A method of operating a drying apparatus comprising a drum for receiving laundry items; a heat pump (4, 6, 8, 9) having an evaporator as a first heat exchanger, a condenser as a second heat exchanger, which are arranged in a process air duct at a distance one behind the other with respect to the flow direction thereof, a compressor and an expansion valve; a blower arranged in the process air duct, and a cleaning device for cleaning the first heat exchanger with an aqueous cleaning liquid, the method comprising the following steps in a drying phase in which the drum is at least temporarily rotated and the blower is switched on: (a) determining whether a predetermined minimum amount M min of the aqueous cleaning liquid is present in the cleaning device; when the minimum quantity M min of aqueous cleaning liquid is present in the cleaning device, switching off the compressor; when the minimum quantity M min of aqueous cleaning liquid is not present in the cleaning device, the following steps (c),, and (d) are skipped; (c) activating the cleaning device so that aqueous cleaning liquid is conveyed into the first heat exchanger, wherein during the conveyance of the aqueous cleaning liquid in the event that a moisture content H of the laundry items is above a predetermined moisture content H AT, the blower is operated at a power P 1 sufficient to convey at least part of the aqueous cleaning liquid from the first heat exchanger into the second heat exchanger; and in the event that a moisture content H of the laundry items is below a predetermined moisture content H CD, where H AT > H CD, operating the blower at a power P 2 < P 1 insufficient to convey at least a portion of the aqueous cleaning liquid from the first heat exchanger to the second heat exchanger, and interrupting rotation of the drum; (d) pumping condensate, preferably from a condensate pan in a bottom group, by means of a pump into the cleaning device until at least the minimum quantity M min of aqueous cleaning liquid is again present in the cleaning device, wherein in case the rotation of the drum is resumed before the pumping after de-activation of the cleaning device; (e) repeating steps (c) and (d) at least once; and then (f) in case, restarting the compressor; and (g) in case, rinsing the first heat exchanger when the temperature inside the drum reaches a pre-defined limit T lim. (a) determining whether a predetermined minimum amount M min of the aqueous cleaning liquid is present in the cleaning device; when the minimum quantity M min of aqueous cleaning liquid is present in the cleaning device, switching off the compressor; when the minimum quantity M min of aqueous cleaning liquid is not present in the cleaning device, the following steps (c),, and (d) are skipped; (c) activating the cleaning device so that aqueous cleaning liquid is conveyed into the first heat exchanger, wherein during the conveyance of the aqueous cleaning liquid in the event that a moisture content H of the laundry items is above a predetermined moisture content H AT, the blower is operated at a power P 1 sufficient to convey at least part of the aqueous cleaning liquid from the first heat exchanger into the second heat exchanger; and in the event that a moisture content H of the laundry items is below a predetermined moisture content H CD, where H AT > H CD, operating the blower at a power P 2 < P 1 insufficient to convey at least a portion of the aqueous cleaning liquid from the first heat exchanger to the second heat exchanger, and interrupting rotation of the drum; (d) pumping condensate, preferably from a condensate pan in a bottom group, by means of a pump into the cleaning device until at least the minimum quantity M min of aqueous cleaning liquid is again present in the cleaning device, wherein in case the rotation of the drum is resumed before the pumping after de-activation of the cleaning device; (e) repeating steps (c) and (d) at least once; and then (f) in case, restarting the compressor; and (g) in case, rinsing the first heat exchanger when the temperature inside the drum reaches a pre-defined limit T lim.