Why is the car heater not producing heat?

[LeMiles]

The reasons why the car heater is not producing heat are: 1. The blower malfunctions, causing issues with the air door flap or air door motor; 2. The coolant temperature sensor signal fails; 3. The heater core is clogged and requires disassembly, cleaning, or replacement; 4. The water pump loses rotation or is damaged, or the heater flow valve and coolant circulation valve are faulty; 5. The cooling system was not properly bled after coolant replacement. Solutions include: 1. Inspect the blower's operation at each speed setting to ensure sufficient rotation; 2. Install or replace the thermostat; 3. Bleed the system if there's a bleed port—if ineffective, manually check the two heater hoses for temperature differences and flush the heater core or heat exchanger with water or air if necessary; 4. Check if the filter is dirty or clogged, clean it, and replace it if needed; 5. Bleed the system promptly.