DON
Forum Replies Created
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I just installed those exact bag numbers on all three axles about a month ago. No problem raising the coach above ride height with level low. Our 98 had the original bags all the way around. Glad to get them changed!
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BTW, we have a member who recently had an experience with NCTS. I hope he will post his experience.
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JJerry,
Thank you so much for the directions! Linda
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crafty b, here is some air ride and leveling system info from “PrevostService” I keep in my logbook that you might find useful.
Burketts valves were what Prevost used in the mid to late 90s as a replacement for the Norgren three way valves. They come either NO or NC and they cannot be altered. The first versions of the valves did not have a return spring in them and we had numerous issues where the valve would stay in the midway position. This led to air systems not building air correctly. Normally the bad valve was on the tag lift system and by simply cycling the system you could get the valve to seat itself and the air would build correctly. Burkett came out with a valve with a return spring ( the new Burkett valve) but we went back to Norgren valves eventually. Another issue with the Burkett valves was they were made for a much cleaner, industrial application. The coach pneumatic system in not a completely clean and dry environment. The Burketts did not fair well on the coach. The Norgrens were more robust and did not mind a little oil and water in their working environment.
Most of the people in Prevost service do not know anything about the Norgren numbers. Prevost parts secures the correct Norgren number for the application from the engineering department and then a Prevost part number is generated. To get the Norgren number we would have to get someone in parts to look at the cross reference file for the correct Norgren number. That is why you may get a blank stare from a tech if you come out with a Norgren part number.
As noted also above the type of valve you need (NO or NC) will be dependent upon your pneumatic configuration in the rear of the coach. Up through 1996-1997 the plumbing of the tag axle lift circuit required that there be sufficient air pressure in the auxilary air tank air sytem to properly pilot the valves associated with the tag axle and tag lift system. Thus you needed good aux. air pressure to keep the coach at normal ride height in the rear of the vehicle. Lack of proper air through an air leak would eventually reduce pilot or control port air pressure to the point where the internal spring tension of the valve overcame the control pressure and the system cycled much the same as if you had flipped the tag lift lever. The difference being that there is no aux air pressure left to do anything with the system.
Engineering at Prevost redid the pneumatic “plumbing” of this circuit in 1997 so that there were no control pressures to any of these valves to keep the tag axle down and the tag lift circuits off. There was a maintenance bulletin released “Service Bulletin 96-14B) to increase the reliability of the pneumatic system. The bulletin can be found at https://secure5.volvo.com/technicalpublications/pdf/SB96-14B/pdf. There were various kits made at the time for different models. These would come with instructions and valves that had the proper brass fitting for the application. The kits also included an inversion valve that had to be plumbed into the circuit. Prevost has always cancelled the brake boosters on the tag axle when it was lifted to prevent tire damage. As we were changing the way the axle was controlled we had to change the control of the Bendix R12 valves that controlled whether there would be brake application pressure sent to the boosters on the tag axle or not.
The modification takes some time as the old valves need to be removed and air lines properly identified. Then the new valve installed correctly and the inversion valve installed. Plus the light circuit in the dash had to be changed to reflect the lack of air pressure in the controls when the vehicle was in the normal ride height position.
All that being said: to check your system! Run vehicle and get all air tanks filled. Turn off coach. Open accessory (auxilary) air tank and bleed down the pressure. If the coach has the newer system installed the vehicle should NOT settle in the rear as if you flipped the tag lift lever. If if does squat, then it most likely did not have this modification done.
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I’m still not clear if you have the tag logic or not, if so, then you likely have an aux air leak that you should be able to hear with the engine off. I assume the 6 minutes until it drops is because the logic dumps the tag as the aux air leaks down to a low number. If the bus is running, the compressor is keeping the aux supplied with air and it stays up.
None of the 45′ I had would lift the tag, the 40′ would. I know some 45′ will lift the tag, but it has to set for a really long time with engine running.
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On your coach they are behind the rubber fender liner in front of the drive axle. I always pulled the outer drive wheel.
Don’t get under your coach unless it is supported. Especially because you are working on the suspension. Raise it, support it, dump all air from the air bags just to verify it is supported.
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Don
Thx for posting that bulletin. I’ve been told that existed, even Prevo had a difficult time finding it and what they sent me was similar but for an H.
