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Hi, did you also replace the compressor fuse?
Ok, if you bypass the relay will the compressor turn on?
Ok, but the compressor will not turn on when you start the car or when you press the button to raise the car, is that correct?
If you only have rear air suspension there will not be a switch on the dash.
On all wheel air suspension the switch is next to the hazard switch.
Click on the link below.
If the compressor will not turn on you will need to get the car connected to any Mercedes scan tool that can read and erase fault codes in the Airmatic control unit. Once the fault codes are erased the compressor will turn on.
Did you go into the Airmatic module and erase the codes or did you only erase the codes in the engine control module?
If your scan tool cannot select the Airmatic module it cannot erase the codes.
What brand is the scan tool?
I'm not familiar with that tool. As long as there is power to the relay and the compressor runs when you bypass the relay this should just be a matter of erasing the codes with a Mercedes scan tool. I am assuming that the level sensors at the rear are connected. Also make sure fuse 32 and 53 in the rear fuse box are good.
I'd go to the dealer or to an independent who has the Mercedes SDS or an equivalent factory level tool.
We've basically gone through the trouble tree. Power to the relay, power to the control unit, compressor runs when bypassed. All that points to no activation by the Airmatic control module.
With the factory scan tool you can activate the compressor to test the entire circuit.
I understand. What usually happens is when the air bags fail it causes the compressor to run excessively. The Airmatic control unit will turn off the compressor and set a fault code when that happens. The compressor will not start again until the codes are erased.
Also make sure that your level sensors are connected properly.