The special button (ice symbol) on the climate control system control unit switches on the air cooling and dehumidification circuit, activating the air conditioning compressor.The above button enables the operation of the air cooling circuit, but the actual compressor activation is also dependent upon the activation of:- the linear sensor, located on the coolant circuit that locks the air conditioner activation if the coolant pressure is too low or high;- the engine control unit that excludes the compressor operation in accordance with the engine management mode; e.g. in the case of high engine temperatures or high engine load (sudden acceleration).For more details, See descriptions 5040 AIR CONDITIONING CASING AND COMPONENTSThe compressor supply circuit is controlled by a specific relay and protected by a specific fuse both located in the engine compartment junction unit.