Chrysler DODGE D150 1993 Service Manual page 1455

24 - 18 HEATING AND AIR CONDITIONING
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the system when it is opened for repair or replace­
ment of lines or components, The following precau­
tions must be observed.
The system must be completely discharged before
opening any fitting or connection in the refrigeration
system. Open fittings with caution even after the
system has been discharged. If any pressure is no­
ticed as a fitting is loosened, allow trapped pressure
to bleed off very slowly.
Keep the radius of all bends at least 10 times the
diameter of the hose. Sharper bends will reduce the
flow of refrigerant. The flexible hose lines should be
routed so they are at least 80 mm (3 inches) from the
exhaust manifold. It is a good practice to inspect all
flexible hose lines at least once a year to make sure
they are in good condition and properly routed.
Unified plumbing connections with aluminum-N-
gaskets cannot be serviced with O-rings. These gas­
kets are not reusable and do not require lubrication
before installing.
The use of correct wrenches when making connec­
tions is very important. Improper wrenches or im­
proper use of wrenches can damage the fittings.
The internal parts of the refrigeration system will
remain in a state of chemical stability as long as
pure-moisture-free R-12 and refrigerant oil is used.
Abnormal amounts of dirt, moisture or air can upset
the chemical stability and cause operational troubles
or even serious damage if present in more t h a n
minute quantities.
When it is necessary to open the refrigeration sys­
tem, have everything needed ready so the system
will not be left open any longer t h a n necessary. Cap
or plug all lines and fittings as soon as they are
opened to prevent the entrance of dirt and moisture.
All tools, including the refrigerant dispensing man­
ifold, the manifold gauge set and test hoses should be
kept clean and dry.
PRESSURE GAUGE AND MANIFOLD ASSEMBLY
Pressure Gauge and Manifold Assembly Tool
C-3740-A is the most important tool used to service
the air conditioning system (Fig. 1).
COMPONENTS
E¥AP0RAT0R SUCTiOl GAUiE
The left side of the manifold set is calibrated to
register 0 to -100 k P a g (0 to 30 inches of vacuum).
The gauge will also register 0 to 1 000 k P a g (0 to
150 psig). This gauge is connected to the suction ser­
vice port of the compressor. A special service port
adapter, supplied with the gauge set, provides the
means of connecting the gauge set manifold hose to
the service port. When the adapter is installed at the
port and tightened, the stem of the valve in the ser­
vice port is depressed, opening the service port valve.
COMPOUND GAUGE HIGH SIDE
Fig. 1 Pressure Gauge and Manifold Assembly Tool
C-3740-A
DISCHARGE PRESSURE GAUGE
The center of the manifold set is calibrated to reg­
ister 0-2 100 kPag (0-300 psig). For all tests this
gauge is connected to the discharge service port of
the system. The needle valve, located below the dis­
charge pressure gauge, is used to damp out gauge
needle oscillations so t h a t accurate readings can be
obtained.
CENTER MANIFOLD OUTLET
This outlet provides the necessary connection for a
long service hose. This hose is used:
• To discharge the system.
• For a vacuum pump to pull a vacuum before
charging the system.
• For connecting the supply of refrigerant when
charging the system.
MANIFOLD GAUGE WALWES
This valve should be closed when connecting the
gauge set manifold to the service ports of the com­
pressor. The suction gauge valve at the left is opened
to provide a passage between the suction gauge and
the center manifold outlet. The discharge gauge
valve at the right is opened to provide a passage be­
tween the discharge pressure gauge and the center
manifold outlet.
SERVICE VALVES
The discharge (high pressure) and inlet (suction)
service valves are used for diagnosis, charging, dis­
charging and evacuating the system.
CONNECT PRESSURE GAUGE AND MANIFOLD
ASSEMBLY
Remove the protective caps from the service valve
gauge ports and valve stems.
Close both of the hand valves on the gauge mani­
fold set.