Case 580SR Service Manual page 801

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PERFORMANCE TEST EXAMPLE 10
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6
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1. High side normal
2. High side hand valve closed
3. High side hose connected to high side service
connector
4. Not used
PROBLEM
Compressor cycles (cuts in and out) too rapidly.
CAUSE
Thermostatic switch defective.
CONDITIONS*
Low side pressure readings too high during both ON
and OFF compressor cycles and between cycles.
Readings should be:
0.8-1.0 bar - cycle (OFF)
2.5-2.7 bar - cycle (ON)
1.7-1.9 bar - between cycles.
High side pressure normal. Gauge should read
13.3-14.8 bar.
CORRECTIVE PROCEDURES
1. Stop engine and shut off A/C.
2. Replace thermostatic switch with switch of same
type.
SECTION 50 - CAB HEATING AND AIR CONDITIONING
A
B
Performance Test Example 10
4
5. Low side hose connected to low side service
connector
6. Low side hand valve closed
7. Low side gauge
Compressor cycles on at 2.3 bar
Compressor cycles off at 1.9 bar
3. Make sure the switch's temperature sensor is in-
stalled in the same position and depth (in evap-
orator core) as previous.
4. Performance test the system.
DIAGNOSIS
Defective thermostatic switch.
NOTE: * test procedure based upon ambient tem-
perature of 35 °C.
For proper high side gauge reading for other ambi-
ent temperatures, refer to the pressure temperature
chart.
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