Air Distribution System

PURPOSE
Within the heater module is a series of air valves called the temperature valve, vent valve, and the defroster valve. These air valves are hinged parts that act like doors to direct airflow through various sections of the heater module to provide the proper airflow for the selected operating mode. Each air valve is actuated by a control cable from the heater control assemble.

OPERATION
Temperature Valve and Heater Core
The temperature of the air coming from the air distribution duct is regulated by controlling the relative amounts of warm and cool air in the airflow coming from the heater module. The part of the total airflow through the heater module that is allowed to pass through the heater core is governed by the temperature valve. The temperature valve is operated by the temperature control cable, working through a lever on the temperature valve shaft. The valve defaults to full cold with no cable attached.

When the temperature rotary knob in the control assembly is in the full "COLD" position, the temperature valve is positioned to stop all of the airflow through the heater core so only unheated air is sent to the air distribution duct.

As the temperature rotary knob moves away from the full "COLD" position, the temperature control cable opens the temperature valve to allow an increasing amount of air to pass through the heater core. At the same time, the temperature valve reduces the amount of unheated air that is allowed to enter the mixture. This results in a very responsive control of the air temperature discharged through the heater ducts and defroster.

When the temperature rotary knob reaches the full "HOT" position, the temperature control cable holds the temperature valve in a position that diverts all of the airflow through the heater core for maximum heating.
Hot coolant from the engine is directed through the heater core and returned to the cooling system when the engine is running.