Method for operating a coolant circuit for a vehicle air-conditioning system having - a coolant compressor, which can be adjusted by means of an actuation signal to control the compressor output, - a condenser or gas cooler, - an evaporator with an associated expansion valve, and - at least one pressure sensor (pT1, pT3) for measuring the coolant pressure on the high-pressure and/or low-pressure side of the coolant circuit, characterised in that a) the actuation signal ST of the coolant compressor is provided so as to increase over time from a minimum value (STmin) in order to generate a start-up phase of the coolant compressor, b) a control signal maximum value (STmax) and a control signal threshold (STsw) are provided where STsw < STmax, c) the actuation signal is limited to the control signal maximum value (STmax) if the actuation signal reaches the control signal threshold (STsw) and the measured high-pressure and/or low-pressure value (P HD, P ND) satisfies one of the following conditions: the high-pressure value (P HD) is lower than the high-pressure threshold (S P_HD), the low-pressure value (P ND) is higher than the low-pressure threshold (S P_ND), and/or the difference (ΔP) between the high-pressure value (P HD) and the low-pressure value (P ND) is less than a differential pressure threshold (SΔP), and d) after a defined duration (t), the start-up phase of the coolant compressor is terminated if the measured high-pressure value (P HD) and/or the measured low-pressure value (P ND) still satisfies one of the conditions to. - a coolant compressor, which can be adjusted by means of an actuation signal to control the compressor output, - a condenser or gas cooler, - an evaporator with an associated expansion valve, and - at least one pressure sensor (pT1, pT3) for measuring the coolant pressure on the high-pressure and/or low-pressure side of the coolant circuit, a) the actuation signal ST of the coolant compressor is provided so as to increase over time from a minimum value (STmin) in order to generate a start-up phase of the coolant compressor, b) a control signal maximum value (STmax) and a control signal threshold (STsw) are provided where STsw < STmax, c) the actuation signal is limited to the control signal maximum value (STmax) if the actuation signal reaches the control signal threshold (STsw) and the measured high-pressure and/or low-pressure value (P HD, P ND) satisfies one of the following conditions: the high-pressure value (P HD) is lower than the high-pressure threshold (S P_HD), the low-pressure value (P ND) is higher than the low-pressure threshold (S P_ND), and/or the difference (ΔP) between the high-pressure value (P HD) and the low-pressure value (P ND) is less than a differential pressure threshold (SΔP), and the high-pressure value (P HD) is lower than the high-pressure threshold (S P_HD), the low-pressure value (P ND) is higher than the low-pressure threshold (S P_ND), and/or the difference (ΔP) between the high-pressure value (P HD) and the low-pressure value (P ND) is less than a differential pressure threshold (SΔP), and d) after a defined duration (t), the start-up phase of the coolant compressor is terminated if the measured high-pressure value (P HD) and/or the measured low-pressure value (P ND) still satisfies one of the conditions to.