GMC 1976 ZEO 6083 Maintenance Manual page 59

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AIR CONDITIONING SYSTEM
reach a predetermined level high enough to cause
system damage . After the pressure drops to a safe
level the valve will close. After such an occurrence,
the system should be thoroughly checked to discover
and correct the cause of the abnormal pressure in-
crease, and then should be purged, evacuated and
charged.
REFRIGERANT LINES
Special refrigerant hose lines are required to
carry the refrigerant liquid and vapor between the
various system components . The hose line with the
smallest diameter is called the high pressure liquid
line . It is routed from the condenser or receiver-
dehydrator to the evaporator or thermostatic expan-
sion valve. The large diameter hose line connecting
the compressor and evaporator is the low pressure
vapor line . The large diameter hose between the com-
pressor and condenser is the high pressure vapor
discharge line .
These hoses are constructed with a synthetic
material core covered with a woven metal mesh
which is, in turn, covered by a woven fabric and
coated for extra protection . This hose is so con-
structed to withstand the extreme pressures and tem-
peratures found in the modern refrigeration system .
None but special refrigerant type hoses should be used .
All systems make use of swaged type connections
(hose to metal fittings) with metal to metal fittings
being made using "O" rings. Care must be taken
when making these connections that they not be
turned down too tightly or damage to the "O" rings
may result .
Figure 13-Condenser and Receiver-Dehydrator, Type 1
Flexible refrigerant hoses should not be permit-
ted to contact the hot engine manifold nor should
they be bent into a radius of less than 10 times their
diameter.
FAN SLIP CLUTCH
A special engine fan is used. It is a seven bladed
fan, limited by means of a viscous clutch to a max-
imum speed of 3200 rpm, regardless of the speed of
the engine . The silicone fluid in the clutch transmits
only enough torque to drive the fan at this limited
speed, thus avoiding excessive noise and power con-
sumption by the fan at higher engine speeds . A tem-
perature modulating device further limits fan speed
to 1000 rpm until ambient temperature at the modu-
lating device reaches 140°F. at which time fan speed
will be allowed to increase to 3200 rpm. Some adjust-
ment of the modulating device is possible .
CONDENSER
The condenser receives the high pressure, high
temperature gas which is pumped from the compres-
sor and condenses it into a high pressure high tem
perature liquid . The heated gas which enters near the
top of the condenser is cooled by giving off heat to
the metal surfaces of the condenser. The heat is then
extracted from these metal surfaces by the ram air
passing over the condenser.
The condenser is located in front of the engine
cooling system radiator so that it receives a high
volume of air from the movement of the vehicle and
from the engine fan.
The condenser is similar in design to the ordinary
radiator but is designed to withstand much higher
pressures (figure 13).
Figure 14-Location of Receiver Dehydrator, Type 2