Automatic Modes

The automatic HVAC system will warm up/cool down and maintain the interior temperature of the vehicle by controlling the A/C compressor clutch, blower motor, air temperature, vacuum and recirculation actuators to achieve the desired temperature. For fully automatic operation, both the blower and mode switches must be in the AUTO position. Blower speeds will change automatically based on inputs to the HVAC control processor. The HVAC control module will always come back to the last settings after an ignition cycle or, if equipped, to the last settings of the driver by pressing the UNLOCK button on the remote keyless entry fob and placing the ignition in RUN. Only FRONT DEFROST and manual RECIRCULATION will have to be reset after each ignition cycle.

Moisture tends to accumulate in the HVAC module assembly after the engine has been shut off. The HVAC control processor will purge the HVAC module of stale air and moisture to prevent window fogging. The blower motor is delayed until the engine coolant temperature reaches 36°C (97°F) or the program number would result in cooling. If neither of these conditions exists within approximately 1-4 minutes (depending upon ambient temperatures), the HVAC control processor automatically resumes normal operation. The HVAC control processor will move to the floor mode and run the low blower to purge out the air and moisture. Purge mode can be bypassed if any manual modes are selected.

In cold temperatures, the automatic HVAC system will provide heat in the most efficient manner. On cold engine start-up, low blower speed will be selected and airflow will be directed on the windshield. This is done to prevent windshield fogging. The normal operation resumes after the engine coolant temperature reaches 36°C (97°F) or the program number would result in cooling. If neither of these conditions exists within approximately 1-4 minutes (depending upon ambient temperatures), the HVAC control processor automatically resumes normal operation. To warm the interior quickly, maximum heat mode is used where the blower is at maximum speed, floor mode, air temperature actuator is in full hot and ambient air is being drawn in. The vehicle operator can select the extreme warm setting of 32°C (90°F), but the system will not warm the vehicle any faster or regulate the blower speed. Once the desired temperature is reached, the blower motor, mode, recirculation and temperature will be adjusted automatically by the HVAC control processor.

In warm temperatures, the automatic HVAC system will provide A/C in the most efficient manner. On vehicle start up, the HVAC control module will monitor for conditions that indicate the possible presence of moisture in the HVAC module. To avoid blowing hot air and moisture out at the driver, the HVAC control module moves the mode door toward the floor and runs the medium speed blower for 4 seconds. This purge mode can be bypassed if any manual mode is chosen or if the blower was left on HI speed before turning off the vehicle. To cool the interior quickly, maximum cool mode is used where the blower is at maximum speed, air temperature actuator is in full cold and the recirculation actuator is drawing air from inside the vehicle. The vehicle operator can select the extreme cool setting of 16°C (60°F), but the system will not cool the vehicle any faster or regulate the blower speed. Once the desired temperature is reached, the blower motor, mode, recirculation and temperature will be adjusted automatically by the HVAC control module.