Sight Glass; Discharging System; Evacuating System - Jeep 1979 CJ-5 Technical & Service Manual

3E-B AIR CONDITIONING
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A sight glass Is Incorporated In the receiver-to-evapo-
rator hose at the receiver end (fig. 3E-4) or in the top of
the receiver/drier. The sight glass provides a visual
check of the system refrigerant level A continuous
stream of bubbles will appear in the sight glass of a
system which is NOT properly charged. Properly
charged and completely discharged systems will appear
similar through the sight glass because of .a lack of
bubbles. To distinguish between the two situations;
cycle the magnetic clutch OFF and ON with the engine
running at 1500 rpm. During the time the clutch is off,
bubbles will appear if the refrigerant is in the system
and will disappear when the clutch is on. If no bubbles
appear when cycling the magnetic clutch, there is no
refrigerant in the system since some bubbles would ap-
pear in a fully charged system. If the system is dis-
charged, it will be necessary to leak test, repair as
required, evacuate, and charge the system.
CAUTIONi Do not allow the refrigerant to rush out, as
the oil in the compressor will be forced out along with it
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SERV5CE
V A L V E
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GAUGE
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i PRESSURE
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Fig. 3E-5 Pressure i n p and KmlMi timm^ G w f l r t l w
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^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ 8 0 1 7 8 1
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CJ CHEROKEE-WAGONEER-TRUCK
Fig. 3E-4 Sigh! Giass
DISCHARGING SYSTEM
Refrigerant should be discharged from the system
before replacing any part in the system except when
servicing the compressor.
(1) Connect pressure gauge and manifold assembly
to proper service valves.
(2) Turn both manifold hand valves to maximum
counterclockwise (open) position.
(3) Open both service valves a slight amount (from
back seated position) and allow refrigerant to discharge
slowly from system (fig. 3E-5).
EVACUATING SYSTEM
A system with the refrigerant removed during repair,
or one that is excessively low on refrigerant must be
evacuated with a vacuum pump before new refrigerant
is installed. The reason for evacuating a system is to
remove any air and moisture that may have entered the
system.
Moisture in any quantity is extremely harmful to the
air conditioning system. Moisture may collect and freeze
in the thermostatic expansion valve orifice, blocking
refrigerant flow and preventing system cooling. Mois-
ture will also react with R-12 to form hydrocholoric acid
which will corrode metal parts of the system. Corrosion
particles may become detached and block the small pas-
sages and orifices in the system.
Unwanted air and moisture are removed from the
system by proper evacuation of the system. A vacuum
pump is used to lower the pressure sufficiently so that
moisture boiling temperature is reduced to a point
where the water will vaporize and can be evacuated
from the system.
Water boils at 212°F at 14.7 psi (sea level). As the
vacuum pump lowers the pressure of the closed air con-
ditioning system, the boiling point of the moisture in the
system will also be lowered. In evacuating the system, it
is necessary to lower the boiling point of any moisture in
the system to a point lower than the ambient (surround-
ing) temperature to ensure that all moisture is boiled