- the thermostat does not close, as a result of which the liquid does not warm up enough and heats up the heater radiator poorly - replace the thermostat (see subsection 4.3);
- the heater hose is clogged, which prevents the flow of fluid through the radiator - disconnect the hoses and flush the radiator with a jet of water from the hose;
- if water does not flow through the heater core, the heater core is clogged and must be replaced.
2. If no air comes out of the air duct outlets, proceed as follows:
- turn the ignition key to the ON position and turn on the fan (the noise of a running electric motor should be heard);
- if the hum of the motor is not audible, or if the check shows that the switch and resistor block are OK, then the cause may be a malfunction of the motor.
3. If the mat is damp or coolant vapor is leaking through the vents, there is a leak in the heater core. Replace radiator.
4. Check the water separator drain hose for cleanliness.