I have a 95 chassis XL40 with the old tag logic. It will dump tag when AUX drops to about 20 psi. My VIN is S1001572 which (is close) but according to bulletin doesn’t (or shouldn’t) apply to XL40 MTH shell, only XL45.
Has this been done on your Liberty? Or maybe it is newer tag-logic setup. If it was changed did you do it yourself and pretty straightforward?
Thx BG
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If you haven’t swapped coils I would think that would be easier, but if you have and no change then see if holding shop air on the air line out of the 3rd valve does allow the coach to go to ride height.
But if it does not and since you ruled out arm adjustment you are getting to the point where you need to start verifying the 5 port norgrens are shifting. Moisture, or sludge created by the presence of moisture in the norgrens will really mess up how a coach responds to level low commands.
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engine running I get a very small amount of air coming out of coil 3 supply line to a valve just left of the 5 coil bank and nothing when the motor is off so it appears to be working. When I attach the coil 3 line back to the valve the front will raise and nothing out back. I got a look at all three leveling valves and the arms are straight out not on a angle. The rear 2 are new front is not.
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Are the others 12 or 24.
Liberty is the only converter I know that uses 12V coils and then only on their Classic model. And not on the center coil which is the ride height control coil.
Just to make sure I understand when you have the key off and crack the nut on the compression fitting no air should come out, but with the engine running cracking the compression fitting has air coming out?
That is who it should be because that is shifting all 3 5 ort Norgren valves to the ride or road position.
If you have ruled out a bad solenoid valve on the manifold the next step is to verify the ride height valves are adjusted correctly. Manually set the coach at the ride height which is approximately 11 inches from bay doors to the ground. Then look to see each ride height valve arm is centered and level. If the arm is perpendicular to the valve body, not up or down I think you can rule that out. I believe you can see each, but be careful, do not get under the coach unless you have it supported at the chassis support points.
If the valves are adjusted OK then it starts getting more complex.
Please just verify it does nothing when you have the coach up or down and the go to the road or ride height. I say that because if it moves toward the ride height it could be a ride height valve arm adjustment, or if that is not it, the coil is good you might be dealing with a hydraulic lock due to moisture or sludge in the 5 port valves. That is the next step to check.
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i shut the motor off in drive mode and after maybe 2 minutes the rear air released and now its sitting at around 9” and it sounds like a goose quacking every few seconds right before it dumps the air. it is not on bottom there is still air in the bags. front is still up
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OK, here is what I think I know.
Your issue has nothing to do with the system logic that caused air in the tags to dump air if accessory pressure dropped lower than about 30 PSI.
What I am not clear on is it sounds like you can make it do whatever you want with manually controlling level low, up or down.
That tells me the spool valves are responding to level low commands. But when you tell me the road or driving position when selected makes the front go up and the rear go down it could be a number of issues. My concern is you are not answering my original questions which wlll start pointing me to possible answers.
It could be the 5 port valves are screwed up with moisture and the moisture will not allow the spool to shift properly. It could be someone was messing with the ride height valve adjustments. It could be someone has gotten creative with a “repair”. Since you haven’t said the converter I still do not know if you have a motorhome shell, and entertainer shell or a seated coach shell that was converted. If it was a motorhome from the start was it a pure Prevost level low or was it modified by the converter?
Please help us help you.
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There are two “timing” sensors on the S60. Synchronous reference sensor (SRS) and timing reference sensor (TRS). Yours looks like the TRS. See picture
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Dorel,
Faye is your girl you need to take pictures of your drive end and send to her. The mechanics when they replace older shades sometimes keep the parts that is how I got mine from Faye two years ago. She is the sharpest person in the parts area in Colburg, Or. The blue pasley fabric strip on mine is held on with heavy velcro. When you pull one end loose you’ll start seeing the screws holding the valance. The valance was just bare plywood under deco fabric strip on mine with ultrasuede treatment on ends.
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I will say it here, and anyone can read into what I am saying whatever they want.
Some “expert” inspectors are buttering their bread on both sides. The do inspections for dealers and brokers, and re-inspect the coach for a buyer, not revealing a business relationship with the dealer.
A second comment is regarding the conversion. Each conversion is different and I would be useless inspecting anything but a Liberty because my ownership history is with Liberty. These coaches are too complex to expect someone who does not have years of work experience or ownership experience on the conversion being inspected to do a good job.
I said enough.