Heater Core

The heater core looks like a little radiator. It is normally mounted between the engine compartment and the passenger compartment on the firewall. Coolant from a warm engine flows through the heater core and radiates thermal heat energy. When you turn on the heater blower the heat is transferred into the passenger cabin of the vehicle through the heating/air conditioning ducts. If you notice a sweet odor in your car when you turn on your heat you may have a heater core leak. If it is leaking, it drips in the heater ducts and sometimes on the floor inside the car. When the blower is turned on, the odor circulates inside the passenger compartment. Check to see if your coolant level is low if you believe you have a leak.