Carrier PrimeLINE Operation And Service Manual page 117

Condition
6.3 Unit Runs but has Insufficient Cooling
Refrigeration system
6.4 Unit will not Heat or has Insufficient Heating
No operation of any kind
No control power
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
Possible Cause
Abnormal pressures
Abnormal temperatures
Abnormal currents
Controller malfunction
Evaporator fan or motor defective
Compressor service valves or liquid line shutoff valve
partially closed
Frost on coil
Digital unloader valve stuck open
Electronic expansion valve
Start-Stop switch (ST) 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)
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
termination thermostat open
Heater contactor or coil defective
6–3
defective or rotating
defective or heat
Remedy / Reference
Section 6.7
Section 6.16
Section 6.17
Section 6.9
Section 7.17
Open valves completely
Section 6.10
Replace
Replace
Check
Check
Turn ON
Replace
Replace
Section 7.17
Check
Section 7.15
Section 7.16
Replace
Section 7.17
Replace
Section 6.9
Replace
Tighten
Section 3.3
Reset
Section 6.9
Section 7.15
Table 4–4
Tighten
Replace
Replace
Replace
T-362