Why does the fan of BYD S6 spin when the hot air is turned on?

The engine temperature is too high. The BYD S6 fan will start when it is heated because the temperature in the engine compartment is very high, and it will start to cool down the engine compartment. BYD S6 is BYD's first SUV. S6 is positioned as a mid- to high-end independent SUV and was launched in September 2010.