Purge Modes
Cold Air PurgeThe humid air which collects around the heater core inside the air distribution module could cause windshield fogging during a start in cool weather with a still warm engine. A purge routine is programmed into the H-A/C control to prevent this. With coolant temperature at least 16°C (60°F) and with the blower motor and the air distribution in the AUTO mode, the air valves move to guide the airflow away from the windshield. During the first five seconds, while the air valves are moving into position, the blower motor does not run. Then, during the next 30 seconds a low blower motor speed purges the moist air from the system. After that the system goes to the normal operating mode.
Hot Air Purge
Warm moist air can accumulate around the evaporator (from the previous A/C operation and/or from the heat soak from the sun) during a start in warm weather. The H-A/C control disables the blower motor for 5 seconds while the mode valves position to divert the air to the floor outlets to divert this undesirable air from the driver's face. The heater and air conditioning control sets the blower motor on low for 30 seconds to purge the air from the module before returning to the AUTO mode after positioning the mode valves.