Heater Core
WARNING: This page is about a different car, the 2003 Ford Pickup, 2003 Ford F550 Super Duty, 2003 Ford F450 Super Duty, and 2003 Ford Excursion. However, it is still accessible from the selected car via links, so may be relevant.
The heater core consists of fins and tubes arranged to extract heat from the engine coolant and transfer it to air passing through the heater core from the blower motor.