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 (ST) 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 (ST) is limited to the control signal maximum value (STmax) if the actuation signal (ST) 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: (I) the high-pressure value (P HD ) is lower than the high-pressure threshold (S P_HD ), (II) the low-pressure value (P ND ) is higher than the low-pressure threshold (S P_ND ), and/or (III) 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 (I) to (III). - a coolant compressor , which can be adjusted by means of an actuation signal (ST) 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 (ST) is limited to the control signal maximum value (STmax) if the actuation signal (ST) 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: (I) the high-pressure value (P HD ) is lower than the high-pressure threshold (S P_HD ), (II) the low-pressure value (P ND ) is higher than the low-pressure threshold (S P_ND ), and/or (III) 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 (I) the high-pressure value (P HD ) is lower than the high-pressure threshold (S P_HD ), (II) the low-pressure value (P ND ) is higher than the low-pressure threshold (S P_ND ), and/or (III) 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 (I) to (III). <EOS>