Heater Core: Description and Operation

Heater Core Description

Temperature Valve and Heater Core

The air temperature from the heater duct and from the defroster nozzle is regulated by controlling the amounts of warm and cool air in the airflow coming from the heater module. The temperature door regulates the part of the total airflow through the heater module that is allowed to pass through the heater core. The temperature door is operated by the temperature control cable using a lever on the temperature door shaft.

If the temperature lever in the control assembly is in the extreme left end of its slot, or the full COLD position, the temperature door is positioned to stop all of the airflow through the heater core. This allows only unheated air to be sent to the heater duct and air defroster duct.

When the temperature lever is moved away from the full COLD (-) position, the temperature control cable opens the temperature door. This will allow an increasing amount of air to pass through the heater core. The temperature door reduces the amount of unheated air that is allowed to enter the mixture at the same time. The result is a responsive control of the temperature of the air that is discharged through the heater ducts and the air defroster duct.

When the temperature lever is at full HOT (+) position at the extreme right end of it slot, the temperature control cable holds the temperature door in a position that will divert all of the airflow through the heater core for maximum heating.

When the engine is running, hot coolant from the engine is sent through the heater core and returned to the cooling system.