Unit Will Not Heat Or Has Insufficient Heating; Unit Will Not Terminate Heating; Unit Will Not Defrost Properly - Carrier TRANSICOLD 69NT20-274 Operation And Service

INDICATION/
TROUBLE

3.4 UNIT WILL NOT HEAT OR HAS INSUFFICIENT HEATING

No power to unit
No control power
Unit will not heat or
has insufficient heat

3.5 UNIT WILL NOT TERMINATE HEATING

Unit fails to stop
heating

3.6 UNIT WILL NOT DEFROST PROPERLY

Will not initiate
defrost automatically
Will not initiate
defrost manually
Initiates but relay
(DR) drops out
Initiates but does not
defrost
Frequent defrost
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POSSIBLE CAUSES
Start-Stop switch OFF or defective
Circuit breaker OFF or defective
External power source OFF
Circuit breaker or fuse defective
Transformer defective (TR)
Condenser fan internal motor protector open
Evaporator fan internal motor protector open
Heat relay defective
Heater termination switch open
Heater(s) defective
Heater contactor or coil defective
Evaporator fan motor(s) defective or rotating backwards
Evaporator fan motor contactor defective
Temperature controller malfunction
Defective wiring
Loose terminal connections
Low line voltage
Temperature controller improperly set
Temperature controller malfunction
Heater termination switch remains closed along with the
heat relay
Defrost timer malfunction
Loose terminal connections
Defective wiring
Defrost termination or heat termination switch open
Heater contactor or coil defective
Manual defrost switch defective
Defrost termination switch open
Low line voltage
Heater contactor or coil defective
Heater(s) burned out
Wet load
search engine
3-2
REFERENCE
SECTION
Check
Check
Turn on
Replace
Replace
4.17
4.14
Check
4.13
4.15
Replace
4.14/4.27
Replace
3.9
Replace
Tighten
1.5
Reset
3.9
4.13
1.13.4
Tighten
Replace
4.13
Replace
Replace
2.4.3
1.5
Replace
4.15
Normal