The purpose of the heater core is to:

• A. Cool the engine coolant
• B. Power the air conditioner
• C. Provide heat for the passenger compartment
• D. Purify coolant

Answer: (C)

The heater core’s job is to provide heat for the passenger compartment. It acts like a tiny radiator inside the car’s heating system: hot engine coolant flows through the heater core, and a blower pushes air across its warm tubes and fins. The air picks up that heat and is directed into the cabin, warming the interior when you set the heat.

This isn’t about cooling the coolant—the radiator handles that by removing heat from the coolant before it returns to the engine. It isn’t part of the air conditioning system, which uses a refrigerant cycle to cool air. And it doesn’t purify coolant; that’s not a function of the heater core.