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24-20
AIR
CONDITIONING
(2) Slowly close the left-hand gauge valve. All air
delivered by the compressor will now be discharged
through the metering orifice in the test cap. Pressure
registered at the discharge gauge should build up to
at least 190 psi (Fig. 21).
(3) The load on the compressor may affect engine
speed. If necessary, readjust engine speed to
exactly
500 rpm. The discharge pressure should build up to
a
minimum of 190 psi.
(4) Open the left-hand gauge valve momentarily to
allow the pressure to drop. Then close the valve to
make sure the pressure again builds up to a minimum
of 190 psi with the engine operating at 500 rpm.
CAUTION: To prevent possible compressor dam-
age from excessive heat, do not operate the com-
pressor more than a total
of five minutes.
If
the compressor does not develop a minimum of
190 psi at 500 engine rpm, both compressor valve
plate assemblies and gaskets must be replaced. See
Paragraph "Compressor."
After repair, the compressor capacity must be
tested before charging the system and repeating the
"Over-All Performance Test."
A compressor that consistently builds up to a mini-
mum of 190 psi at exactly 500 engine rpm is deliver-
ing the rated capacity. Reconnect the evaporator suc-
tion line to the suction muffler and the discharge line
to the discharge muffler. When connecting these lines
use new "0" rings and lubricate both male and fe-
male connections with clean refrigerant oil. Continue
with the "Expansion Valve Test."
TEST 8
EXPANSION VALVE TEST
The following procedure permits testing the expan-
sion valve without removing it from the system. This
test is made with the system completely discharged.
IMPORTANT: It is absolutely necessary for the
compressor to pass the compressor capacity test
be-
fore testing the expansion valve in its installed po-
sition.
A compressor which does not pass the Compressor
Capacity Test may have leaking reed valves
or
a frac-
tured head gasket. Such a leak would allow refriger-
ant gas, used in the Expansion Valve Test, to leak
from the discharge side of the compressor back into
the suction side of the compressor. An internal leak
between the discharge and suction side of the com-
pressor will upset the Expansion Valve Test results.
Test Preparation
und
Connections
(1) Close both the left and right gauge set manifold
valves. Open the manifold needle valve.
(2) Install a
Vi"
connector and a
Vi"
tee fitting at
the left side of the gauge manifold. Install the test
cap (SP-2922) on the tee fitting, and connect the test
hose to the lower end of the tee fitting.
(3) Connect the other end of the suction test hose
to the suction service port, using the special adapter
to keep the suction service valve open.
(4)
Connect the discharge test hose to the discharge
service port, using a special adapter to hold this serv-
ice valve open.
(5) Connect one end of the long test hose to the
center of the gauge manifold, and the other end to
the refrigerant dispensing manifold.
(6) Close two of the dispensing manifold valves
(turn clockwise). Open the remaining dispensing
manifold valve (fully counterclockwise). Remove the
protective cap from the
opened
valve.
(7)
Screw a refrigerant can to the
opened
manifold
valve, and tighten 6 to
8
foot-pounds maximum.
Tighten the manifold locking nut against the shoulder
of the can, again using 6 to
8
foot-pounds maximum
to insure a good seal.
(8)
Turn the manifold valve (about the refrigerant
can)
completely clockwise
to puncture the can. This
also closes the valve and seals the refrigerant in the
can.
This completes all test connections necessary for
the "Expansion Valve Test." Compare the test set-up
against those illustrated in Figure 22.
Then, proceed with the following preparation steps.
(9) Remove the expansion valve thermal bulb from
its well inside the evaporator housing.
(10) Prepare a large pan of water heated to 125 de-
grees F. and place the refrigerant can upright in the
water. Use enough water to provide the heat neces-
sary to insure ample refrigerant pressure throughout
this test.
(11) Prepare a container of ice and water to pro-
vide a known temperature of 32 degrees F. This will
be used to test the expansion valve in its "minimum
flow" position.
NOTE: Under extreme conditions
of
high heat and
humidity the temperature of the ice and water may
not
be reduced to 32 degrees F. Use a thermometer
to test the actual temperature. If it i s necessary to
lower the temperature of the ice and water, add
small quantities of salt while stirring until the de-
sired temperature of
32
degrees
F .
it obtained.
Maximum Flow Test-
Thermal Bulb Wurm
(1) Warm the thermal bulb by holding it in your
hand. This will produce the same effect as
a
warm
evaporator
. . .
it will open the expansion valve for
maximum flow
. .
.
(2) Open the
refrigerant manifold valve
(fully
counterclockwise) to allow the refrigerant vapor to
flow to the gauge set manifold.
(3) Adjust the right-hand gauge set manifold valve
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