A condensation dryer is provided which has a heat pump in which a coolant circulates; a compressor; a temperature sensor to measure a temperature of the coolant; and a controller. The controller has a first comparator to compare the temperature of the coolant with an upper limiting temperature of the coolant; a switch to switch the compressor off if the temperature of the coolant is greater than or equal to the upper limiting temperature and to switch the compressor on after each compressor disconnection. A counter ascertains the number of occurrences at which the compressor is switched off. The counter is incremented by 1 each time the compressor is switched off. A second comparator compares the number of occurrences with a prespecified limiting number and evaluates the difference between the number of occurrences and the prespecified limiting number with respect to the presence of an impermissible operating state.