The warm air water valve is the warm air switch of the automobile heater. The working principle of the automobile heater is that the radiator in the heater is connected with the circulating water of the engine through the inlet and outlet water pipes, and the water valve is a switch. The water valve is opened, the waterway is connected, the circulating water of the engine enters the radiator, and the fan blows heat into the cab. On the contrary, the water valve is closed and the warm air doesn't work.