A method for controlling an air conditioner comprising an evaporator, a condenser and a compressor, the method comprising the steps of: providing at least one predetermined operational value including compressure and/or temperature values of the compressor, said predetermined operational value defining a safe area; measuring operational values of the compressor; comparing the measured operational value to the predetermined operational values; if the operational value of a current driving mode of the compressor does not fall inside the safe area, controlling variable means to ensure that the compressor runs in the safe area, wherein if the air conditioner is in either of a cooling or heating mode, at least one of sucking compressure (Psc) and discharge compressure (Pdc) of the compressor is measured, wherein if the sucking or discharge compressure measurement (S1001; S1101; S1301; S1401; S1601; S1701; S1801) is within a range between first and second predetermined sucking compressure values (Ps1, Ps2) and a range between first and second predetermined discharge compressure values (Pd1, Pd2), the compressor is allowed to keep the current driving mode (S1006; S1306; S1406; S1606; S1706; S1806), wherein if the current driving mode of the compressor is in an unstable area and not in the safe area, variable means of an inverter compressor (S1104; S1404; S1704; S1804) or variable means of a constant-speed compressor (S1108; S1408; S1708; S1808) are controlled, respectively, characterized in that if the inverter compressor (S1104...) is concerned, operational frequency of the compressor (S1104...), indoor/outdoor EEV, and air flow of indoor/outdoor fan is controlled in order to force the compressor (S1104...) to be running in the safe area, wherein if the constant-speed compressor (S1108...) is concerned, turning on/off of the compressor (S1108...), indoor/outdoor EEV control, and air flow control of indoor/outdoor fan is performed in order to force the compressor (S1108...) to be running in the safe area. providing at least one predetermined operational value including compressure and/or temperature values of the compressor, said predetermined operational value defining a safe area; measuring operational values of the compressor; comparing the measured operational value to the predetermined operational values; if the operational value of a current driving mode of the compressor does not fall inside the safe area, controlling variable means to ensure that the compressor runs in the safe area, wherein if the air conditioner is in either of a cooling or heating mode, at least one of sucking compressure (Psc) and discharge compressure (Pdc) of the compressor is measured, wherein if the sucking or discharge compressure measurement (S1001; S1101; S1301; S1401; S1601; S1701; S1801) is within a range between first and second predetermined sucking compressure values (Ps1, Ps2) and a range between first and second predetermined discharge compressure values (Pd1, Pd2), the compressor is allowed to keep the current driving mode (S1006; S1306; S1406; S1606; S1706; S1806), wherein if the current driving mode of the compressor is in an unstable area and not in the safe area, variable means of an inverter compressor (S1104; S1404; S1704; S1804) or variable means of a constant-speed compressor (S1108; S1408; S1708; S1808) are controlled, respectively, characterized in that if the inverter compressor (S1104...) is concerned, operational frequency of the compressor (S1104...), indoor/outdoor EEV, and air flow of indoor/outdoor fan is controlled in order to force the compressor (S1104...) to be running in the safe area, wherein if the constant-speed compressor (S1108...) is concerned, turning on/off of the compressor (S1108...), indoor/outdoor EEV control, and air flow control of indoor/outdoor fan is performed in order to force the compressor (S1108...) to be running in the safe area.