No hot air enters the car interior
Faulty thermostat. Replace.
Faulty heater control drive. Check and make necessary repairs.
The patency of the heating hose is broken. Remove the blockage or replace the hose.
The patency of the heater heat exchanger is broken. Clean or replace heat exchanger.
Note. Make sure the engine is warmed up to normal operating temperature. If you are not sure, check the thermostat for proper operation.
After the engine has warmed up, both heating hoses should feel warm/hot to the touch (see accompanying illustration). In case of violation of the patency of the heat exchanger, one hose will be noticeably colder than the second.
Cooled air does not enter the car interior
The air conditioning compressor drive belt is slipping or broken. Replace belt and/or adjust belt tension (see the relevant subsection in Chapter Settings and ongoing maintenance).
The coolant level has dropped. Check system for leaks (see accompanying illustration), add if necessary.
A/C compressor not working properly. With the ignition on, turn on the air conditioning system and make sure the compressor clutch is engaged, you should hear a distinct click. Otherwise, before proceeding with the removal of the compressor for repair in a specialized workshop, check the correctness of the power supply to it.
Warm air from the heating system is mixed with cooled air. Check that the heating system is working properly. Adjust control cables. Replace defective components.
Note. The diagnostic procedures listed above are only basic checks. If there is strong suspicion of a malfunction of the air conditioning system, it is recommended to drive the car to a specialized workshop for a series of professional checks and carry out the necessary repairs.
Do not be alarmed if you find traces of water under the car when it is parked in hot weather. Usually this is just condensate formed during the operation of the air conditioning system.