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

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6–3 T-365
6.5 UNIT WILL NOT TERMINATE HEATING
Condition Possible Cause Remedy/Refer-
ence Section
Unit fails to stop heating
Controller improperly set Reset
Controller malfunction Section 6.9
Heater termination thermostat remains closed along with
the heat relay Section 7.13
6.6 UNIT WILL NOT DEFROST PROPERLY
Condition Possible Cause Remedy/Refer-
ence Section
Will not initiate defrost automati-
cally
Defrost timer malfunction (Cd27) Section Table 4–
3
Loose terminal connections Tighten
Defective wiring Replace
Defrost temperature sensor defective or heat termination
thermostat open Replace
Heater contactor or coil defective Replace
Will not initiate defrost manually
Keypad is defective Replace
Defrost temperature sensor open Replace
Initiates but relay (DR) drops out Low Line Voltage Section 3.3
Initiates but does not defrost
Heater contactor or coil defective Replace
Heater(s) burned out Section 7.13
6.7 ABNORMAL PRESSURES
Condition Possible Cause Remedy/Refer-
ence Section
High discharge pressure
Condenser coil dirty Section 7.10.1
Condenser fan rotating backwards Section 7.10
Condenser fan inoperative Section 7.11
Refrigerant overcharge or non-condensibles Section 7.3
Discharge service valve partially closed Open
Electronic expansion valve (EEV) control malfunction Replace