METHOD FOR DEFROSTING AN EXTERNAL HEAT EXCHANGER, WHICH IS OPERATED AS AN AIR HEAT PUMP, OF A COOLING SYSTEM FOR A MOTOR VEHICLE, COOLING SYSTEM, AND MOTOR VEHICLE HAVING SUCH A COOLING SYSTEM

A method for defrosting an external heat exchanger, operated as an air heat pump evaporator, of a cooling system for a motor vehicle. The cooling system includes a refrigerant compressor connected to a primary and secondary section; an external heat exchanger; an evaporator; a heating register; a primary section valve which is closed in the air heat pump operation; and a secondary section valve which is open in the air heat pump operation. The method includes closing of the secondary section valve; opening of the primary section valve, so that refrigerant flows directly from the refrigerant compressor to the external heat exchanger; and setting an inlet-side pressure level of the refrigerant on the external heat exchanger to a target pressure which corresponds to a condensation temperature (Tkond) of the refrigerant in the range: 2° C. ≤ Tkond ≤ 20° C., in particular 4° C. ≤ Tkond ≤ 10° C.