Pressure Gauge And Manifold Assembly; Checking System Pressures (Air Conditioning) - Jeep 1979 CJ-5 Technical & Service Manual

8E-4 AIR C0N01T10NING
When the valve is midpositioned (cracked) (fig. 3E-2,
View C), the gauge port is open. This position is used
when charging, discharging, evacuating, and checking
system pressure.
PRESSURE GAUGE AND MANIFOLD ASSEMBLY
The Pressure Gauge and Manifold Assembly, tool J-
23575 (fig. 3E-3), is the most important tool used to
service the air conditioning system. The gauge assembly
is used to determine system high and low side gauge
pressures, the correct refrigerant charge, and in system
diagnosis. It is designed to provide simultaneous high
and low side pressure indications, because these pres-
sures must be compared to determine correct system
operation.
COMPOUND GAUGE H I G H SIDE GAUGE
M A N I F O L D
Fig. 3E-3 Pressure Gauge and Manifold Assembly, Tool J-23575
Low Side Gauge
The low side gauge is a compound gauge, which means
that it will register both pressure and vacuum. The
compound gauge is calibrated 0 to 150 psi pressure and 0
to 30 inches of mercury vacuum. It is connected to the
suction service valve to check low side pressure or
vacuum.
High S i t Giuge
The high side gauge is used to check pressure in the
discharge side of the air conditioning system.
Manifold
The gauges are connected into the air conditioning
system through a manifold (fig. 3E-3). The manifold has
three connections. The low side hose and fitting is con-
nected directly below the low side gauge. The high side
hose and fitting is connected below the high side gauge.
The center connection of the manifold is used for
charging, discharging and evacuating. Both the high and
low sides of the manifold have hand shutoff valves. The
hand shutoff valves open or close the respective gauge
connections to the center service connection or to each
other. The manifold is constructed so that pressure will
be indicated on the gauges regardless of hand valve
position.
Connecting the Pressure Gauge and Manifold Assembly
(1) Remove protective caps from service valve
gauge ports and valve stems.
(2) Close both hand valves on gauge manifold set.
(3) Connect compound gauge hose (blue) to com-
pressor suction service valve gauge port (low side).
(4) Connect high pressure gauge hose (red) to dis-
charge service valve gauge port (high side).
N O T E : If necessary, to facilitate installation of the
gauge set, loosen the service valve-to-compressor fitting
and rotate the service valve slightly. Do not allow line
to contact engine or body components. Tighten the serv-
ice valve-to-compressor fitting to 25 foot-pounds (34
N®m) torque or 15 foot-pounds (20 N«m) torque for
flange type service valve screws.
(5) Set both service valve stems to mid- or cracked
position. The gauges will indicate high and low side
pressures respectively.
(6) Purge any air from high side test hose by open-
ing high side hand valve on manifold for 3 to 5 seconds
(center connection on manifold must be open).
(7) Purge any air from low side test hose by opening
low side hand valve on manifold for 3 to 5 seconds
(center connection on manifold must be open).
(8) Air conditioning system may be operated with
gauge manifold assembly connected in this manner.
Gauges will indicate respective operative pressures.
CHECKING SYSTEM PRESSURES
The pressure developed on the high side and low side
of the compressor indicate whether the system is oper-
ating properly.
(1) Attach pressure gauge and manifold assembly.
(2) Close both hand valves on gauge and manifold
assembly.
(3) Set both service h a n d valve , s t e m s to
midposition.
(4) Operate AC system with engine running at 1500
rpm and controls set for full cooling.
. (5) Insert thermometer into discharge air outlet
and observe air temperature.
(6) Observe high and low side pressures and com-
pare with those shown in the Normal Operating Tem-
peratures and Pressures chart. If pressures are
abnormal, refer to Pressure Diagnosis chart.