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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