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TM 5-4120-287-15
Section V TROUBLESHOOTING
3-12. General
This section provides information useful in diagnosing and correcting unsatisfactory operation or failure of the air
conditioner and its conditioner and its components. Each trouble symptom stated is followed by a list of probable causes.
The possible remedy recommended is described opposite the probable causes. Any trouble beyond the scope of
organizational maintenance shall be reported to direct support maintenance.
3-13. Air Conditioner Fails to Start
No operation in any control position.
Probable cause
Possible remedy
Interrupted power supply
Check line side of power cable. If not reading, check main
power supply.
Main power cable not properly secured, or
Check power input cable and check (J101 and P101) for
cable damaged.
Continuity and positive connection.
Fuse Blown
Replace fuse (para 309).
Power supply our of phase.
Correct phasing of power supply (para 2-4a(6)).
3-14. Insufficient Cooling
Air conditioner operating with air conditioning switch in COOL position.
Probable cause
Possible remedy
Remote control box temperature control
Move variable resistor further down the scale toward COOL
variable resistor set above ambient
position .
Condenser assembly, or inlet filter obstructing air flow
Check condenser section filter clean indicator; service
condenser assembly and inlet filter as required (para 3-33, and
3-35).
Evaporator air inlet filter obstructing air flow
Check evaporator filter clean indicator; service evaporator
assembly and inlet filter as required (para 3-32 and 3-34).
Low refrigerant-12 charge.
Check refrigerant liquid sight indicator; notify direct support
maintenance if flow through indicator appears milky or contains
bubbles (para 2-9c(1).
Compressor and/or condenser drive motors shut down
Allow a few minutes for motor windings to cool down; then press
system reset switch.
Condenser or evaporator fan motors shut down
Internal motor overload relay tripped. Motor will start up auto-
matically when cooled. Notify direct support maintenance if
motor does not restart in a few minutes.
Defective thermostat
Replace thermostat (para 3-39)
Defective remote control
Replace remote control box assemble and/or wiring harness.
3-15. Air conditioning stops
Probable cause
Possible remedy
Power failure
Inspect power source cable for defects or external power source
for proper operation.
Fuse blown
Replace fuse (para 3-9)
Master circuit breaker tripped
Set master circuit breaker to OFF position; after a few minutes
set to ON position. If air conditioner does not start notify direct
support maintenance.
Trip relay K101 energized.
Press system reset switch.
3-16. Compressor Noisy
Probable cause
Possible remedy
Insufficient oil or refrigerant supply, or
Notify direct support maintenance.
defective compressor.
3-17. Compressor Stops
Probable cause
Possible remedy
Condenser or condenser air inlet filter dirty.
Check condenser section filter clean indicator; service or replace
filter and clean condenser and sub-cooler assembly as required
(para 3-33).
Air in refrigerant system
Check refrigerant liquid sight indicator; if refrigerant flow
appears milky or contains bubbles notify direct support
maintenance.
3-10
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