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 air conditioner activation if coolant pressure is too low or high;- the engine control unit that excludes compressor operation in accordance with engine management mode; e.g. in the case of high engine temperatures or high engine load (sudden acceleration);If the compressor is enabled and the engine started, the manual ventilation does not go below a minimum valueFor more details See descriptions 5040 AIR CONDITIONING CASING AND COMPONENTS