5−3
T-364
CONDITION POSSIBLE CAUSE
REMEDY/
REFERENCE
SECTION
5.6 UNIT WILL NOT DEFROST PROPERLY (Continued)
Initiates but does not defrost
Heater contactor or coil defective Replace
Heater(s) burned out 6.13
Frequent defrost Wet load Normal
5.7 ABNORMAL PRESSURES
High discharge pressure
Condenser coil dirty 6.10
Condenser fan rotating backwards 6.11
Condenser fan inoperative 6.11
Refrigerant overcharge or noncondensibles 6.3
Discharge service valve partially closed Open
Electronic expansion valve (EEV) control malfunction Replace
Low suction pressure
Incorrect software and/or controller configuration Check
Failed suction pressure transducer (SPT) or evaporator
pressure transducer (EPT)
Replace
Suction service valve partially closed Open
Filter drier partially plugged 6.12
Low refrigerant charge 6.3
No evaporator air flow or restricted air flow 6.13
Excessive frost on evaporator coil 5.6
Evaporator fan(s) rotating backwards 6.14.3
EEV control malfunction Replace
Failed digital unloader valve (DUV) Replace
Suction and discharge pres-
sures tend to equalize when unit
is operating
Compressor operating in reverse 5.12
Compressor cycling/stopped Check
Failed digital unloader valve (DUV) Replace
5.8 ABNORMAL NOISE OR VIBRATIONS
Compressor
Compressor start up after an extended shutdown
Normal
Brief chattering when manually shut down
Compressor operating in reverse 5.12
Loose mounting bolts or worn resilient mounts Tighten/Replace
Loose upper mounting 6.8.1
Liquid slugging 6.13
Condenser or Evaporator Fan
Bent, loose or striking venturi Check
Worn motor bearings 6.11/6.14
Bent motor shaft 6.11/6.14
5.9 MICROPROCESSOR MALFUNCTION
Will not control
Incorrect software and/or controller configuration Check
Defective sensor 6.22
Defective wiring Check
Low refrigerant charge 6.3
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