Unit Will Not Terminate Heating; Unit Will Not Defrost Properly - Carrier 69NT40-561-019 Operation And Service Manual

CONDITION
Unit will not heat or
has insufficient heat
6.5

UNIT WILL NOT TERMINATE HEATING

Unit fails to stop heating
6.6

UNIT WILL NOT DEFROST PROPERLY

Will not initiate defrost
automatically
Will not initiate
defrost manually
Initiates but relay
(DR) drops out
Initiates but does not defrost
Frequent defrost
6.7 ABNORMAL PRESSURES
High discharge pressure
POSSIBLE CAUSE
Heater(s) defective
Heater contactor or coil defective
Evaporator fan motor(s) defective or rotating backwards
Evaporator fan motor contactor defective
Controller malfunction
Defective wiring
Loose terminal connections
Low line voltage
Controller improperly set
Controller malfunction
Heater termination thermostat remains closed
along with the heat relay
Defrost timer malfunction (Cd27)
Loose terminal connections
Defective wiring
Defrost temperature sensor defective or heat
termination thermostat open
Heater contactor or coil defective
Manual defrost switch defective
Keypad is defective
Defrost temperature sensor open
Low line voltage
Heater contactor or coil defective
Heater(s) burned out
Wet load
Condenser coil dirty
Condenser fan rotating backwards
Condenser fan inoperative
Refrigerant overcharge or noncondensibles
Discharge service valve partially closed
Electronic expansion valve (EEV) control malfunction
6–3
REMEDY/
REFERENCE
SECTION
7.9
Replace
7.9/7.10
Replace
6.9
Replace
Tighten
3.3
Reset
6.9
7.9
Table 4–5
Tighten
Replace
Replace
Replace
Replace
Replace
Replace
3.3
Replace
7.9
Normal
7.6
7.7
7.7
7.3
Open
Replace
T-359