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TM 5-4120-270-15
CHAPTER 5
GENERAL MAINTENANCE INSTRUCTIONS
Section I. SPECIAL TOOLS AND EQUIPMENT
5-1.
Special Tools and Equipment
No special tools or equipment are required to perform
direct and general support and depot maintenance on
the air conditioner.
5-2.
Specially Designed Tools and Equipment No
specially designed tools and equipment are required
to perform direct and general support and depot
maintenance on the air conditioner.
Section II. TROUBLESHOOTING
5-3.
General
This section provides information useful in diagnosing
and correcting unsatisfactory operation or failure of the
air conditioner or any of its components. Each trouble
symptom stated is followed by a list of probable causes.
The possible remedy recommended is described
opposite the probable cause.
5-4.
Compressor Fails to Start
Probable cause
Probable
remedy
Defective selector switch
Test selector switch (para
6-2).
Replace
if
defective.
Defective circuit breaker
Test circuit breaker (para
6-4).
Replace
if
defective.
Defective compressor
Test contactor (para 6-6).
motor contactor
Replace if defective.
Defective time delay relay
Test time delay relay (pars
6-6).
Replace
if
defective.
Defective compressor motorTest relay (para 6-6). Re
protective relay
place compressor if relay
is defective (para 5-24).
Open or shorted control
Perform continuity tests
circuits
(para 612). Repair or
replace defective com-
ponent
Defective compressor motor
Test compressor or motor
(para 626). Replace
compressor if motor is
defective (para 5-24).
Compressor damaged
Replace compressor (para
internally 5-24).
Defective control circuitTest transformer (pars 6
transformer
7).Replace if defective
Defective control circuit
Test rectifier (para 6-8).
Rectifier
Replace if defective.
Defective RFI filters
Test filters (para 68).
Replace if defective.
Shorted control coil in hot
Test control coil (para 6
gas bypass solenoid valve
18). Repair or replace if
defective.
5-5.
Compressor Starts Normally, but Stops on
Overload
Probable cause
Probable remedy
Incorrectly set or defec
Set thermal expansion
tive thermal expansion
valves to correct super-
valves
heat (para 6-17). Re-
place thermal expansion
valves if correct adjust-
ment cannot be obtained
or if valves fail to mod-
ulate refrigerant flow
correctly.
Defective liquid line or
Test control coils (para 6
hot gas line solenoid
18). Check valves for
valves
positive opening and
closing. Replace solenoid
valves if defective.
Bent or kinked refriger-
Visually inspect all tubing
ant tubing
for
damage.
Replace
dam-
aged sections (para 6-16).
Overcharge of refrigerant_
Carefully open pressure line
access valve with air con-
ditioner operating and
bleed excess refrigerant
(para 6-28).
5-6.
Reduced Cooling Capacity
Probable cause
Probable
remedy
Dirty, clogged or damaged
Clean evaporator coil (pars
evaporator coil
623). Repair or replace
if damaged.
Evaporator coil frosting
Adjust back pressure regulat-
ing valve to specification
(pars 6-20). Replace valve
if correct adjustment can-
not be obtained.
Insufficient refrigerant in
Test, evacuate and recharge
system
system (para 6-28, 29, 30).
Defective temperature con-
Test thermostat (para 6-3).
trol thermostat
Replace if defective
5-1
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