If the suspension hasn’t resettled downward…and/or you don’t constantly hear the compressor running…there’s probably nothing wrong other than you hadn’t driven the vehicle for awhile.
When you did start her up…the suspension had dropped slightly so the compressor turned on and corrected the suspension height. That’s what the system is designed to do. Since temperature can affect the air in the springs…since the car hadn’t been driven in a month…the discharge valve probably released some of the air in the one or both of the springs (especially if the ambient temperature changed drastically in the month it was sitting undriven):
Discharge valve
The discharge valve is activated by the EHC control unit. The air escapes from the solenoid valve block via the discharge valve through the air drier.
The pressure limitation function of the discharge valve limits the pressure in the air supply system as follows: Maximum pressure 13.5 bar (temperature-dependent tolerance +5 to + 6.5 bar = breakaway moment if discharge valve not used for a longer period)
Air Supply (compressor)
- Electric motor
- Compressor
- Air drier
- 2-pin plug connection for discharge valve
- 2-pin plug connection for electric motor
- 3-pin plug connection for solenoid valve block
- Valve block
My e53 X5 has rear SLS and it’s always running the air compressor for various scenarios…especially if it hasn’t been driven in a while….and there’s nothing wrong with the air bags.
Again, if the compressor kicked on after not driving the vehicle for a month…and the suspension appears to be the correct height and the compressor isn’t continuously running to pump the suspension back up…then nothing is wrong except for not driving the vehicle enough.
