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WARNING
Extreme care must be taken to ensure that
all the refrigerant has been removed from
the compressor crankcase or the resultant
pressure will forcibly discharge compres-
sor oil.
2. Drain or pump out compressor oil until the level is
brought to the proper level.
3. Evacuate the compressor to 500 microns. Backseat
the compressor service valves and repeat the oil lev-
el check procedure.
f. To add oil to the compressor, do the following:
1. With the system off, connect a manifold gauge set to
the compressor suction and discharge service
valves. Front seat both service valves to isolate the
compressor from the system (See Figure 4--5) and
reclaim the refrigerant to below atmospheric pres-
sure. Shut off the reclaimer and verify the pressure
does not rise. If the pressure rises, continue reclaim-
ing until the pressure remains below atmospheric.
2. Add oil to compressor crankcase slowly, through the
oil fill plug opening (see Figure 4--14) to bring level to
mid range of allowed levels.
3. Evacuate compressor to 500 microns. Backseat
compressor suction and discharge valves, start sys-
tem and recheck oil level.
4. Remove manifold gauge set.
4.15.4 Compressor Electric Unloader Operation
To check unloader operation do the following:
a. Install a manifold gauge set (Refer to Figure 4--6).
b. Start the unit and allow it to stabilize in High Speed
Cool.
c. Insure that the unloaders are de--energized. Com-
pressor is fully loaded, 6 cylinder operation.
d. Slowly front--seat the suction se4rvice valve. The
suction pressure will begin to fall.
e. Watch the suction gauge on the manifold gauge set.
When the suction pressure gauge "jumps" (3 to 5 psi--
0.2 to 0.4 bar) note the pressure at which the gauge
jumped in the chart below. Unloader solenoid coil #1
has been energized and the compressor is now in 4
cylinder operation.
f. Continue to slowly front--seat the suction service
valve and watch the suction gauge. When the suction
pressure gauge "jumps" (3 to 5 psi-- 0.2 to 0.4 bar)
note the pressure at which the gauge jumped in the
chart below. Unloader solenoid coil #2 has been ener-
gized and the compressor is now in 2 cylinder opera-
tion.
g. Slowly back--seat the suction service valve. The suc-
tion pressure will begin to rise.
h. Watch the suction gauge on the manifold gauge set.
When the suction pressure gauge "jumps" (3 to 5 psi--
0.2 to 0.4 bar) note the pressure at which the gauge
jumped in the chart below. Unloader solenoid coil #2
05/09
has been de--energized and the compressor is now in
4 cylinder operation.
i. Continue to slowly back--seat the suction service
valve and watch the suction gauge. When the suction
pressure gauge "jumps" (3 to 5 psi-- 0.2 to 0.4 bar)
note the pressure at which the gauge jumped in the
chart below. Unloader solenoid coil #1 has been de--
energized and the compressor is now in 6 cylinder op-
eration.
j. Compare these values to the one in your service
manual (Table 1--3).
PRESSURE
COIL ENERGIZED
READING
UNLOADER #1
UNLOADER #2
Approximate Unloader Coil Resistance:
12VDC Coil = 10.2 Ohms
24VDC Coil = 40.0 Ohms
4.16 TEMPERATURE SENSOR CHECKOUT
a. An accurate ohmmeter must be used to check resist-
ance values shown in Table 4--1.
b. Due to variations and inaccuracies in ohmmeters,
thermometers or other test equipment, a reading
within two percent of the chart value would be consid-
ered acceptable. If a sensor is bad, the resistance val-
ue would usually be much higher or lower than the
value given in Table 4--1.
c. At least one sensor lead must be disconnected from
the controller before any reading can be taken. Not
doing so will result in a false reading. Two preferred
methods of determining the actual test temperature
at the sensor are an ice bath at 32°F (0°C) and/or a
calibrated digital temperature meter.
Table 4- -1 Temperature Sensor Resistance
Temperature
°
°
F
C
14
-10
23
- 5
32
0
41
5
50
10
59
15
68
20
77
25
86
30
95
35
104
40
113
45
122
50
131
55
140
60
4--13
COIL DE- -ENER-
UNLOADED
GIZED LOADED
Resistance In Ohms
55,304
42,316
32,650
25,394
19,903
15,713
12,493
10,000
8,056
6,531
5,325
4,367
3,601
2,986
2,488
T-336
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