3-3
INDICATION/
REFERENCE
TROUBLE
POSSIBLE CAUSES
SECTION
3.7
ABNORMAL PRESSURES (COOLING)
High discharge pressure
Condenser coil dirty
4.17
Condenser fan rotating backwards
4.18
Condenser fan inoperative
4.18
Refrigerant overcharge or noncondensibles
4.6
Discharge pressure regulator valve
Replace
Low suction pressure
Suction service valve partially closed
Open
Filter-drier partially plugged
4.12
Low refrigerant charge
4.4/4.6
Expansion valve defective
4.26
No evaporator air flow or restricted air flow
3.10
Excessive frost on evaporator coil
3.6
Evaporator fan(s) rotating backwards
4.16/4.27
Discharge pressure regulator valve
Replace
Suction and discharge pressures
Heat exchanger defective
Replace
tend to equalize when unit
Compressor valves defective
4.8
is operating
Compressor cycling/stopped
Check
3.8
ABNORMAL NOISE OR VIBRATIONS
Compressor
Loose mounting bolts
Tighten
Worn bearings
4.7
Worn or broken valves
4.7
Liquid slugging
3.11
Insufficient oil
4.10
Condenser or
Bent, loose or striking venturi
Check
Evaporator Fan
Worn motor bearings
4.15/4.18
Bent motor shaft
4.15/4.18
3.9
TEMPERATURE CONTROLLER MALFUNCTION
Will not control
Defective Sensor
4.23
Defective wiring
Check
Fuse (F1, F2) blown
Replace
3.10 NO EVAPORATOR AIR FLOW OR RESTRICTED AIR FLOW
Evaporator coil
Frost on coil
3.6
blocked
Dirty coil
4.14
No or partial
Evaporator fan motor internal protector open
4.15
evaporator air flow
Evaporator fan motor(s) defective
4.15/4.27
Evaporator fan(s) loose or defective
4.15
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