Abstract: A control method for a motor vehicle HVAC system categorizes potentially conflicting override commands for at least one control parameter in order to assign a priority of control. Override commands are categorized as being related to occupant safety, vehicle safety or occupant comfort. Highest priority is assigned to override commands categorized as being related to occupant safety, second-highest priority is assigned to override commands categorized as being related to vehicle safety, and third-highest priority is assigned to override commands categorized as being related to occupant comfort. An HVAC controller carrying out the control method then regulates the control parameter in accordance with the override command that has been assigned the highest priority.

Abstract: An air cycle automotive air conditioning system for providing conditioned air to an automotive passenger compartment (20) includes an air compressor (10) tandemed to an expander (12). The expander (12) is efficiently run so as to expand air to a very low temperature, sending recovered work back to the compressor (10). The very cold expander air is then mixed with warmer air from other sources, providing a proper volume flow and temperature of air to the passenger compartment (24).