on a p8 esc cos,what exactly does the chip have to do with regards to the aircon system? as far as i can make out there are 2 pins on the ecu,pin 21 from the pressure switch and pin 12 which is an earth from relay no11?i know the ecu increases the idle speed slightly to compensate for the aircon system running but how does the earth from relay11 work? any experts out there? think im getting there now