Carrier 69NT20-531-300 manual Unit will not heat or has insuffi

		REMEDY/
CONDITION	POSSIBLE CAUSE	REFERENCE
		SECTION
5.3 UNIT RUNS BUT HAS INSUFFICIENT COOLING
	Abnormal pressures	5.7
	Abnormal temperatures	5.15
	Abnormal currents	5.16
	Controller malfunction	5.9
	Evaporator fan or motor defective	6.17
	Shortage of refrigerant	6.7.1
Refrigeration System
	Suction modulation valve lost track of step count	Power cycle
	Suction modulation valve malfunction	6.20
	Compressor service valves or liquid line shutoff valve par-	Open valves
	tially closed	completely
	Economizer solenoid valve or TXV malfunction	6.14, 6.19
	Unloader valve stuck open	6.19
	Frost on coil	5.10
5.4 UNIT WILL NOT HEAT OR HAS INSUFFICIENT HEATING
	Start-Stop switch OFF or defective	Check
No operation of any kind	Circuit breaker OFF or defective	Check
	External power source OFF	Turn ON
	Circuit breaker or fuse defective	Replace
	Control Transformer defective	Replace
No control power	Evaporator fan internal motor protector open	6.17
	Heat relay defective	Check
	Heater termination thermostat open	6.15
	Heater(s) defective	6.15
	Heater contactor or coil defective	Replace
	Evaporator fan motor(s) defective or rotating backwards	6.15/6.17
Unit will not heat or has insuffi-	Evaporator fan motor contactor defective	Replace
cient heat	Controller malfunction	5.9
	Defective wiring	Replace
	Loose terminal connections	Tighten
	Low line voltage	2.3
5.5 UNIT WILL NOT TERMINATE HEATING
	Controller improperly set	Reset
Unit fails to stop heating	Controller malfunction	5.9
	Heater termination thermostat remains closed along with	6.15
	the heat relay
5.6 UNIT WILL NOT DEFROST PROPERLY
	Defrost timer malfunction (Cd27)	Table 3-5
	Loose terminal connections	Tighten/
Will not initiate defrost	Defective wiring	Replace
automatically
	Defrost temperature sensor defective or heat termination	Replace
	thermostat open
	Heater contactor or coil defective	Replace

T-309 5-2