Chevrolet 1977 light duty truck Service Manual page 32

Tem perature Lever
This lever controls the positioning o f the TEM PER -
ATURF. door in the heater distributor assembly. All
incoming "outside" air is directed around the heater core
in the C O L D position or through the core in the HOT
position. The desired outlet tem perature is obtained by
blending heated an d unheated air according to the
setting o f the tem perature lever.
H eater-D ef Lever
T he H E A T E R -D E F lever controls positioning o f the
A IR and D E F R O S T E R doors in the heater distributor
assembly. In the O F F position, no air is allowed to enter
the system. Moving the lever to the right (toward
HEATER) opens the air door with the AIR door being
fully open at the H EATER position. Incoming air is
directed to the heater outlets (with slight air bleed to the
defroster outlets). Moving the lever between HEATER
and DKF, directs increasing amounts of air to the
defroster outlets until all air is directed to the defroster
outlets in the D EF position.
Fan Control
The blower fan lever is located on the left h an d side
o f the control assembly. W hen the lever is fully down,
the blower motor is inoperative. M oving the lever
upward actuates the three speed blower motor (LOW-
MED-HI).