V Class self levelling suspenion and battery access

Hi Folks.
Firstly if this group does not cover newer vehicles I appologise and would appreciate a pointer to a more relevant newsgroup if there is one.
I recently purchased a RHD VClass with a wheelchair lift (rear) on behalf of a relative.
The rear suspension is self levelling and I believe pneumatic (or may possibly be hydraulic) failed last week with a warning light on the dashboard. It has blue and yellow pipes going to what look like bellows on the rear swinging arms. To me they look like air pipes.
Has anyone had experience of this system?
If you have, any information would be greatly appreciated. There is manifestly a fault as the suspension is right down.
But I also have some specific questions if anyone knows the answer.
Is the compressor 12V Is it a simple +12V and ground connection? or two wire 0V and +12V If I applied 12V to it from a battery to test it (briefly) would I be likely to damage anything ? Where is the relay which operates it located? Under the passenger seat ?
Where is the control module located? Under the passenger seat?
I have tried moving the seat as far forward as possible but suspect there may be a mechanism to allow it to tilt further forward or something as it would be nigh impossible to remove the battery otherwise or do I have to remove the seat. If I do how is that done easiest?
There are sensors on the rear swinging arms are they simple switches maybe with top and bottom positions or potentiometers or what?
Any help greatly appreciated. My experience with other vehicles is that sometimes supposedly irreparable items can be repaired by someone practical with a good workshop.
TIA
David
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Hi. Can't remember where the relay is, though I think it will be in the relay block under the passenger seat. The control unit is behind the right/rear panel. As you open the tailgate. The compressor and valve unit are on the left of the car, about half way down. The blue and yellow air pipes go from the 2 valves (left/right) to the air bellows. The level sensors are potentiometers. If you disconnect the plug connectors to the valves and compressor you can check voltage at the compressor. Or you can power the compressor with 12v and an earth. I've seen a few wheelchair conversions where the lift frame traps the suspension loom that runs under the car. After a while the wires short out or break. The air pipes from the compressor and valves are a quick release design. Hold the collar in then pull the pipe out.

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Hi Lee, thank you for the information I am going to get the vehicle and have a look at it again before I book main dealer. If anyone else has anything to add please feel free.

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For information only
I hope I have sorted the problem. Because of my lack of familiarity with the vehicle and systems it took a while.
I dropped the compressor and valves so I could see what what. All the electrics plug into the compressor, solenoids and what I take to be the pressure regulator. On this model compressor was 12v as were the solenoids and pressure regulator.
12V was carefully applied to the compressor via a fused cable (10 Amp) which sounded like it was working. I disconnected what I take to be the resevoir above it which was under pressure. Quite a lot of moisture came out. There seemed to be some air flow from the compressor but not as much as I was expecting. The solenoids were checked by applying 12V to them and listening for a click. The solenoid feeding the right bellows did not appear to be working. The ohmeter read between .8 and 3 MegaOhms virtually open circuit, the working solenoid gave 26 Ohms. I took the solenoid off to see if it was repairable but sadly it was a sealed. I did unseal but repair was not possible so a new pair was ordered.
I wanted to confirm that this was indeed the fault or the only fault and took the sliding valve out of the defunct solenoid and replaced the casing I cut the wires near the dead solenoid and connected a coil from another air valve off another 12V vehicle with 36 Ohms resistance in its place. The replacement solenoid wasn't doing anything other than loading the electric circuit. The solenoids were put back in circuit the other connections reconnected.
The ignition was turned on, at first nothing happenned but when the manual button to raise the suspension was pressed for a few seconds the compressor kicked in and the suspension rose, the warning light went off and the compressor stopped. The car seems to drive OK. I intend to use it for a couple of short journeys until the parts arrive next week. Does anyone think it will damage anything (journey length 2-3 miles low speed smoothish roads with heavy wheelchair user on board)
It would seem that the electronics can sense when a solenoiod is open circuit and shut the system down.
New valves 90 inc VAT not as bad as it might have been.
I only have the heated rear window, roof lining, thermostat, arm rest and failed lamp that I can't find to sort out now.
The front passenger seat has to be removed to improve access to the battery and wiring, 4 torx headed bolts on the runners , bit heavy to lift out and watch out it doesn't short the battery but quite easy to do.
I personally think the compressor is under powered for what it sometimes has to do.
Lee thank you for your advise, the bit about disconnecting the air pipes in particular that saved me a lot of hassle.
David
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