Method for operating a pneumatic system of a vehicle

A method for operating a pneumatic system of a vehicle with an electronically and/or pneumatically controlled compressor, the compressor having a normal mode which supplies compressed air to the pneumatic system, the normal mode being switched off or the compressor being in an idle mode when not supplying compressed air, said method comprising:

• detecting an ambient temperature (T_Umg) exterior to the pneumatic system and continuously comparing the ambient temperature (T_Umg) with a predetermined target temperature (T_Ziel),
• detecting a risk of freezing if the ambient temperature (T_Umg) reaches or drops below the predetermined target temperature (T_Ziel),
• activating a cold mode upon detecting the risk of freezing, wherein in the cold mode in addition to the normal mode the compressor supplies compressed air that is fed to components at risk of freezing of the pneumatic system to heat them, the compressed air being additionally provided to the pneumatic system or discharged into the surroundings, wherein a variable switch-on duration (ED_zus) of the compressor is variably controlled in the cold mode if the ambient temperature (T_Umg) is within a predetermined ambient temperature range and is determined depending on a temperature difference (ΔT) between the ambient temperature (T_Umg) and the predetermined target temperature (T_Ziel), the switch-on duration (ED_zus) of the compressor being a fixed time period if the ambient temperature (T_Umg) is below the predetermined ambient temperature range, wherein the variable switch-on duration (ED_zus) increases from zero to the fixed switch-on duration (ED_zus) in proportion to the difference between the ambient temperature (T_Umg) and the predetermined target temperature (T_Ziel), and
• returning the compressor to the idle mode, or switching off the compressor, after the variable switch-on duration and after the fixed switch-on duration.