The fan in your car's heating system is responsible for circulating the warm air generated by the heater core throughout the cabin. When the fan is turned on, it draws in cool air from the outside and passes it over the heater core. The hot air from the heater core then rises and is distributed throughout the cabin.
If you leave the fan off, the hot air from the heater core will still be generated, but it will not be circulated as effectively. This means that it will take longer for the warm air to reach the cabin and for the car to feel warm. Additionally, the heat generated by the heater core may cause the engine to overheat if it is not adequately circulated.
Therefore, it is generally recommended to turn on the fan when using the heater in your car to ensure quick and efficient heating of the cabin.
