Method of operating a heat pump laundry dryer and heat pump laundry dryer or heat pump washing machine having drying function

The invention relates to a method of operating a heat pump laundry dryer or a heat pump washing machine having drying function and to such a laundry dryer or washing machine, wherein the laundry dryer or washing machine comprises: a control unit (30) controlling the operation of the laundry dryer or washing machine, a laundry treatment chamber (18) for treating laundry using process air, a process air circuit for circulating the process air, a heat pump system (4) having a refrigerant loop, in which the refrigerant fluid is circulated through a first and a second heat exchanger (10, 12), a compressor (14) for circulating the refrigerant fluid through the refrigerant loop, and a cooling fan unit (24) for cooling the compressor (14), and wherein the method comprises: modifying or changing an operation parameter set of the cooling fan unit (24) in dependency of at least one of the following input variables: a user selectable input variable, a working parameter of the laundry drum, a working parameter of a process air fan, a working parameter of an electric driving motor, a working parameter of the compressor, a drying progress status parameter or a status parameter of the laundry to be dried, and an environment parameter of the treatment apparatus environment.