Viano 639 air suspension problem...

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motocrosser334

New Member
Joined
May 7, 2019
Messages
4
Location
scotland
Car
Viano
Hey there folks...recently the red light for my air suspension came on...and over the next while i noticed the left hand side of the van slowly go down...the compressor come on briefly for like a second then stopped...it did this once or twice over the next week or so...
I took it to the local garage who told me it needed a new compressor and new module (from under jack beside rear right light cluster) from mercedes we were quoted £1200 for these 2 parts. I managed to get two second hand parts and fitted them...only to find it did not solve the problem...I tested both the old and newer compressors and these both worked...
When changing the compressor i also changed over the other boxes that splits the air for left and right airbag...the guy i bought these from assures me that all the parts worked when he took them off his van

I only have 9v at the plug going onto the compressor, which i thought was strange...is this where i have the problem...I cant find any other fuses or relays, but thought if something was blown i wouldnt be getting any voltage at all...?

I have a red light at the switch in the boot, but nothing happens when i press it

Is the fault coming from the module...or some other place...?

Ive considered swapping out to springs but thought id need shock absorbers to go with it, but couldnt see any fixings for them...

Any help greatly appreciated...im a wheelchair user and missing the use of the van and side lift

Thanks

I see mentions of STAR machines...would this be needed to initiate the system since dead flat...and is that a Mercedes job or local garages have such tools? :)
 
Last edited:
Hi there.
I am by no means an expert but having had the same problem with mine I'll try & help. It could be multiple things but clearly there is a leak as the van drops just on the left hand side(mine had totally collapsed & the compressor wasn't working at all). That is the 1st thing the garage should have identified. Mine needed 2 new bags as they were original & badly cracked although only one side leaked. The compressors are designed to cut out if they run too long(mine had to be restarted on a Star machine but luckily it hadn't failed). 4000 miles later all is well(touch wood)if passengers get in the van goes down & then gently rises up. My buttons for raising & lowering don't work. So the garage need to find out where it is leaking & fix that(they can do it with soapy water if there are no codes showing on Star). I would have thought 9v is odd but my compressor hardly ever works as my load is constant, you should only hear it briefly when it is correcting the height. There don't seem to be many Viano owners on here & people seem reluctant to help given that the air suspension works the same on more Mercs than just the Viano. Try searching on here as the answer might be in the archives but 1st thing is to find out why it is leaking. Hope this helps a little.
 
Hi there.
I am by no means an expert but having had the same problem with mine I'll try & help. It could be multiple things but clearly there is a leak as the van drops just on the left hand side(mine had totally collapsed & the compressor wasn't working at all). That is the 1st thing the garage should have identified. Mine needed 2 new bags as they were original & badly cracked although only one side leaked. The compressors are designed to cut out if they run too long(mine had to be restarted on a Star machine but luckily it hadn't failed). 4000 miles later all is well(touch wood)if passengers get in the van goes down & then gently rises up. My buttons for raising & lowering don't work. So the garage need to find out where it is leaking & fix that(they can do it with soapy water if there are no codes showing on Star). I would have thought 9v is odd but my compressor hardly ever works as my load is constant, you should only hear it briefly when it is correcting the height. There don't seem to be many Viano owners on here & people seem reluctant to help given that the air suspension works the same on more Mercs than just the Viano. Try searching on here as the answer might be in the archives but 1st thing is to find out why it is leaking. Hope this helps a little.

Hey there. Thanks for the reply. Well I have swapped the module and the compressor...regardless of whether the airbag is leaking I'm thinking the compressor should be coming on. But I don't seem to be getting the power to start the compressor. I connected a 12v supply to the comp and it came on, tho the airbags didn't seem to inflate...I'm wondering what the STAR machine does...does it restart the system, compressor...the level sensors...what does the STAR machine influence?
Perhaps since I've changed these parts it's only this restart I need?

Bit lost for options now. I have other airbags so that's not a big deal.

Is the STAR machine a mercedes piece of equipment, or do smaller garages work them?

