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

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T-365 6–2
6.3 UNIT RUNS BUT HAS INSUFFICIENT COOLING
Condition Possible Cause Remedy/Refer-
ence Section
Refrigeration system
Abnormal pressures Section 6.7
Abnormal temperatures Section 6.15
Abnormal currents Section 6.16
Controller malfunction Section 6.9
Evaporator fan or motor defective Section 7.14
Compressor service valves or liquid line shutoff valve par-
tially closed Open valves
completely
Frost on coil Section 6.10
Digital unloader valve stuck open Section 7.21.1
Electronic expansion valve Section 7.16.1
6.4 UNIT WILL NOT HEAT OR HAS INSUFFICIENT HEATING
Condition Possible Cause Remedy/Refer-
ence Section
No operation of any kind
Start − Stop switch OFF or defective Check
Circuit breaker OFF or defective Check
External power source OFF Turn ON
No control power
Circuit breaker or fuse defective Replace
Control Transformer defective Replace
Evaporator fan internal motor protector open Section 7.14
Heat relay defective Check
Heater termination thermostat open Section 7.13
Unit will not heat or has insufficient
heat
Heater(s) defective Section 7.13
Heater contactor or coil defective Replace
Evaporator fan motor(s) defective or running backwards Section 7.13 /
Section 7.14
Evaporator fan motor contactor defective Replace
Controller malfunction Section 6.9
Defective wiring Replace
Loose terminal connections Tighten
Low line voltage Section 3.3