Automatic Mode

WARNING: This page is about a different car, the 2002 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.

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, mode and recirculation actuators to achieve the selected temperature. Both the blower and mode switches must be in the auto position for fully automatic operation. Blower speeds will change automatically based on inputs to the Instrument Panel Module (IPM). The IPM 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.

When the engine is first started, the mode actuator will move to the floor mode and run the blower at low speed for 10 seconds to purge accumulated moisture in the HVAC assembly to prevent window fogging. Purge mode can be by-passed if any manual modes are selected during the 10 second purge.

In cold temperatures, the HVAC system will provide heat in the most efficient manner. When starting the engine in cold weather, the blower operates for 3 minutes and the IPM directs mode outlets to the windshield. In order to prevent windshield fogging, as coolant temperature increases, blower speed is increased. The purge can be by-passed if any manual modes are selected. To warm the interior quickly, maximum heat mode is used when the blower is set at maximum speed, air temperature door actuator is in floor mode, temperature is full hot and ambient air is being drawn in. Once the desired temperature is reached, temperature, mode and blower motor will be adjusted automatically by the IPM.

In warm temperatures, the Automatic HVAC system will provide A/C in the most efficient manner. On vehicle start up, the IPM moves the mode door toward the floor and runs the blower for 3 seconds to avoid blowing hot, moist air on the driver. The IPM will monitor for conditions that indicate the possible presence of moisture in the HVAC module. This purge mode can be by-passed if any manual modes are selected. To cool the interior quickly, maximum cool mode is used when the blower is at maximum speed, air temperature actuator door is in full cold and the recirculation actuator is drawing air from inside the vehicle. The vehicle operator can select the extreme cool setting, but the system will not cool the vehicle any faster. Once the desired temperature is reached, temperature, mode and blower motor will be adjusted automatically by the IPM.