Carrier Streamline Scroll 69NT20-531-300 - Manual (Page 61)

5-2 T-309
CONDITION POSSIBLE CAUSE
REMEDY/
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-
tially closed
Open valves
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 No operation of any kind
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 No control power
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
Unit will not heat or has insuffi-
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
Unit fails to stop heating
Heater termination thermostat remains closed along with
the heat relay
6.15
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 Will not initiate defrost
automatically
Defrost temperature sensor defective or heat termination
thermostat open
Replace
Heater contactor or coil defective Replace