A monitoring system is configured to monitor a property. The system includes a sensor that is configured to generate sensor data that reflects an attribute of the property. The system further includes an HVAC system that is configured to generate and provide conditioned air to the property and that is configured to generate HVAC system data that reflects an attribute of the HVAC system. The system includes a monitor control unit that is configured to determine that the HVAC system is likely malfunctioning. The control unit is configured to receive the sensor data. The control unit is configured to determine that the HVAC system is likely operating correctly. The control unit is configured to determine a cause of the HVAC system transitioning from likely malfunctioning to likely operating correctly. The control unit is configured to update a model that is configured to identify causes of HVAC system malfunctions.