[Archived]

HI. mine has done the same thing a couple times. and i have found the electrical plug off the manifold had uncoupled or had a bad connection. may have been due to me in that area working on something. just a thought.

[Archived]

Check the center solenoid valve coil in the 5 valve manifold that is in the steer compartment.

[Dick]

Thank you for the suggestion, what is th best way to go about doing that? Still trying to figure out this suspension stuff

[Bill]

I figured out how to swap the coil out with a different one, both 24 volt, and it didn’t make an difference, nothing goes up when idling but the hwh can raise it up, or maybe I just have a bunch of bad coils and just need to replace them all,

[David]

HWH can raise it up or the Prevost Level Low system, which is the rotational knob (left, right, front) and the up / down toggle switch, can raise it up.

[Jeff]

It is improbable all coils are bad or need replacement.

If you have the system set for the driving or road position the center solenoid valve opens and sends air to the Norgren valves that will introduce air to the suspension system via the ride height valves.

Verify air is flowing from that solenoid valve by cracking the fitting in the center position on the manifold.

That air flow will shift the five port Norgren spool valves.

It becomes difficult to understand how all the 3 Norgren spool valves would fail to open if air is flowing from the manifold unless there is a greater issue such as water in the system. When the accessory system is not dry all logic that is used to diagnose problems goes out the window.

I do not know if the HWH can be turned off and taken out of the picture so system analysis can be done.

[Archived]

Thanks, still trying to learn about this thing, so where exactly do I need to check and drain water from the system?

[Deleted User]

check or run temporary grounds.They seem to corode over time and you can’t see it.

[Brett]

A coach pneumatic system that has not been maintained has the potential to collect water. Once the system starts to collect water almost all logic associated with diagnosing and fixing problems gets complex and expensive.

There are two sources for water in the pneumatic systems. The primary is the engine driven compressor and any moisture laden compressed air is dried at the dryer. But the dryer requires a change of cartridge element periodically. I change mine at 2 years and as a result I have never had moisture from the engine driven compressor in the wet tank or the two brake system tanks.

Depending on the conversion, the second source for water in the system is the coach auxiliary compressor. Unlike the chassis system which uses a high quality high capacity dryer most if not all conversions use a poor quality means of trapping or containing water. As a result there is a potential for the aux compressor to deliver water into not only the conversion pneumatic system such as pocket doors, floor slide, etc., but also the chassis accessory system which includes the suspension system and its controls.

So how can an owner check for water? The first step is to insure the system is well maintained by using good dryer cartridges and change them as often as necessary. On the aux compressor side of the system, ensure whatever devices are installed are drained often and insure they are working.

To verify the system maintenance is working, drain all the air tanks periodically and do it in a sequence that also will verify the systems check and protection valves are working by starting with the wet tank, then primary brake tank, then secondary brake tank, then the accessory tank. If the converter has added a tank, drain that also. They have to be bled of all air pressure before moving to the next tank.

This procedure needs to be done beneath the coach. So any time the coach is in the air or over a pit, make sure the procedure is done. I check my tanks as described every 5000 miles or any time I am beneath the coach.

If you hire someone to do a coach service, make sure they follow the procedure.

Now if there is a suspicion the system has or has had water in it trouble shooting is going to require verification the 5 port manifold is functioning as required, based on electrical signals either from the Level Low controls or the over riding HWH. Once the electrical signal is verified to the solenoid valve coils, then check and verify air is passing through the valves to the various Norgren spool valves on the coach.

For example, if the coach needs to be raised to the driving or road height, verify air is passing through the center solenoid valve. That air will go to one of the small ports on the 5 port Norgrens. Verify air is getting to the port on the Norgren valve and if it is, air should pass through the 5 port Norgren to the ride height control valve which will pressurize the air bags.

All of this is shown in the Prevost Car maintenance manual available on line and is not only described in the section relating for the suspension, it is also shown on the pneumatic diagram for the coach.

Air can be at the control port on the Norgren spool valves but if the system has water in it, the valve can be hydraulically locked by water, or it can be locked due to an accumulation of corrosion caused by water in the system. The point is if the system should work, but doesn’t because the control manifold is functioning as required, the individual Norgren spool valves may not be able to work as needed. So a painstaking analysis following the air flow and verifying things are working is required until the failure point is identified.

I diagnosed a system problem when it was exposed to water and by checking for air flow at every point along the way it was determined the problem was a 5 port Norgren with so much sludge from corrosion it could not shift the internal spool to open the needed air flow circuit. The point being if any part of the system is found to fail due to moisture, it is probable the entire system has moisture issues and all working components need to be replaced.

[Bill]

Great information, thank you, do you know if the hwh goes through the same manifold there as the level low? Trying to think why hwh works but level low doesn’t. We can’t even raise it manually from level low controls

[Art]

key on engine not running–ck power to center coil on your stack

[Jerry]

tried to do that and showed no power, but didn’t want to take plug apart to get better contact with multi-meter (I just king of plugged the coil mostly in and tried to get a reading off the blades and it was 0). Could it just be the knob up by the driver?

[Archived]

Great post Jon, you covered a lot. It’s a keeper.

[Bernie]

no power=no relay -valve open to supply air. on stock prevo system power comes from Ign switch pole(on switch) don’t know how hwh changed this.

[Tad]

Verified no power when key on, also breaker in compartment above isn’t tripped, I guess have to work upwards from there to knob,