ARNOTT..is a great source of tech support on the air systems, with a live chat tech who is very knowledgeable about the options and systems. For example, I see warnings to never let the car off the lift with deflated air bags, so I was alarmed I needed to block up my W211 with a bad air pump to prevent damage to the shocks which are okay, just the air pump is bad..Arnott does not sell but only wholesales their products but their tech backup is awesome with engineers available. And they happily answered my questions immediately so hats off to those guys and IMO they make some awesome products.

My local MB dealer stocks the Arnott bags.

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Jim

The problem is with the arnott coil spring conversion which is much shorter and stiffer than the factory Mercedes coil springs.

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I installed the new arnott air pump and new relay- sold together. And checked fuses and cleared the error codes with the foxwell scanner which has commands to fill and empty each shock and run the pump..I can hear the solenoids clicking on commands, and yet the compressor does not come on.

The scanner tells me 'proceed according to the work' which seems to suggest something is omitted. As if the car must be lifted first. Arnott says to bench test the air pump which they should already have done, Yikes..I thought about it but decide not to.

Im going to the manual link you shared to read the details..fingers crossed.

the manual you shared, tjts1 is very detailed and helpful but I dont see any procedures for filling the air system specified. There IS a nice warning about wire chafe at the connection lines which with the pump vibration stands to reason, advice to check this. Id think this would cause a burned fuse but maybe its just an open circuit..

Still working away..This is a 'Just Ask' ad and they're sometimes helpful but Ive also had guys from there asking irrelevant questions and a waste of time.

So still working I get a 'procedure possible' message on the foxwell when trying to activate or test the air pump and yet when I try to fill the struts or raise the rear end level the relays in the rear click but there is no compressor running.

I would not jump the relay as we did on older cars without the computer systems..may generate weird issues with the software.

Check if you're getting power to the compressor plug.

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well when the relay closes I should be getting power, but if the compressor is not running then no, Id say it does not have power if the compressor is good and the connections are good. Or it would be running. Perhaps this is why Arnott said I should bench test the compressor. The system turns it on as needed, right? with low ride height, so it would be no. And the Foxwell tool tells me the voltage at the relay pins is 12 with the key off and then engine running it goes to 14 which is perfect.

Its tempting to manually jump the pins that control the compressor pump but again Im afraid that might mess up the software. Just jump that 40 Amp circuit with a light wire..On an older vehicle I would do it..

Did anyone say specifically what they were unhappy about?

It rides like ****.

W211 factory rear coil spring 8.5 coils.


Arnott coil spring conversion 6 coils. If you look carefully you'll notice the top and bottom coil are folded in and touching the previous coil so that last coil isn't doing any work under load. Its just there to seat the spring since theres no spring seat in the Arnott design.. That leaves 4 coil doing the suspension work.


This is the factory lower rear control arm designed to work with coil springs on the W211. The spring is seated inside the control arm so the entire length of the spring can work.


Airbag suspension cars used this control arm where a single bolt holds the air bag between the 2 forks.


Both Arnott and Strutmaster half ass the conversion by reusing the airbag control arm with a shorter coil spring and an aluminum block adapter in between. It sort of works but ruins the ride quality. If you're going to do a coil spring conversion, get the control arms designed for coil springs and proper springs to go with it.

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yes the coils are a poor man's fix. quick/dirty way to get on the road again. I may do it because perhaps Ive lost an ECU input to the circuits that actuate the air pump. Just wish I could run a switch and actuate it manually! Arnott nor anyone can suggest why all systems read good and yet the compressor pump will not come on.

Anyway I have a lot of ECU codes and this may be the issue..Could have been caused when the old air pump overheated and burned up..yet blew no fuse. The old relay was badly burned and had carbon in the points. Now replaced with the new one supplied with the pump..Easily fixed the old relay and it works fine but still needed replaced. Badly worn, contact points nearly gone.

Any expert tips appreciated.

Last update would be that the rear level sensors are showing no signal. Cleared a BUNCH of codes and they remain cleared. Low rear end continues to indcate as an error and the low car warning, do not drive..

I can only hope replacing the level sensors will cause the new air pump to kick in. $25 parts..

There's only one rear level sensor attached to the sway bar near the diff. I wonder if the problem is the suspension computer.

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Thanks for the details

Thanks for the details.

There isn't as dramatic of a coil count loss as one would think. The 8.5 factory coil is more like 6.5 because the first coil on each end is fully supported and therefor is dead.

It would be interesting to compare LB per inch of both springs.

A low coil count will give a higher spring frequency and a harsher ride compared to a high coil count of the same load rating. The real question is how much has ride quality suffered compared to a factory spring car

The other issue is how the front / real balance is affected and how the air bag shocks compare to steel spring shocks.

In the end, I'd use stock parts rather than the adapters.

There was a message from the foxwell I didnt understand, no communication from SY...Something. It does say the level sensor has no signal, maybe this is why and perhaps the burned pump took this computer out?

My update is that I was asked by Arnott to bench test the pump and I did without removing it. I pulled the power leads and with alligator clips supplied 12 volts and the pump ran great and pressurized the system until it popped the relief valve. No hissing anywhere, and its at nice full ride height! And no more error message. So something is indicating the car is level.

I didnt realize the suspension was controlled by a separate computer, I was going to order ride height sensor..I will pull the cover and give that a check and then look into the computer. Thanks again tjts1

Its just so nice to have it off the bump stops and not reading the error too low again!