Temperature Valve and Heater Core

The temperature of the air coming from the heater duct and defroster nozzle is regulated by controlling the relative amounts of warm and cool air coming from the heater module. The amount of the total airflow that is allowed to pass through the heater core is governed by the temperature valve.

When the temperature knob is in the BLUE (Cold) end of its travel, the temperature valve is positioned to stop all of the airflow through the heater core so only unheated air is sent to the heater duct and defroster nozzle.

When the temperature knob reaches the full RED (Hot) end of its travel, the temperature valve 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.