Air suspension question

[uteman]

Before I start some trouble shooting someone may have the answer. Twice recently my TD-6 indicator panel has read: "Air Suspension Inactive".
The car stays in normal ride height.
I put my Faultmate on it and got the following error reading: "RESERVOIR PRESSURE STATIC WHEN FILLING, (CURRENT, INTERMITTENT)."
If I clear the fault it works perfectly for many days and the car sits up correctly on all four corners.
I have not yet attempted any trouble shooting but that almost sounds like a compressor issue but you may have other experience that will cut the searching short.

[Homestar]

Sounds like a compressor to me. Do you notice it running longer than it used to some of the time. Only other thing I can think of is a pressure sensor not reading correctly, but that may bring up a separate fault - not sure.

The compressors are rebuildable as well if it is that and you don't want to fork out for an entire unit.

[justinc]

certainly sounds compressor related, but i would check the compressor 'on' signal and actual chamber pressures to check this diagnosis.

jc

[uteman]

Sounds like a compressor to me. Do you notice it running longer than it used to some of the time. Only other thing I can think of is a pressure sensor not reading correctly, but that may bring up a separate fault - not sure.

The compressors are rebuildable as well if it is that and you don't want to fork out for an entire unit.

Do you know where I can get a compressor rebuild kit.

[Homestar]

Do you know where I can get a compressor rebuild kit.

Tis one shows that it is for the L322. There are others come up from time to time that have a new piston and other stuff, but they are over £100. For the price, if this fixes it - even for a while, you would be ok IMO.

WABCO AIR SUSPENSION COMPRESSOR PISTON RING REPAIR FIX KIT | eBay (http://www.ebay.co.uk/itm/WABCO-AIR-SUSPENSION-COMPRESSOR-PISTON-RING-REPAIR-FIX-KIT-/321130115690?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item4ac4d8b26a)

Cheers - Gav

[harlie]

...
got the following error reading: "RESERVOIR PRESSURE STATIC WHEN FILLING, (CURRENT, INTERMITTENT)."



this fault is recorded when the ECU provides a switch signal to the compressor and air pressure in the tank remains constant. So the ECU knows the compressor should be running, and knows that pressure hasn't changed, we assume, with good reason, that the compressor isn't running.

As justinc mentioned, check the compressor is receiving 12v first (ECU doesn't check that), then check the pressure in the system (make sure pressure sensor is ok), then rebuild compressor. There is a real possibility that the compressor is fine and not receiving power, or the sensor is not good (this one is rare).

[uteman]

this fault is recorded when the ECU provides a switch signal to the compressor and air pressure in the tank remains constant. So the ECU knows the compressor should be running, and knows that pressure hasn't changed, we assume, with good reason, that the compressor isn't running.

As justinc mentioned, check the compressor is receiving 12v first (ECU doesn't check that), then check the pressure in the system (make sure pressure sensor is ok), then rebuild compressor. There is a real possibility that the compressor is fine and not receiving power, or the sensor is not good (this one is rare).

The compressor obviously runs as if I clear the fault with my faultmate the car will raise and lower for a day or two although it is a more than a bit slow when I try for "Off-Road" height. Your input is valued.
At this time my schedule has not allowed any time for further trouble shooting.

[philmoon]

can you guys tell me will this fit the earlier compressor ... the donut style looking thing ...
Thanks again you guys are the best

[philmoon]

sorry I meant the kit on ebay that is linked... if not what options are available to me ???

[uteman]

The compressor obviously runs as if I clear the fault with my faultmate the car will raise and lower for a day or two although it is a more than a bit slow when I try for "Off-Road" height. Your input is valued.
At this time my schedule has not allowed any time for further trouble shooting.

I got a few moments to investigate the car some more today.
Firstly I cleared the fault with the "Faultmate" then did the following whilst car was in driveway.
1. Removed cover from compressor just in case it did not run and I wanted to do further checks.
2. Lift to Off-Road height and back to normal road height and all went OK on several such movements.
3. Lower to the entry/exit level and this went OK but what was interesting was that each time I raised it to normal level the indicating light would stop blinking indicatng that the car had reached the selected height which it clearly had. Then after a few seconds the compressor would start to run again for some time even though the car had already reached road height and the compressor had stopped.
4. This made the Faultmate error reading of "Resevoir pressure static when filling" make some sense as it seems to me that the reservoir was already at pressure but something was giving a signal for it to run again.

Happy to receive any feedback

[Maxintosh]

I'm guessing a little here, but let me see if we can check the logic of what is going on...

The reservoir fills the air bags, not the compressor directly. The compressor will fill the reservoir when the pressure switch reaches a certain level, and then cut out at a certain higher level, just like workshop air-compressor does.

