Vehicle HVAC system with cabin ventilation while parked

1. A heating, ventilation, and air-conditioning (HVAC) system configured to ventilate a cabin of a vehicle while the vehicle is parked, said system comprising:

a blower configured to urge air to flow from an inlet of the blower to an outlet of the blower, the outlet of the blower being upstream of a heater;

a fresh-air valve operable to provide a mixture of air drawn from an outside-air duct and a recirculated-air duct to the inlet, wherein the fresh-air valve is operable to a recirculate position where the outside-air duct is substantially blocked such that substantially all air provided to the inlet is from the recirculated-air duct; a bypass duct configured to couple the outlet to the same outside-air duct, from which the outside air is provided to the inlet of the blower; and a bypass valve located in the bypass duct and operable to a closed position and an open position, wherein the cabin is ventilated when the fresh-air valve is in the recirculate position, the bypass valve is in the open position, and the blower is operated, whereby air from the cabin is blown out of the outside-air duct, wherein the system has a setting, in which substantially all air blown out of the system is-blown out of the same outside-air duct, from which the outside air is provided to the inlet of the blower,

wherein the bypass duct defines an early bypass port, the system includes a separate temperature control valve located downstream of the outlet, the temperature control valve directing a portion of the air from the blower outlet through a heater and another portion of the air from the blower outlet around the heater, and the early bypass port is located to receive air from between the outlet and the temperature control valve.

2. The system in accordance with claim 1 , wherein the system includes an equalization vent configured to allow fresh air to replenish the cabin when the cabin is ventilated.

3. The system in accordance with claim 1 , wherein the system includes one or more cabin valves, each of the cabin valves operable to regulate airflow to the cabin through cabin vents that correspond with the cabin valves, and the all of the cabin valves are operated to a closed state when the cabin is ventilated.

4. The system in accordance with claim 1 , wherein the system includes one or more cabin valves, each of the cabin valves operable to regulate airflow to the cabin through cabin vents that correspond with the cabin valves, and one or more of the cabin valves are operated away from a closed state when the cabin is ventilated.

5. A heating, ventilation, and air-conditioning (HVAC) system configured to ventilate a cabin of a vehicle while the vehicle is parked, said system comprising:

a blower configured to urge air to flow from an inlet of the blower to an outlet of the blower, the outlet of the blower being upstream of a heater;

a fresh-air valve operable to provide a mixture of air drawn from an outside-air duct and a recirculated-air duct to the inlet, wherein the fresh-air valve is operable to a recirculate position where the outside-air duct is substantially blocked such that substantially all air provided to the inlet is from the recirculated-air duct; a bypass duct configured to couple the outlet to the same outside-air duct, from which the outside air is provided to the inlet of the blower; and a bypass valve located in the bypass duct and operable to a closed position and an open position, wherein the cabin is ventilated when the fresh-air valve is in the recirculate position, the bypass valve is in the open position, and the blower is operated, whereby air from the cabin is blown out of the outside-air duct, wherein the system has a setting, in which substantially all air blown out of the system is-blown out of the same outside-air duct, from which the outside air is provided to the inlet of the blower,

wherein the bypass duct defines a late bypass port, the system includes a separate temperature control valve located downstream of the outlet, the temperature control valve directing a portion of the air from the blower outlet through a heater and another portion of the air from the blower outlet around the heater, and the late bypass port is located to receive air from downstream of the temperature control valve.

6. The system in accordance with claim 5 , wherein the system includes an equalization vent configured to allow fresh air to replenish the cabin when the cabin is ventilated.

7. The system in accordance with claim 5 , wherein the system includes one or more cabin valves, each of the cabin valves operable to regulate airflow to the cabin through cabin vents that correspond with the cabin valves, and the all of the cabin valves are operated to a closed state when the cabin is ventilated.