Carrier 69NT40-541-505, Operation And Service Manual, Page: 90 / 143

T-368 6–4
6.8 ABNORMAL NOISE OR VIBRATIONS
Condition Possible Cause Remedy/Refer-
ence Section
Compressor
Loose mounting bolts Tighten
Worn bearings 7.8
Worn or broken valves 7.8
Liquid slugging 7.16
Insufficient oil 7.8.6
Condenser or Evaporator Fan
Bent, loose or striking venturi Check
Worn motor bearings 7.11 / 7.14
Bent motor shaft 7.11 / 7.14
6.9 MICROPROCESSOR MALFUNCTION
Condition Possible Cause Remedy/Refer-
ence Section
Will not control
Defective Sensor 7.21
Defective wiring Check
Fuse (F1, F2) blown Replace
Stepper motor suction modulation valve circuit malfunction 7.17
6.10 NO EVAPORATOR AIR FLOW OR RESTRICTED AIR FLOW
Condition Possible Cause Remedy/Refer-
ence Section
Evaporator coil blocked
Frost on coil 6.6
Dirty coil 7.13
No or partial evaporator air flow
Evaporator fan motor internal protector open 7.14
Evaporator fan motor(s) defective 7.14
Evaporator fan(s) loose or defective 7.14
Evaporator fan contactor defective Replace
6.11 THERMOSTATIC EXPANSION VALVE MALFUNCTION
Condition
Possible Cause Remedy/Refer-
ence Section
Low suction pressure with high su-
perheat
Low refrigerant charge 7.7.1
External equalizer line plugged Open
Wax, oil or dirt plugging valve or orifice ice formation at
valve seat
7.16
Superheat too high 7.7.1
Power assembly failure 7.16
Loss of element/bulb charge 7.16
Broken capillary 7.16
Foreign material in valve 7.16
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