Should i hear the EAS valves clicking when ignition is off?

In the last week the back of the disco has started sinking over night, mainly on the one side, can't work out if the otherside is going down too or if its just the extra weight on it. On start up it level straight away. I've checked with soapy water the bags, pipes and connection to compression for leaks and there is nothing (although cant see where pipes connect to bags. But while i was under there i noticed a noise and traced it back to the compressor box, and turns out its one of (or both) of the EAS valves making the noise. The noise carries on with the ignition off and for the entire 30minutes i was looking at. Should it do this, or does it sound like it fubared and releasing the air from the system???