You need to have it plugged in to a diagnostic machine. The car needs to be told it is not on airbags anymore then the switch becomes useless and the compressor (if still there) will stop intermittently trying to pump them up. Try your local garage, mine charged me £20 to do this and also read any other fault codes whilst it was plugged in after doing some other work for me, i think it would usually be £30-40.