Carrier 69NT40-489-100 Series, Operation And Service Manual

Page: 79 / 178

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