2. We start the engine.
3. Move the lower lever of the heater control unit to the leftmost position (blue sector).
4. Using the heater fan control knob, turn on the three speeds of the electric fan in turn. By the intensity of the air flow from the ventilation grilles, we check the operation of the electric fan and the change in its speed of rotation when changing modes (1 - minimum speed; 2 - average speed; 3 - maximum speed). If the electric fan does not work in all modes, then we check the additional resistor (see "Additional resistor - removal, check and installation") and switch. If the electric fan does not turn on at all, then check the power supply circuit of the electric fan (see "Electrical equipment - checking the technical condition").
5. Turn on the maximum speed of the electric fan.
6. By moving the left upper lever of the heater control unit, we monitor the change in the direction of the air flow from the central ventilation grilles to the area of the legs of the driver and passengers. If there is no change in flow distribution, then the damper actuator is most likely defective.
7. By moving the upper right lever of the control unit, we check the change in the intensity of blowing the windshield and front door windows. If there is no change in the intensity of blowing the windows, then the drive of the air duct dampers is most likely faulty.
8. Warming up the engine to operating temperature, we translate the lower lever of the heater control unit into the red sector.
9. We are convinced that the temperature of the air leaving the ventilation grilles begins to rise. If the temperature does not rise, then the central damper actuator or heater valve may be faulty, or the heater radiator is clogged.
10. After the temperature of the air leaving the heater reaches its maximum, move the lever to the blue sector - the temperature of the air supplied should quickly drop. If the temperature does not drop, either the heater valve or the central damper drive is faulty.
11. Under the instrument panel on the passenger side, we visually check that there is no leakage of coolant from the heater radiator tap. Replace defective faucet (see below, "Heater tap - removal and installation").