If the reservoir is holding 'static pressure' then there is no leak in the system, if, however, there is a leak, then the pressure in the reservoir will drop. Leaks could be hoses, seals, holes in bags, loosened nut fittings, or back from the compressor.

To receive the message "Reservoir pressure static when filling" I am assuming that either there is a leak at a comparable rate to that the air-compressor can deliver, or the air compressor is not providing additional air pressure to the reservoir. I.e. most likely that the air-compressor needs a rebuild, or, that an o-ring lets go at a pressure similar to the steady state, so when the pressure rises, the leaks start, but at a lower level, it is not enough to escape.

Anyway thats my 2c worth.

[uteman]

I'm guessing a little here, but let me see if we can check the logic of what is going on...

The reservoir fills the air bags, not the compressor directly. The compressor will fill the reservoir when the pressure switch reaches a certain level, and then cut out at a certain higher level, just like workshop air-compressor does.

If the reservoir is holding 'static pressure' then there is no leak in the system, if, however, there is a leak, then the pressure in the reservoir will drop. Leaks could be hoses, seals, holes in bags, loosened nut fittings, or back from the compressor.

To receive the message "Reservoir pressure static when filling" I am assuming that either there is a leak at a comparable rate to that the air-compressor can deliver, or the air compressor is not providing additional air pressure to the reservoir. I.e. most likely that the air-compressor needs a rebuild, or, that an o-ring lets go at a pressure similar to the steady state, so when the pressure rises, the leaks start, but at a lower level, it is not enough to escape.

Anyway thats my 2c worth.

Maxintosh: I have already ordered a new kit for the compressor and will rebuild it when I get home from overseas on 26th June and report further. I just cannot hep but think that there is a gremlin in a pressure sensor somewhere but first things first and then we shall see.
When I was going through the tests that I did today the performance of the compressor did seem adequate but as I said, we shall see.

[harlie]

I got a few moments to investigate the car some more today.
Firstly I cleared the fault with the "Faultmate" then did the following whilst car was in driveway.
1. Removed cover from compressor just in case it did not run and I wanted to do further checks.
2. Lift to Off-Road height and back to normal road height and all went OK on several such movements.
3. Lower to the entry/exit level and this went OK but what was interesting was that each time I raised it to normal level the indicating light would stop blinking indicatng that the car had reached the selected height which it clearly had. Then after a few seconds the compressor would start to run again for some time even though the car had already reached road height and the compressor had stopped.
4. This made the Faultmate error reading of "Resevoir pressure static when filling" make some sense as it seems to me that the reservoir was already at pressure but something was giving a signal for it to run again.

Happy to receive any feedback

Either, the compressor is not handling higher pressure which a rebuild will fix
OR, the pressure switch is sticking or stuffed, not reporting change above a certain pressure (top of my list now)
OR there is a leak. You should notice the compressor run as soon as you start up, trying to recover lost pressure when the car is off. Should be easy to rule out/confirm.

There could be a problem with the pressure switch wiring, the ECU may be loosing signal, check the plug, clean and reseat - long shot. I would expect the "Pressure dropping when filling" or Comms error fault in this case (and for a leak).

Think like a computer for a sec, remember we can only 'think' about the code that was fed to us by the original developers. The "[something is wrong] when filling" error is logged because the ECU has instructed the compressor to fill, and [something is wrong] condition has been met while the fill instruction is active. So the "something was giving a signal for it to run again" IS the ECU. For that fault to be logged the ECU must have turned the compressor on - if it didn't you would have "compressor temp rising while not filling" fault.

[uteman]

Tis one shows that it is for the L322. There are others come up from time to time that have a new piston and other stuff, but they are over £100. For the price, if this fixes it - even for a while, you would be ok IMO.

WABCO AIR SUSPENSION COMPRESSOR PISTON RING REPAIR FIX KIT | eBay (http://www.ebay.co.uk/itm/WABCO-AIR-SUSPENSION-COMPRESSOR-PISTON-RING-REPAIR-FIX-KIT-/321130115690?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item4ac4d8b26a)

Cheers - Gav

BACICAT: After confirming that WABCO do not supply any service items for the compressors I obtained the kit that you told me of through Ebay.
Total cost with postage was something like 29 UK Pounds or 47 Aussie dollars.This compares to $868 plus GST from the local dealer for a replacement compressor.
I removed the compressor and fitted the new piston ring in short time which would be even shorter should I ever do it again.
Result: all seems perfect with the raise to off-road height being much faster than it has been in a long time. No messages coming up on display anymore so all A OK.
Thanks to all who submitted replies and advice and don't hesitate to build your compressor as it simple.

[Maxintosh]

Well done uteman, thats bloody good to know