Why is there hot air when the car's air conditioning is not turned on?

[McConnor]

The reasons why there is hot air when the car's air conditioning is not turned on are: 1. The internal circulation mode is not activated. When the air conditioning is off, to ensure air circulation inside the car, it automatically switches to external circulation mode. The outside air passes through the engine compartment and becomes heated; 2. The temperature switch is not set to the coldest state. In this case, the air mixing damper remains open, allowing heat from the engine coolant to enter the car through the damper. It is normal for hot air to be present when the car's air conditioning is off, and there is no need to panic. Moreover, this is the direct reason why using the heater in winter is more fuel-efficient than using the air conditioner in summer. External circulation uses a fan to draw outside air into the car. When driving in urban areas with heavy traffic, the car may fill with exhaust fumes due to external circulation. Internal circulation blocks the flow of outside air into the car, preventing harmful external gases from entering and also helping to maintain warmth.