Heater cores are compact heat exchangers responsible for warming cabin air via engine coolant. Located within the vehicle’s HVAC system, typically inside the dashboard, they receive hot engine coolant from the cylinder head. Fin and tube construction maximizes heat transfer to airflow generated by the blower motor. Core materials commonly utilize aluminum or copper, with multi-path designs increasing thermal efficiency. Failure modes include corrosion, leaks, and blockage, often requiring complete unit replacement.