An air-conditioning plant comprises a cooling circuit which in turn comprises an evaporator (6) for the coolant flowing in from a pressure-reducer(15), a compressor (7) for the coolant flowing in from the evaporator and a device (9) to change the supply capacity of the compressor by changing the control value of the inlet pressure of the compressor corresponding to a control flow value passed to it; The plant also has a device (26) to establish the high pressure-side pressure of the coolant circuit, a device (102) to establish the low pressure-side pressure of the coolant circuit and a device 9103) to calculate the torque needed to drive the compressor on the basis of the established high pressure- side and low pressure-side pressures. Independent claim is included for a method for adjusting an externally variable compressor of a vehicle air conditioner.