Thanks
 
Either a MB dealers or a Mercedes Independent ( Indi ) will have a Star system
 
1st thing is to find the leak. Fix the leak & you can at least use it. I was considering springs but they are still expensive & you need brackets as well. I'm not electrically minded but mine wasn't working & it had to be reset/forced to work on a Star machine(this could be what's happened to yours). A Star machine is a diagnostic computer that reads the "brain" of your car & shows you all the fault codes as well as being able to reset the codes. Mine had no codes showing although it wasn't an MB machine. A Mercedes Independent will have a code reader of sorts & then there are the DIY sort too. Have you a good Merc Indie near you? You know the compressor works which is good as that's the expensive bit. To my non expert mind you just need to find the leak & then go from there. Can anybody else help? I've just been reading an E class saga from Baldbloke but he seems to have fixed his & I think the system is the same.
 
Hey there. Thanks for the reply. Well I have swapped the module and the compressor...regardless of whether the airbag is leaking I'm thinking the compressor should be coming on. But I don't seem to be getting the power to start the compressor. I connected a 12v supply to the comp and it came on, tho the airbags didn't seem to inflate...I'm wondering what the STAR machine does...does it restart the system, compressor...the level sensors...what does the STAR machine influence?
Perhaps since I've changed these parts it's only this restart I need?

Bit lost for options now. I have other airbags so that's not a big deal.

Is the STAR machine a mercedes piece of equipment, or do smaller garages work them?

Thanks

I’m certainly not an expert on your van, but...
Even though you managed to power up your compressor briefly, there’s probably a solenoid valve unseen on the top of your air springs. This possibly isn’t getting the signal to allow air into the bags as everything air bag related tends to be regulated by its dedicated ECU. By powering up the compressor it hasn’t necessarily managed to initiate all the other requirements.
Check for pipe leaks, leaks at pipe junctions and where the pipe enters the air bags using plenty of soapy water. If no leaks take it to someone with Star diagnostics [emoji1303]



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Any good independant Merc specialist will have Star Xsentry. It is an MB specific diagnostic kit but availalble to Indies.

I might have contributed earlier but my thoughts are no more than guessing.
I might expect the bags to leak slowly if not in use for a while, but the level sensor should see that on start up and re inflate, using the compressor clearly.
I've noticed that the compressor won't start until the vehicle is on the move, perhaps 10mph??

Alternativley the buttons inside the tailgate can be used at standstill.
I find that pressing the LED button for a few seconds switches to manual. The up / down should then work.

In your case I might suspect the level sensors at the rear, underside, on the suspension. I've seen these rust, freeze, and the plastic arm break by the suspension movement. That was for headlight levelling on a C Class but same(ish) set up.
I don't know if the Viano system operates valves for left / right if one side is down.
I don't know if this locks out, as suggested, by continous operation / too many tries.
I don't know if this would auto reset when working correct again, I don't see why not but there are stranger things on Mercs.
The 9 volts does sound strange, is the battery healthy? Clearly the fuse (Fuse rail F34 no 30, 40 amp if like mine) hasn't blown. But I would check for good connection at it, furring blades for example. Sorry I didn't trace which relay might be the culprit.
 
As suggested above: check the arm on the level sensor hasn’t corroded off. On my car it’s central above the rear axle. A bit of a ***** to get at.


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I believe the sensor to be ok, as we had to move it when taking the plate with the compressor off...but could get it back up on the ramp and check them again.

I wonder if the reset would kick it into working...or show up where problem was...
 
The electrical connection to the compressor can be a bit iffy. I need a cable tie around mine even with a new compressor to get it to run.
 
Hey folks...just thought id update my status...

Well after the first garage saying i needed £1200 parts, and buying second hand which made no difference, took it to another local garage who had an ex mercedes mechanic...and was told i needed a height level sensor as it was broken...changed that and away it went. Total bill came to £190+ vat...with the mercedes sensor being £120 of that. Just as well i didnt say go ahead with the new comp and module...
I would of changed the second height module as he said it would probably be next to go but there wasnt 2 in stock...but will know for future

Thanks for all the ideas and advice ;)
 

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