Unit Runs But Has Insufficient Cooling; Unit Will Not Heat Or Has Insufficient Heating; Unit Will Not Terminate Heating; Unit Will Not Defrost Properly - Carrier Streamline Scroll 69NT20-531-300 Operation & Service Manual

CONDITION

5.3 UNIT RUNS BUT HAS INSUFFICIENT COOLING

Refrigeration System

5.4 UNIT WILL NOT HEAT OR HAS INSUFFICIENT HEATING

No operation of any kind No operation of any kind
No control power No control power
Unit will not heat or has insuffi- Evaporator fan motor contactor defective
Unit will not heat or has insuffi-
cient heat

5.5 UNIT WILL NOT TERMINATE HEATING

Unit fails to stop heating Unit fails to stop heating

5.6 UNIT WILL NOT DEFROST PROPERLY

Will not initiate defrost Will not initiate defrost
automatically
T-309
POSSIBLE CAUSE
Abnormal pressures
Abnormal temperatures
Abnormal currents
Controller malfunction
Evaporator fan or motor defective
Shortage of refrigerant
Suction modulation valve lost track of step count
Suction modulation valve malfunction
Compressor service valves or liquid line shutoff valve par-
tially closed
Economizer solenoid valve or TXV malfunction
Unloader valve stuck open
Frost on coil
Start-Stop switch OFF or defective
Circuit breaker OFF or defective
External power source OFF
Circuit breaker or fuse defective
Control Transformer defective
Evaporator fan internal motor protector open
Heat relay defective
Heater termination thermostat open
Heater(s) defective
Heater contactor or coil defective
Evaporator fan motor(s) defective or rotating backwards
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
5-2
REMEDY/
REFERENCE
SECTION
5.7
5.15
5.16
5.9
6.17
6.7.1
Power cycle
6.20
Open valves
completely
6.14, 6.19
6.19
5.10
Check
Check
Turn ON
Replace
Replace
6.17
Check
6.15
6.15
Replace
6.15/6.17
Replace
5.9
Replace
Tighten
2.3
Reset
5.9
6.15
Table 3-5
Tighten/
Replace
Replace
Replace