Help with problem with Airmatic suspension on W212 E300

[themadsinger]

Friend of mine has a 63 plate E300 estate which has airmatic suspension on the rear (only I understand). Whilst his Mrs was driving it, it went down on the back completely. NO message on the dash. When the car is switched off and back on it says vehicle is rising but it doesnt rise and it doesnt sound like the compressor is firing up.

We have checked the relay and that sounds to be clicking in (checked with a multi-meter and got 6V on the switch supple) but there is no 12V feed across the relay. Checked the internet and it says there are 2 airmatic fuses - one in the front fuse box (no 12) and one in the rear fuse box (no. 68) but have checked both of those and they are fine. Have also checked with multi meter and there doesnt need to be a 12 V feed into the 68 fuse (which has continuity with the input feed to the relay supply), so it seems there is an issue with that 12V feed. If we hook the compressor to a 12V feed it runs OK and seems to have reasonable pressure behind it. Mate tried putting an airline to the outlet feed to see if that would inflate the suspension but wouldnt which suggests to me that the inflation valves were not open in the valve block (this was tried with the car running and the "vehicle rising" message on the dash which means that the compressor should be energised and the supply valves open. This also suggests therefore that the solenoids on the valve block are not being powered and hence a supply problem.

Can anyone suggest where to look next. Having checked the two fuses which are supposed to be for the auirmatic and both fine cannot understand why there is no supply. Have checked the control module in the passenger foot well and there is no fuse (that we can see) in there.

Any help would be much appreciated.

Thanks

 

[JDD]

Hi just reading your thread although it’s a little bit old, I’ve got exactly the same problem just wondering whether or how are you solved it
regards GD

 

[themadsinger]

Hi just reading your thread although it’s a little bit old, I’ve got exactly the same problem just wondering whether or how are you solved it
regards GD

Hi Mate,

Sorry to say havent gotten to the bottom of it YET..., but have made some more progress....sort of. We put 12V to the compressor and it ran but quickly slowed down, so we decided that the valve manifold wasnt opening. SO we put 12V to that as well as it pumped up the suspension. left the power disconnected from both the compressor and the manifold and, although it gave a fault indication, the suspension stayed up and the car was (and is useable). After leaving it a day or so and the suspension staying up, we reconnected the power to both the compressor and the valve manifold and at some point (not sure when) the suspension went down again!!!! Think it went down when the vehicle was stationary, which is weird as that would indicate a leak but why would that no happen when the power to the compressor and manifold was disconnected (if you have any ideas on that let me know).

Was busy last weekend so we didnt have any time to look further and since we had a way to have the suspension up wasnt as high a priority as it was (indeed my mate was talking about rigging up a switched 12V feed to the compressor and valve manifold so he could just fire it up if it dropped but I suggested better to try to actually solve it). Going to check the sensors for damage and then he knows someone who has a snap-on reader so going to see what fault codes there are to see if that casts any light.

if you have any thoughts, or have done anything else to progress it, let me know. if you want any guideance on getting to the compressor etc, again let me know.

 

[MercedesDriver]

Probably snapped one of two level sensors. Factory fitted ones are plastic and very brittle so it might be that one got frozen and with the slightest movement just snapped. Tell Mrs it’s not her fault.

 

[themadsinger]

Probably snapped one of two level sensors. Factory fitted ones are plastic and very brittle so it might be that one got frozen and with the slightest movement just snapped. Tell Mrs it’s not her fault.

Thanks. Did wonder that but why would snapping one of the sensors result in (a) both sides dropping and (b) there being no power fed to either the compressor or the valve manifold even when car says vehicle rising? and also how does it know the car needs to rise but doesnt give a vehicle too low fault?

 

[MercedesDriver]

Thanks. Did wonder that but why would snapping one of the sensors result in (a) both sides dropping and (b) there being no power fed to either the compressor or the valve manifold even when car says vehicle rising? and also how does it know the car needs to rise but doesnt give a vehicle too low fault?

It happened to me exactly as you have described
See this:
S212 completely sagged but no messages | Wheels, Tyres, Brakes & Suspension

 

[JDD]

Hi Mate,

Sorry to say havent gotten to the bottom of it YET..., but have made some more progress....sort of. We put 12V to the compressor and it ran but quickly slowed down, so we decided that the valve manifold wasnt opening. SO we put 12V to that as well as it pumped up the suspension. left the power disconnected from both the compressor and the manifold and, although it gave a fault indication, the suspension stayed up and the car was (and is useable). After leaving it a day or so and the suspension staying up, we reconnected the power to both the compressor and the valve manifold and at some point (not sure when) the suspension went down again!!!! Think it went down when the vehicle was stationary, which is weird as that would indicate a leak but why would that no happen when the power to the compressor and manifold was disconnected (if you have any ideas on that let me know).

Was busy last weekend so we didnt have any time to look further and since we had a way to have the suspension up wasnt as high a priority as it was (indeed my mate was talking about rigging up a switched 12V feed to the compressor and valve manifold so he could just fire it up if it dropped but I suggested better to try to actually solve it). Going to check the sensors for damage and then he knows someone who has a snap-on reader so going to see what fault codes there are to see if that casts any light.

if you have any thoughts, or have done anything else to progress it, let me know. if you want any guideance on getting to the compressor etc, again let me know.

Hi thanks for your reply
my indie has been COVID bound and could only come yesterday
I had put in new compressor fuses 12 & 68 were ok relay clicking so I was glad to see him
After diagnosis he found 40amp fuse had gone, so relay had 12volt for switch but not for compressor motor, found it in front fuse unit, by the battery, it’s a sod to get to and typically MB will only sell complete fuse box, so I sourced second hand one off eBay. He’s coming back next week to fit but we need to find why it blew, hopefully the old compressor went bang. More info next week
Oh and he’s replacing the complete air lines as the S212 continually had a “ soggy bottom “
regards JD