The reasons why the warm air in old Pu Sang is not hot are: 1, the thermostat is always on or the thermostat is turned on too early, which makes the refrigeration system cycle too early and the outside temperature is very low; 2. The water pump impeller is damaged or lost, so that the flow through the warm air small water tank is not enough, and the heat does not come up; 3. There is air resistance in the engine cooling system, which leads to poor circulation of the cooling system; 4. The filter screen is dirty and blocked, which leads to insufficient air volume or poor distribution of hot and cold air, so that the heat of the warm air small water tank cannot be radiated. Pu Sang is a Santana model of Volkswagen series, which is a brand car produced by Volkswagen in California. Its models include: Santana 87, Santana 2000, Santana 3000, Santana vista Zhijun, brand-new Santana and so on.