1) Check whether the engine coolant is sufficient.
2) Observe whether the engine coolant is normal. If it is normal, turn the temperature switch on the air conditioning control panel to the hottest position, and touch both ends of the heater switch on the water inlet pipe of the small water tank behind the engine. If the temperature difference between the two ends is large, there is something wrong with the heater switch, and the heater switch needs to be replaced.
3) If the warm air switch is normal, touch the temperature of the inlet and outlet pipes of the engine standby warm air small water tank by hand. If the outlet pipe temperature is low, the small water tank is blocked and needs maintenance.
4) If the fan speed is low or the fan does not rotate, check the fan, fan governor and fan circuit.
Please accept the above comments!