GMC 1982 Light Duty Truck Service Manual page 26

Standard H e a te r................................................................................................. 1 A - 1
Auxiliary H e a t e r .............................................................................................. 1A-15
Specifications..................................................................................................... 1A-20
General Description............................................................ .1 A - 1
System C o m po ne n ts ............................. ........................... .1 A - 1
System C o n tr o ls .................................................... ........... .1 A - 1
Diagnosis................................................................................ .1A-4
On Vehicle Service
Blower M otor..................................................................... .1A-8
Heater Distributor and Core Assembly...................... .1A-8
Heating components are attached to the dash panel on
the right side of the vehicle. The blower and air inlet
assembly and water hoses are located on the forward side of
the dash panel while the heater core and distributor duct are
on the passenger side.
The heater system is an air mix type system in which
outside air is heated and then mixed in varying amounts
with cooler outside air to attain the desired air temperature.
The system consists basically of three parts: (1) the blower
and air inlet assembly, (2) the heater distributor assembly
and (3) the heater control assembly.
HEATER AIR FLOW SCHEM ATIC
C-K Series heater airflow is shown in Fig. 1 A - 1.
BLOWER A N D AIR INLET ASSEMBLY
The blower and air inlet assembly draws outside air
through the outside air inlet grille located forward of the
windshield reveal molding and channels the air into the
heater distributor assembly. The operation of the blower
motor is controlled by the FAN switch on the heater control.
The motor is connected in series with the FAN 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.
HEATER DISTRIBUTOR ASSEMBLY
The heater distributor assembly houses the heater core
and the doors necessary to control mixing and channeling of
SECTION 1A
HEATER
CONTENTS
STANDARD HEATER
INDEX
Heater H o se s..................................................................... 1A-9
Center Distributor Duct ................................................. 1A-9
Defroster D u c t................................................................... 1A-9
Control A ssem bly............................................................. 1A-9
Control C ables................................................................. 1A-11
Blower Switch.................................................................. 1A-11
Resistor U n i t ................................................................... 1A-11
GENERAL DESCRIPTION
the air. Since the unit has no water valve, water circulation
keeps the core hot at all times. That portion of the air
passing through the core receives maximum heat from the
core. Air entering the distributor assembly is channeled as
follows:
C-K Models
purge door opening, on the right end of the distributor
assembly, by the purge door. If the purge door is closed, then
air is directed through and/or around the heater core by the
temperature door. Air is then directed into the passenger
compartment through the heater (floor) outlets and/or the
defroster (dash) outlets by the defroster door. The
temperature of the outlet air is dependent on the ratio of
heated to unheated air (controlled by the temperature door).
G Models
assembly. The air door can be adjusted to vary airflow. If air
is allowed to enter the distributor assembly, it is then
directed through and/or around the heater core by the
tem p e ra tu re door. Air is directed into the passenger
compartment through the heater (floor) an d /o r defroster
(dash) outlets by the defroster door. The temperature of the
outlet air is dependent of the ratio of heated to unheated air
(controlled by the temperature door).
CONTROLS
Fig. 1A-2 and 1A-3.
Air entering the distributor can be directed out the
Air flow is controlled by doors in the distributor
Heater controls for C-K and G Models are shown in
HEATER 1 A-1