Description Adn Operaton (page 3 of 6)

 
The air inlet duct is installed behind the instrument panel, on the front passenger side, and connected between the 
plenum chamber below the windshield and the heater. 
 
The plenum chamber is formed by the upper and lower cowl and a plenum molding. Grilles in the plenum molding allow 
fresh air into the plenum chamber. From the plenum chamber, the air passes through a water separator and into the fresh 
air inlet of the air inlet duct. 
 
The air inlet duct incorporates a grille to provide the inlet for recirculated air from the vehicle interior. The air inlet duct also 
accommodates: 
 

The cabin air filter. For additional information, refer to   

Air Distribution and Filtering

 (412-01 Air Distribution and 

Filtering) 
The blower.  
The blower control module.  

The outlet from the air inlet duct forms the rear wall of the heater, enclosing the evaporator and incorporating the two 
evaporator drain outlets. Drain tubes connect the evaporator drain outlets to the transmission tunnel, to direct the water 
that condenses on the evaporator overboard. 
 
A recirculation door is installed between the fresh and recirculated air inlets, to control the source of incoming air. A lever 
on the recirculation door is driven by the recirculation door motor. Operation of the recirculation door motor is 
automatically controlled by the Air Temperature Control Module (ATCM) and manually controlled by a switch on the 
ATCM control panel. For additional information, refer to   

Control Components

 (412-04 Control Components) 

 
 
Fresh or recirculated air enters the air inlet duct and passes through the cabin air filter to the hub of the blower. From the 
blower, the air flows to the outlet of the air inlet and into the heater. The blower, and ram effect from the forward motion of 
the vehicle, forces the air through the air inlet duct. 
 

Air Flow Through Air Inlet Duct 

6

 -

Air inlet duct

7

 -

Recirculation air inlet

Item  Part Number 

Description 

1

 -

Upper cowl