What the owner reported
The owner described a very specific pattern: the aircon was cold while the car was moving, but blew warm air whenever the car was stationary or idling.
This is a recognisable pattern. When a car is moving, air passes through the condenser at the front of the car naturally. When the car stops, the condenser relies entirely on the fan to keep drawing air through it. If the fan motor has failed, the condenser cannot release its heat at idle, and the refrigerant circuit backs up. Cooling stops.