Lifan 720, cold and warm air is not easy to adjust. What's wrong with no hot air?

Lifan 720, the cold and warm air is not well adjusted, and there is no abnormal working temperature of the hot air engine. According to relevant data, the engine working temperature is low and the thermostat is not closed properly. Replace thermostat. The working temperature of the engine is normal, and the warm air pipe in the engine room is hot and cold, that is, the inside of the warm air box is blocked. It is recommended to clean it, remove the inlet and outlet pipes of the warm air and blow it out with a water gun or air pump. There is nothing wrong with the heating water pipe, that is, the servo motor of the cold and hot fan in the air conditioning bellows is not in place or the fan is stuck. Just check and adjust.