Where is the preheating switch of Longgong loader?

Located between the engine main water tank and the warm air water tank. According to the relevant data of Longgong loader, the warm air valve of Longgong 855n loader is located between the main water tank and the warm air tank of the engine. The warm air valve is the warm air switch of the automobile heater. The working principle of the heater is that the radiator in the heater is connected with the circulating water of the engine through a pipeline, 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.