GMC 1976 ZEO 6083 Maintenance Manual page 67

1- 50 AIR CONDITIONING SYSTEM
That the leakage of refrigerant can be so silent
that the complete charge may be lost without warn-
ing.
That refrigerant gas is heavier than air and will
rapidly drop to the floor as it
flows
from a point of
leakage.
That the pressure in the system may momentarily
become as high as 480 lbs. per square inch.
That the total refrigerant charge circulates
through the entire system at least once each minute .
That the compressor is continually giving up
some lubricating oil to the circulating refrigerant and
depends upon oil in the returning refrigerant for con
tinuous replenishment. Any stoppage or major loss
of refrigerant will therefore damage the compressor .
That the extreme internal dryness of a properly
processed system is a truly desert condition, with the
drying material in the receiver or accumulator hold
ing tightly onto the tiny droplets of residual mois-
ture. -
That the attraction of the drying material for
mositure is so powerful that if the receiver or ac-
cumulator is left open, moisture will be drawn in
from the outside air.
That water added to the refrigerant will start
chemical changes that can result in corrosion and
eventual breakdown of the chemicals in the system .
Hydrochloric acid is one result of an R-12 mixture
with water.
That air in the refrigerant system may start reac-
tions that can cause malfunctions .
That the drying agent in the receiver-dehydrator
is Activated Silica Alumina.
That the inert gas in the expansion valve-capilary
line is carbon dioxide.
CONTROLS (FIGURES 23 AND 24)
Combined air conditioning and heating system
controls are located on the instrument panel in the
upper right-hand corner . There are three separate
controls; "FAN" lever, to control speed of blower ;
"OFF," "A/C," "VENT," "HEATER," "DEF"
lever to control direction of air flow and which sys-
tem is to be operated ; "RECIRC," "COLD,"
"HOT" lever to control the temperature of the air.
The three levers may be placed in many combined
positions to deliver the climate conditions most
desirable at any given time.
Figure 23-Air Conditioning Controls, Type 1
OPERATION
.
"Type 1 Fan" (figure 23) -The fan switch has
four positions; "OFF" and three blower speeds rang-
ing from "LO" to "Hl." The fan will not operate
unless the top lever has been moved from the "OFF"
position, and in order to operate the fan in the "HI"
position the engine must be running.
. "Type 2 Fan" (figure 24) -The fan switch has
four positions; "LO" and three blower speeds rang-
ing to "HI" . Fan will operate whenever the key is in
the "RUN" or "ACCESSORY" position . In order to
operate the fan in the "HI" position the engine must
be running.
"OFF", "A/C", "VENT", "HEATER",
"DEF" (figures 23 and 24) - With the lever in the
"OFF" position the system is off, except for the
blower. With the lever in the "A/C" position the air
conditioning system is activated.
With the lever in the "VENT" position, 100%
outside air enters the driver's compartment. This
setting is for use during periods of less severe heat
and humidity, air flow is identical to air flow in
"A/C" position, however, the air conditioning com-
pressor is not operating. Temperature of incoming
air may be controlled by moving the temperature
lever to the desired position . Any one of the blower
speeds may be selected .
Figure 24-Air Conditioning Controls, Type 2