A Typical Cold Weather Example

The vehicle has been parked overnight in cold weather (below 0°C/32°F) and the driver has set the automatic temperature setting to 23°C (73°F). The system will automatically adjust the temperature output to maximum heating. The fan will start at low speed to avoid blowing cold air into the vehicle. The length of delay depends on the amount of time since the engine was last started, the outside temperature and the engine coolant temperature. As the coolant warms up, the fan speed will gradually increase. Air will flow to the floor with some air to the windshield to prevent fogging under most normal conditions.

As the interior of the vehicle warms up to the set temperature, the fan speed will decrease and the temperature output may become cooler. If the interior temperature continues to warm up due to heating from the sun or outside temperature increases, the system may switch to other air delivery modes (typically DEFOG or BI-LEVEL).