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24-1 6
AIR CONDITIONING
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TEMP
making the over-all performance test is that the en-
gine must be operated at 1250 rpm for approximately
five minutes to allow all the under-hood components
of the system to reach their operating temperature.
Partially
close the needle valve, located below the
discharge pressure gauge, to minimize oscillation of
the pointer. Do not close the needle valve completely
since this would prevent the discharge pressure
gauge from registering pressure.
This
test
should be performed with the discharge
pressure from 190 to 210 psi. The 190 to 210 pound
pressure is for
test purposes only.
To increase pres-
sure restrict the air flow across the condenser using
cardboard, paper, etc. to decrease pressure. Increase
air flow across condenser with external floor fans.
Observe and record both the "Inlet Dry Bulb Tem-
perature" and "Inlet Wet Bulb Temperature" as reg-
istered on the psychrometer.
Observe and record the "Discharge Air Tempera-
ture" registered by the thermometer at the right hand
grille outlet.
From the "Performance Temperature Chart" (Fig.
19), determine the maximum allowable discharge air
temperature for the prevailing "Dry" and "Wet" bulb
temperatures recorded. If the vehicle's discharge air
temperature is at or below the temperature given on
the Performance Chart, the air-conditioning is deliv-
ering its cooling capacity. However, to assure trou-
blefree operation, continue with the "Evaporator
Pressure Regulator," TEST 6.
If the discharge air temperature at the outlet grilles
is above the maximum allowable on the Performance
Chart, perform the following operations in the order
indicated until proper performance is obtained.
(1) "The Evaporator Pressure Regulator Test."
(2) "The Compressor Capacity Test."
(3)
"The Expansion Valve Test."
89
90
63
64
TEST 6
EVAPORATOR PRESSURE REGULATOR
VALVE TEST (AR-1, 2)
TEST 6 is divided into two parts to simplify the
test procedures. As both parts of the
test
must be
made progressively, it is important that both parts be
read thoroughly before proceeding with the
test.
PART 1
The "EPR" valve is calibrated to produce maxi-
mum "cooling" without causing frost
or
ice on the
evaporator fins and tubing. If for any reason the
factory calibration has been disturbed, the "EPR"
valve may restrict the flow of refrigerant at an evap-
orator pressure which is either too high for maximum
performance or too low to prevent coil freeze up.
The evaporator pressure regulator test determines
whether or not the valve is functioning properly.
€PR
V d v e Test Conditions
Normally, this test is performed after completion
of the Over-all Performance Test. The gauge
set
manifold will be connected, as shown in Figure 14.
Adjust engine speed to 1250 rpm. Close the hood
for this test. Open the windows.
Turn the blower switch to position NO. 2 and push
in the "Cool" button.
The heat load on the evaporator will soon call
for
continuous operation of the refrigeration system. The
"EPR" valve will open and the pressure at both the
suction port and the compressor inlet service port
will be approximately the same. It is normal for the
compressor inlet pressure to be slightly lower than
the evaporator suction pressure.
Observe the evaporator suction gauge and the com-
pressor inlet gauge. Both should register
26
psi
or
slightly higher. This indicates that the "EPR" valve
is open. The next step is to determine the minimum
evaporator suction pressure maintained in the suction
line by the "EPR" valve.
The "EPR" valve action can be accelerated by
re-
ducing the heat load on the evaporator. This is accom-
plished by turning the blower switch to position NO.
1 ("Low-Speed"), thus reducing the volume
of air
passing through the evaporator. Immediately the
evaporator will start to get colder. It is necessary to
I
1963 AIR CONDITIONING PERFORMANCE CHART
I
I
WET BULB INLET AIR TEMPERATURE
I
Fig. 19-Performance
Temperature Chart
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