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CONDITION
5.6 UNIT WILL NOT DEFROST PROPERLY - -Continued
Initiates but does not defrost
Frequent defrost
Will not terminate defrost
5.7 ABNORMAL PRESSURES (COOLING)
High discharge pressure
Low suction pressure
Suction and discharge pres-
sures tend to equalize when unit
is operating
5.8 ABNORMAL NOISE OR VIBRATIONS
Compressor
Condenser or Evaporator Fan
5.9 REFRIGERATION CONTROLLER MALFUNCTION
Will not control
POSSIBLE CAUSE
Heater contactor or coil defective
Heater(s) burned out
Wet load
Unit in Emergency Defrost mode
Condenser coil dirty
Condenser fan rotating backwards
Condenser fan inoperative
Refrigerant overcharge or noncondensibles
Discharge pressure regulator valve defective
Discharge service valve partially closed
Suction modulation valve malfunction
Suction service valve partially closed
Filter-drier partially plugged
Low refrigerant charge
Expansion valve defective
No evaporator air flow or restricted air flow
Excessive frost on evaporator coil
Evaporator fan(s) rotating backwards
Discharge pressure regulator valve defective
Suction modulation valve malfunction
Heat exchanger defective
Compressor valves defective
Compressor cycling/stopped
Loose mounting bolts
Worn bearings
Worn or broken valves
Liquid slugging
Insufficient oil
Bent, loose or striking venturi
Worn motor bearings
Bent motor shaft
Defective Sensor
Defective wiring
Fuse (F1, F2) blown
Stepper motor suction modulation valve circuit malfunction
55
REMEDY/
REFERENCE
SECTION
Replace
6.15, page 70
Normal
4.11.2, page 52
6.10, page 66
6.11, page 66
6.11, page 66
6.7.1, page 60
6.19, page 73
Open
6.18, page 71
Open
6.13, page 68
6.7.1, page 60
6.14, page 68
6.15, page 70
5.6, page 54
6.17.1, page 71
6.19, page 73
6.18, page 71
Replace
6.8, page 61
Check
Tighten
6.8, page 61
6.8, page 61
6.14, page 68
6.8.6, page 65
Check
6.11, page 66
6.16, page 70
6.11, page 66
6.16, page 70
6.22, page 75
Check
Replace
6.18, page 71
T-305
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Table of Contents
Troubleshooting
