Warm up the engine to operating temperature.
Set the air temperature control to the lowest temperature and the heater fan control knob to the highest speed. Open the car doors.
After the air conditioning system has provided the required temperature, check the temperature of the two pipelines on the bulkhead of the engine compartment connected to the evaporator.
The thinner piping connecting the evaporator to the condenser should be a well, and the thicker piping connecting the evaporator to the compressor should be even colder - 2-5°C. If the pipe connecting the evaporator to the compressor is significantly warmer than the pipe connecting the evaporator to the condenser, the system needs to be recharged. Insert the thermometer into the central ventilation grilles of the instrument panel when the air conditioning system is operating in the maximum cooling mode - the temperature shown by the thermometer should be 15-20°C lower than the air temperature in the car. If the temperature difference is much smaller, the system probably needs to be recharged.
If warm air is blown from the ventilation grilles, check the operation of the A/C compressor clutch. Have an assistant turn on the air conditioning system while you look at the front of the compressor. The clutch should make an audible click when engaged and the clutch hub should begin to rotate.
If the clutch does not work, check the fuses located in the instrument panel.
If the fuses are OK, check the circuit diagrams for compressor clutch and pressure sensor circuits.
If the compressor clutch and pressure sensor circuits are OK, the clutch is probably out of order.
If the compressor clutch, relays and their electrical circuits are OK, the system may need to be recharged with refrigerant. All further checks and repairs of the air conditioning system must be carried out at a service station