
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I think I understood what you are saying, but let me state it as I understand it. There were multiple questions so see if I got it right.
You seem to question the 5 solenoid stack and each valve’s function. As you described the functions appear correct. You indicate if you put the rotary selector in the left rear position and you move the rocker switch to raise the left rear I think you are saying that on your coach, as soon as you release the rocker switch, air is exhausted and the left rear drops.
That is not right. Does that occur when you select right rear or front on the rotary dial? I do not have or ever had an unmodified Prevost Level Low system on a coach, but I have worked on them and if my memory is correct, except when the rotary knob has the road or driving position selected the rocker switch adds air to the appropriate position when “up” is selected, When the rocker switch is in the neutral or “off” position air is locked in the air bags, and when it is in the “down” position air is exhausted from the selected air bag.
The only time I worked on a level low system and it wasn’t functioning as I expected I traced the current from the dash switches to the associated solenoid valves to rule out a switch defect, then verified the appropriate solenoid valve was functioning by cracking the air fitting and hearing air escape, and then I followed the air to the Norgren valve that was to receive the pneumatic signal. When air was at the correct Norgren valve I removed and disassembled the Norgren valve and found it to have a hydraulic lock as a result of moisture and associated aluminum corrosion slime making the valve spool unable to shift to the correct position.
The process of chasing the Level Low System functions is a pain, but for me to follow the electric and air the methodical approach as described leads me to isolate the problem.
When you stop commanding the left rear to rise, you should be shutting off the air supply valve so air from the accessory tank is not entering the air bags, and it should not exhaust air because the exhaust valve in the steer compartment should be closed. (I think. I am going from memory without pulling the schematics.) Keep in mind Prevost has made evolutionary changes to the Level low System over the years and converters have made modifications to the Prevost system so it is hard to make accurate generalized statements which is why chasing air and electric in a systematic manner might be the best way to determine what’s what.
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It’s only the left side does it, it’s like when you push raise on left side it raises but slow to shut off valve and it drop back down,If you hold it for a bit it raises,and over raise it, and it will drop a little and then going down no problem a little at a time. When the switch is on left and you push raise the bottom air valve on 5 stack pushes control air to rear left sidebulkhead Norgrenvalve K910058 on control port changes air direction to fill left rear bags, but its like valve drags to shut off, and air rushes out. Both front and right when releasing raise a short burst of exhaust then stops
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I emailed you the “suspension virtual pdf”
Make sure the leveling switch(es) is functioning properly. Use a multimeter down at the five stack and or just above it at the buss bar where all the various colored wires attach.
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Under each 5 stack coil is a “armature”, pt# 54462-31, $36 ea from IMI Norgren. Something else that can get buggered up by moisture, like the Norgren spool valve you mentioned.
Mike Harper
2004 Marathon XLII -
Like I said in my first post and as Don reiterated, verify the switches are working by checking for current at the solenoid valve coils, but based on your post above my guess is the Norgrens (one or more) aren’t functioning right. What is their age, and more importantly do you know if the system has ever had moisture in it.
More than a few times unexplained level low operation has been traced to internal valve corrosion dragging the spool and delaying its operation, or a hydraulic lock preventing any spool movement.
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I’ve replaced most all the Norgren valves but not the 5 stack valves, but I do have them, so I think I will try to replace the lower one
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I’m not convinced they are the issue and you can quickly check their operation by cracking a fitting to see if air flows when it is commanded by the switches for the level low.
And to be more precise, make sure no air is flowing when it isn’t supposed to as a result of a leaky solenoid valve.
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Good idea Jon thanks’
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If the fittings are push in I just added to your workload because they need to be replaced with compression. My 97 had compression fittings, but my current one has push in so my change over to compression is in my future.
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Sometimes my brain falls asleep and I forget to think of other ways to sort out problems the easy way.
If your left side rear is the only function acting goofy switch the air lines at the solenoid valve manifold. See if the problem goes to the other side. If it stays on the LH side (when using the RH side at the switch) the problem relates to valves.
That seems way easier than chasing problems at the valves, which in this case means removing the front drive axle fender liner to get at the 5 port Norgren. You may still have to do that, but at least you will know where it is.
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Jon! I replaced all 5 Norgren solenoid valves and it has all compression fittings, I write everything down when I do anything on the Bus , I’ve replaced 3 Norgren valves up front, 2 above tag on driver side 1 over tag on passenger side, and I wrote down that I replaced 2 on rear bulk head, and now 5 stack valves, But! I saved all the old Norgren valves and wrote on box what,and where they went, all old valves are accounted for except the driver side Norgren on rear bulkhead, I must have made a mistake on writing it down, So! that missing valve controls left rear. It seems better after replacing 5 stack valves so I will try it for a while before I replace the last Norgren K910058 Prevost wants $179 the same valve from Norgren K81EA00KACKAC is $104. I found I had a new valve in my stock, that was probably the one I missed. I posted a while ago that I installed a new AD9 dryer and the air is clean and dry now. I’ve learned how important the air dryer is, the 1st owner let the dryer go and the little aux compressor ran a lot which causes moister, air system was a mess, I never have to run aux compressor anymore,but if I do I added a water separator filter,and I will pay attention to the dryer, cause I know what a crappy dryer will do.
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Art,
I think the 5 port valve may be the answer but rather than speculate you are going to know for sure.
The problem with moisture is not always getting a volume of water in the system, but in creating a humid system because springs rust, the raw aluminum bores in the spool valves get white corrosion eventually forming a gray sludge, the inside of brass fittings gets a green discoloration, and things just don’t work as well as intended.
The problem with moisture is it is damaging in a slow subtle way. There is no magic moment when something is working perfectly, and then it isn’t.
The 5 port valve in the rear does 3 things. In the neutral position it shuts off all air flow and whatever air is in the air bags is locked in. In the driving or road height position the spool shifts and air flow into or exhausted from the air bags is controlled via the ride height valve. In the manual position it shuts off the ride height valve and allows you to open the air supply to add air to the air bags or open the exhaust valve to deplete air.
While I still suspect this is a valve problem I cannot figure out (yet) why air is exhausted when you take your finger from the switch, especially because you have new valves. Even if the 5 port is lazy and is not moving the spool as it is supposed to there might also be something else at play here.
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Jon I think the air that exhaust is the air thats in the air lines between the valves,When you raise, The 5 port on the bulkhead opens to add air, the Norgren in the steer opens to air supply, When you remove your finger from switch the rear 5 port closes valve, the Norgren in steer shifts from air supply to exhaust and compressed air in the air line from rear to front exhaust. the front is a short burst because it’s right there and both rears are longer because or the length on tubing.
Jon! Thank’ again for all the time and knowledge you put it to all these questions, I just looked up how to read date codes on my tires, steer 2016-drives 2017- Tags 2015 , A good thing to keep track of.
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Just let us know what you find. Especially if my theory is wrong because one thing Tom and I want to control on PC is to insure nobody is mislead by lousy information.
As we all gain and then share knowledge it makes owning these complex vehicles much more enjoyable.
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