First try: If the air conditioner can reach the set temperature after half an hour of opening, and if the running lamp is on and off for a while, otherwise, there will be a lack of fluorine.
Second measurement: Use thermometer to measure the temperature difference between the inlet and outlet of indoor machine. The difference is more than 10 degrees, even if it is normal. If the temperature difference is too small, it will be fluorine-deficient.
Third look: 15 minutes after start-up, open the interior panel; should see that the evaporator is evenly covered with condensate, if there is no or frost, ice is abnormal. Either fluoride deficiency or compressor is not working.
Four Touches: 15 minutes after starting, there should be a great temperature difference between the two valves of the external machine. The frosting of the thin tube indicates the lack of fluorine, while the frosting of the thick tube means the system is not flowing smoothly.