What Are the Reasons for the Heater Not Blowing Hot Air When the Engine Temperature Rises?

[SanSteven]

The reasons for the heater not blowing hot air when the engine temperature rises are: 1. The air filter is dirty or clogged, significantly reducing the airflow and affecting the heating efficiency; 2. The thermostat is stuck open or opens too early, causing the cooling system to enter the major circulation prematurely. If the outside temperature is very low, the cold air while driving will quickly cool the antifreeze, preventing the engine from reaching the optimal temperature and the heater from blowing hot air; 3. The water pump impeller is damaged or slipping, resulting in insufficient flow through the heater core, which affects heat transfer; 4. The heater core is clogged, preventing the heat from dissipating properly; 5. The control cable for the heater's hot/cold air flap is detached, the heater blower is damaged, the flap is dislodged, or the heater valve is faulty.