An HVAC system for work vehicle having an operator compartment for an operator is disclosed. The HVAC system includes a pressurizer blower and an air-conditioning system coupled to an electronic circuit. The electronic circuit is configured to reduce the output of the pressurizer blower when the operator selects a high output from the air-conditioning system. The HVAC system is also configured to provide defog operation in both a manual mode and an automatic mode of operation. The HVAC system is configured to reset the defog operation when the vehicle ignition is turned off or turned back on. The HVAC system is also configured not to reset the defog operation when the operator switches rapidly between the automatic mode and the manual mode of operation.