Chevrolet 1977 light duty truck Service Manual page 31

BLOWER AN D AIR IN LET ASSEMBLY
T he blower and air inlet assembly draws outside air
through the outside air inlet grille located forward o f the
windshield reveal m olding and channels the air into the
heater distributor assembly. The operation of the blower
motor is controlled by the FA N switch on the heater
control. The motor is connected in series with the FA N
switch and also the blower resistor assembly. Located in
the fuse block, in series between the blower motor and
the battery, is a 25 amp. fuse C-K models - a 20 am p
fuse on G models.
HEA TER D IS T R IB U T O R ASSEMBLY
T he heater distributor assembly houses the heater
core an d the doors necessary to control mixing and
c hanneling o f the air. Since the unit has no w ater valve,
water circulation keeps the core hot at all times. That
portion of the air passing through the core receives
m ax im um heat from the
distributor assembly is channeled as follows:
C-K Models
A ir entering the distributor can be directed out the
purge door opening, on the right end o f the distributor
assembly, by the purge door. If the purge door is closed,
then air is directed through a n d / o r around the heater
core by the tem perature door. Air is then directed into
the passenger com partm en t through the heater (floor)
outlets a n d / o r the defroster (dash)
defroster door. The tem perature o f the outlet air is
de p e n d e n t on the ratio o f heated to unheated air
(controlled by the tem perature door).
G Models
A ir flow is controlled
distributor assembly. The air door can be adjusted to
vary airflow. If air is allowed to enter the distributor
assembly, it is then directed through a n d / o r around the
heater core by the tem perature door. Air is directed into
the passenger co m p artm en t through the heater (floor)
a n d / o r defroster (dash) outlets by the defroster door.
The tem peratu re o f the outlet air is dependent o f the
Fig. lA -3~ H eater C ontrol -C-K Models
core. Air entering the
outlets by the
by three doors in the
radio o f heated to unheated air (controlled by the
temperature door).
CO NTRO LS
C-K Models (Fig. 1A-3)
These controls are mounted in the center o f the
dash, above the radio assembly. The control incorporates
two levers which m ake use o f bowden cables to control
positioning o f the purge, tem perature and defroster
doors.
Tem perature Lever
This lever control the positioning o f the T E M P E R A ­
T U R E door in the heater distributor assembly. All
incoming "outside" air is directed around the heater core
in the CO LD position or through the core in the HO T
position. The desired outlet tem perature is obtained by
blending the heated and unheated air according to the
setting o f the tem perature lever.
Heater-Def Lever
The H E A T E R -D E F lever controls the position of
the D E FR O ST E R door and the P U R G E door. In the
O F F position, the blower is " o n " and incoming air is
directed up under the dash through the purge door
opening. As the lever is moved to the right o f the O F F
position, the door closes, directing airflow on into the
distributor assembly. With the lever at HEATER, the
D E FR O STE R door directs almost all airflow to the
heater (floor) outlets - a small am ount of air is directed
to the defroster (dash) outlets. In the D E F position, most
airflow is diverted to the defroster outlets. Moving the
lever part way, as desired, will split airflow between the
floor and defroster outlets.
Fan Control
The blower fan lever is located at the left hand side
o f the control assembly. The blower motor will operate
as soon as the ignition switch is turned to the R U N
position. The control has three' positions only; LO, MED,
HI. There is no O F F position.
G Models (Fig. 1A-4)
The controls are located in the instrum ent panel,
just to the right o f the instrument cluster. In opeation,
two levers control all heating operations.
Fig. 1A-4- Heater C ontrol-G Models