Safran PILATUS PC12 M19 User manual

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SYSTEM DESCRIPTION AND
OPERATION MANUAL
WITH ILLUSTRATED PARTS LIST
PILATUS PC12 M19
R-134a AIR CONDITIONING SYSTEM COMPONENTS:
DIRECT DRIVE COMPRESSOR MODULE 1150950-3
(Supersedes 1150950-2)
CONDENSER MODULE w/RECEIVER DRYER 1150970-1
AXIAL CONDENSER FAN 1250435-30
LEFT HAND EVAPORATOR MODULE 1150900-2
RIGHT HAND EVAPORATOR MODULE 1150910-2
ATA SPECIFICATION 21-00-60

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Table 1 Record of Revisions
RE
V
DESCRIPTION OF CH
A
NGE DATE
A
PPRO
V
A
L
ORIGINAL RELEASE 6/24//20 BS

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TABLE OF CONTENTS
1. MANUALINTRODUCTION................................................................................................................................7
1.1. Generalintroduction(HowtoUse):.........................................................................................................7
1.2. Acronyms,Abbreviations,and
Symbols: ..................................................................................................8
1.3. StandardTorque
Values: ..........................................................................................................................9
1.4. Documentsrequired:...............................................................................................................................9
2. SYSTEMDESCRIPTIONANDOPERATION........................................................................................................10
2.1. General:..................................................................................................................................................10
2.2. SystemDescriptionandOperation:.......................................................................................................11
2.3. SystemComponentDescriptionandOperation:...................................................................................12
3. TESTINGANDFAULTISOLATION....................................................................................................................15
3.1. General:..................................................................................................................................................15
3.2. SystemLeakCheckTesting
Procedure: ..................................................................................................15
3.3. FaultIsolation(Trouble‐
Shooting): ........................................................................................................17
4. SYSTEMPLUMBINGDIAGRAM.......................................................................................................................20
4.1. R‐134ARefrigerantFlowSchematic:......................................................................................................20
5. DISASSEMBLY.................................................................................................................................................21
5.1. General:..................................................................................................................................................21
5.2. CondenserModuleDisassemblyProcedures.........................................................................................22
5.3. EvaporatorModuleAssemblyDisassembly
Procedures ........................................................................23
6. CLEANINGPROCEDURES................................................................................................................................24
6.1. General:..................................................................................................................................................24
6.2. CondenserModuleCleaningProcedures:..............................................................................................25
6.3. EvaporatorModuleAssemblyCleaningProcedures:.............................................................................26
7. INSPECTIONSCHEDULE..................................................................................................................................27
7.1. CondenserModuleAssemblyInspection
Schedule: ..............................................................................27
7.2. EvaporatorModuleAssemblyInspectionSchedule:..............................................................................28
8. REPAIRPROCEDURES.....................................................................................................................................30

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8.1. General:..................................................................................................................................................30
8.2. CondenserModuleRepairProcedures:.................................................................................................30
8.3. EvaporatorModuleAssemblyRepairProcedures:................................................................................32
9. ASSEMBLY......................................................................................................................................................34
9.1. General:..................................................................................................................................................34
9.2. CondenserModuleAssemblyProcedures.............................................................................................35
9.3. EvaporatorModuleAssemblyProcedures.............................................................................................36
10. SPECIALTOOLS/EQUIPMENT.....................................................................................................................37
10.1. General:..............................................................................................................................................37
11. ILLUSTRATEDPARTSLISTING.....................................................................................................................38
11.1. Introduction:......................................................................................................................................38
12. SPECIALPRODECURES................................................................................................................................43
12.1. General...............................................................................................................................................43
12.2. Tools,Fixtures,Equipment,orconsumableitemsrequired:.............................................................43
12.3. Evacuatingthesystem.......................................................................................................................44
12.4. Chargingthesystem..........................................................................................................................44
12.5. Flushingthesystem(UseflushingkitpartnumberK1134100‐500)..................................................45
13. STORAGEPROCEDURES.............................................................................................................................47
13.1. General:..............................................................................................................................................47
13.2. SystemLongTermShelfStorage:.......................................................................................................47
13.3. SystemOff‐Season/On‐AircraftFunctionalTests:..............................................................................48
13.4. GeneralSystemComponentStorageprocedures:.............................................................................48

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LIST OF ILLUSTRATIONS
Figure 1 VCS Refrigerant Schematic .................................................................................................... 20
Figure 2 1150900-2 (Left) & 1150910-2 (Right) (1150910-2 Shown) ................................................... 39
Figure 3 1150970-1 Condenser Module ............................................................................................... 41
LIST OF TABLES
Table 1 Record of Revisions ................................................................................................................... 3
Table 2 Standard Torque Values ............................................................................................................ 9
Table 3 Consumable Products ................................................................................................................ 9
Table 4 Trouble-shooting ...................................................................................................................... 18
Table 5 Condenser Module Inspection ................................................................................................. 27
Table 6 Evaporator Inspection .............................................................................................................. 28
Table 7 Evaporator Parts Listing ........................................................................................................... 40
Table 8 Condenser Module Parts Listing .............................................................................................. 42
Table 9 Typical Operating Pressures .................................................................................................... 46

