Carrier 69NT40-541-505, Operation And Service Manual, Page: 88 / 143

T-368 6–2
6.3 UNIT RUNS BU HAS INSUFFICIENT COOLING
Condition Possible Cause Remedy/Refer-
ence Section
Compressor Compressor valves defective 7.8
Refrigeration System
Abnormal pressures 6.7
Controller malfunction 6.9
Evaporator fan or motor defective 7.14
Suction modulation valve malfunction 7.17
Condenser Pressure Transducer defective Check
Shortage of refrigerant 7.7.1
6.4 UNIT WILL NOT HEAT OR HAS INSUFFICIENT HEATING
Condition Possible Cause Remedy/Refer-
ence Section
No operation of any kind
Start-Stop switch OFF or defective Check
Circuit breaker OFF or defective Check
External power source OFF Turn ON
No control power
Circuit breaker or fuse defective Replace
Control Transformer defective Replace
Evaporator fan internal motor protector open 7.14
Heat relay defective Check
Heater termination switch open 7.13
Unit will not heat or has
insufficient heat
Heater(s) defective 7.13
Heater contactor or coil defective Replace
Evaporator fan motor(s) defective or rotating backwards 7.13 / 7.14
Evaporator fan motor contactor defective Replace
Controller malfunction 6.9
Defective wiring Replace
Loose terminal connections Tighten
Low line voltage 3.3
6.5 UNIT WILL NOT TERMINATE HEATING
Condition Possible Cause Remedy/Refer-
ence Section
Unit fails to stop heating
Controller improperly set Reset
Controller malfunction 6.9
Heater termination thermostat remains closed along with
the heat relay
7.13
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