V Class self levelling suspenion and battery access

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David - 26 Jan 2006 15:26 GMT

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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Lee - 26 Jan 2006 19:52 GMT

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.

> Hi Folks.
>
[quoted text clipped - 39 lines]
>
> David

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David - 27 Jan 2006 09:09 GMT

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.

> Hi. Can't remember where the relay is, though I think it will be in the
> relay block under the passenger seat.

Any idea how to improve access to this area?
Do I have to remove the seat ?

The control unit is behind the

> right/rear panel. As you open the tailgate.

Are the panels on plastic fasteners which break when cold

> 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

Found all that. Any idea how easy is it to remove (car not to hand at
present)
Is there a resevoir and is it with the compressor (maybe above it?)

The level sensors are potentiometers.
Any idea whether there are also limit/end stop contacts within them?

If you disconnect the

> plug connectors to the valves and compressor you can check voltage at the
> compressor.

Do I need to disconnect the plugs to the valves. There is a two pole plug
going to the compressor I think I can disconnect that can't I ? Am I
likely to do damage if I connect wrong way round (briefly) as there was no
indication apparent as to which is +Ve I have tried looking for volts from
the wiring harness to the compressor but there wasn't any apparent. I did
have the rear of the car jacked up on one side only so I think that may mean
the level sensors weren't requesting air as it would be interpreted as going
over a bump on one side. Any thought?

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.

This adaptation is a Ricon wheelchair lift at the back I can't think that
any of the suspension harness goes near it but will check. I thought I had
found the cause last week when I spotted a broken cable but that was to an
ABS sensor. If anyone knows of any specific location I should inspect please
let me know.
There is the interesting situation that the SRS light occasionally comes on,
seemingly when it is on the driver side mirror adjustment does not work.

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.

Thank you for the input any pointers would be appreciated even if they
relate to other models

David

>> Hi Folks.
>>
[quoted text clipped - 39 lines]
>>
>> David

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David - 27 Jan 2006 21:20 GMT

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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