Chevrolet Light Duty Truck 1973 Service Manual page 96

1A-70 HEATER A N D AIR C O N D IT IO N IN G
7. Evacuate, charge and check the system.
BLOWER MOTOR
Removal
1. Disconnect the battery ground cable and compres­
sor clutch connector.
2. Remove the Front Blower-Evaporator Cover as
previously described.
3. Disconnect the blower motor feed wire and ground
wires.
4. Remove the blower-evaporator cover brackets from
the assembly.
5. Remove the top half of the blower-evaporator case.
6. Remove blower motor mounting strap.
7. Remove blower assembly. Loosen the blower wheel
setscrews and remove the wheels from the motor
shaft.
Installation
1. Install the blower wheels on the motor so that the
lower blades curve toward the dash panel side of
the unit when the motor is placed in the case. Do
not tighten setscrews at this point.
2. Place the motor in the bracket with the electrical
connector side of the motor to the right side of the
bracket. Attach the mounting strap. Aligh blower
wheels so that they do not contact case. Tighten
setscrews.
3. Reverse removal Steps 1-5 for proper installation.
ELECTRICAL COMPONENTS
The front and rear blower switches, thermostatic switch,
front and rear resistors, blower and tie relays are
attached to the blower-evaporator assembly (fig. 80).
BLOWER SWITCH-
FLOOR SYSTEM
BLOWER RELAY-
THERMOSTATIC
FLOOR SYSTEM
S - ™ J fR LA Tv 0 '
w i t c h
SYSTEM SYSTEM
Fig. 80- Electrical Components (G Floor Mounted
System)
Replacement
1. Disconnect the battery ground cable and compres­
sor clutch connector.
2. Remove the blower-evaporator cover as described
previously.
3. Disconnect the electrical harness at the switch.
4. Remove the attaching screws and remove the
switch.
5. To install, reverse Steps 1-4 above. Check system
operation.
LOW REFRIGERANT CHARGE PROTECTION
SYSTEM
The low refrigerant charge protector system consists of a
superheat shutoff switch located in the rear head of the
compressor, connected in series by an electrical lead to a
thermal fuse.
During normal air conditioning system operating conditions,
current flows through the air conditioner thermostatic control
switch, and through the thermal fuse link to the clutch coil to
actuate the compressor clutch. Should a partial or total loss of
refrigerant in the system cause the superheat switch to sense
low system pressure and a high suction gas temperature, the
superheat switch contacts will close. When the contacts close,
current flows to energize the resistance type heater in the
thermal fuse, Figure 81. The resultant heat warms the fuse link
to its specific melt temperature, thus opening the circuit to the
compressor clutch coil. Compressor operation ceases and com-
RESISTOR-
OVERHEAD
SYSTEM
Fig. 81-Superheat Switch Electrical Schematic
LIGHT DUTY TRUCK SERVICE MANUAL