Carrier 69NT40-561-300, Operation And Service Manual

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T-365 6–4
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 Section 7.12
Low refrigerant charge Section 7.3
No evaporator air flow or restricted air flow Section 7.13
Excessive frost on evaporator coil Section 6.6
Evaporator fan(s) rotating backwards Section 7.14.3
EEV control malfunction Replace
Failed digital unloader valve (DUV) Replace
Suction and discharge pressures
tend to equalize when unit is oper-
ating Compressor operating in reverse Section 6.14
Compressor cycling/stopped Check
Failed digital unloader valve (DUV) Replace
6.8 ABNORMAL NOISE OR VIBRATIONS
Condition Possible Cause Remedy/Refer-
ence Section
Compressor
Compressor start up after an extended shutdown
Normal
Brief chattering when manually shut down
Compressor operating in reverse Section 6.14
Loose mounting bolts or worn resilient mounts Tighten/Replace
Loose upper mounting Section 7.8.1
Liquid slugging Section 7.13
Condenser or Evaporator Fan
Bent, loose or striking venturi Check
Worn motor bearings Section 7.11 /
Section 7.14
Bent motor shaft Section 7.11 /
Section 7.14
6.9 MICROPROCESSOR MALFUNCTION
Condition Possible Cause Remedy/Refer-
ence Section
Will not control
Incorrect software and/or controller configuration Check
Defective sensor Section 7.24
Defective wiring Check
Low refrigerant charge Section 7.3
6.7 ABNORMAL PRESSURES
Condition Possible Cause Remedy/Refer-
ence Section