Case 580SR, Service Manual

Page: 796 / 1068

36 SECTION 50 - CAB HEATING AND AIR CONDITIONING
PERFORMANCE TEST EXAMPLE 5
Performance Test Example 4
1. High side high
2. High side hand valve closed
3. High side hose connected to high side service
connector
4. Not used
5. Low side hose connected to low side service
connector
6. Low side hand valve closed
7. Low side high
PROBLEM
Little or no cooling. Engine overheats in some cas-
es.
CAUSE
Condenser not functioning properly.
CONDITIONS*
Low side pressure too high. Gauge should read 1-2
bar.
High side pressure too high. Gauge should read
13.3-14.8 bar.
Liquid line hot.
Evaporator air warm.
High pressure switch cutting out.
CORRECTIVE PROCEDURES
1.
Check belt. Loose or worn drive belts could
cause excessive pressures in the compressor
head.
2. Look for clogged passages between the con-
denser fins and coil, or other obstructions that
could reduce condenser airflow.
3. If engine is overheating replace engine thermo-
stat and radiator pressure cap.
At this point, operate the system and check its per-
formance. If still unsatisfactory, proceed as follows:
4. Discharge and recover the refrigerant from the
system.
5. Remove the condenser and clean and flush it to
ensure a free flow of refrigerant. Or, if the con-
denser appears to be unduly dirty or plugged,
replace it.
6. Replace receiver/drier.
7. Evacuate the system, and recharge it with the
correct quantity of refrigerant.
8. Performance test the system.
DIAGNOSIS
Lack of cooling caused by pressure that is too high
on the high side, resulting from improper operation
of condenser. (Refrigerant charge may be normal or
excessive).
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.
1
2
3
4
7
6
5
F28701
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