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INTRODUCTION
1. MANUAL INTRODUCTION
1.1. General introduction (How to Use):
1.1.1. This system description and operation manual (SDOM) covers the requirements for field
servicing the R-134A air conditioning system for the Pilatus PC12 M19 aircraft. This
document includes component descriptions, servicing, maintenance, inspection
requirements and an illustrated parts list.
1.1.2. This component maintenance manual has been prepared with guidance from the Air
Transport Association of America (ATA) Specification 2200. The user must not change the
repair methods in this manual without authorization from the aviation authorities and the
manufacturer.
1.1.3. This manual gives the procedures to perform the servicing and maintenance of the
component in a workshop environment as well as on the aircraft. Only approved personnel
with the necessary skills shall perform the maintenance procedures in this manual.
1.1.4. Although Enviro Systems tries to cover all conceivable issues that may arise, there may be
issues that are not covered in this manual. In these cases, please call Enviro Systems
customer service.
1.1.5. Technicians must use the instructions in this manual to do all the maintenance procedures
related to the component. Read all the related warnings, cautions and notes before you
begin work on the components. Warnings, cautions and notes shown in this manual provide
the following information:
WARNING: Discloses vital information in order to prevent injury or death
while performing the maintenance procedure.
CAUTION: Discloses vital information in order to prevent damage to the
equipment during the maintenance procedure.
NOTE: Discloses more information that will help perform a step of the
procedure or refers to a different procedure.
1.1.6. A complete Illustrated Parts Listing (IPL) is supplied as additional documentation (Section
11) to provide service technicians access to exploded views and a parts list while performing
maintenance, testing, disassembly and assembly procedures. Refer to the IPL for all figure
and item numbers.

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1.2. Acronyms, Abbreviations, and Symbols:
• CMM Component Maintenance Manual
• ATA Air Transport Association
• IPL Illustrated Parts Listing
• VCS Vapor Cycle System
• SDS Safety Data Sheet
• PSIG Pressure Per Square Inch, Gage
• SAE Society of Automotive Engineers
• CCW Counter Clockwise
• CW Clockwise
• FOD Foreign Object Damage
• OAT Outside Air Temperature

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1.3. Standard Torque Values:
Table 2 Standard Torque Values
T
Y
PE FASTENER DESCRIPTION
/
LOC
A
TION TORQUE
.25-28 SET SCREW EVAPORATOR BLOWER WHEEL 12-15 IN LBS
6-32 SCREW ALL LOCATIONS 8-10 IN-LBS
8-32 SCREW ALL LOCATIONS 12-15 IN-LBS
10-32 SCREW/BOLT ALL LOCATIONS 20-25 IN-LBS
¼-28-UNF ALL LOCATIONS 50-70 IN-LBS
5/16-24UNF ALL LOCATIONS 100-140 IN-LBS
3/8-24UNF ALL LOCATIONS 160-190 IN-LBS
5/8-18 PLUMBING
CONNECTIONS
RECEIVER DRYER INLET/DISCHARGE
PORT
132-156 IN-LBS
7/8-14 PLUMBING
CONNECTIONS
COMPRESSOR SUCTION PORT 252-324 IN-LBS
¾-16 PLUMBING
CONNECTIONS
COMPRESSOR DISCHARGE PORT 180-240 IN LBS
7/16-20 PLUMBING
CONNECTIONS
EXPANSION VALVE INLET PORT 100-140 IN LBS
¾-16 PLUMBING
CONNECTIONS
EXPANSION VALVE OUTLET PORT 270-350 IN LBS
1.4. Documents required:
• Illustrated Parts Listings (IPL) (included with this manual)
• Pilatus PC12 Aircraft Maintenance Manual
1.5. Consumable
Products:
Table 3 Consumable Products
EN
V
IRO P
A
RT
NUMBER
DESCRIPTION REM
A
RKS
/
A
LTERNATE PIL
A
TUS P
A
RT
NUMBER
11602 SEALANT RTV BLACK RTV 103
7471 THREAD SEALANT PRIMER LOCTITE 7471
569 THREAD SEALANT LOCTITE 569
RL-46H POE REFRIGERANT OIL ESTER

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DESCRIPTION AND OPERATION
2. SYSTEM DESCRIPTION AND OPERATION
2.1. General:
2.1.1. The air conditioning system installed on the Pilatus PC12 M19 Aircraft is not considered a
primary flight system. However, an air conditioning system does perform the important
function of providing passenger and flight crew comfort during aircraft movement on the
ground and while in flight. Aircraft air conditioning systems not only provide effective
passenger cooling, but must also maintain a high level of reliability to minimize aircraft
downtime due to unscheduled repairs.
2.1.2. In order to ensure component reliability and achieve a long service life for which the
system is designed, periodic inspection and preventive maintenance must be performed.
Failure to complete periodic inspections, service, or maintenance schedules may reduce
product life and potentially void manufacturer’s warranty.
2.1.3. Inspections, servicing, and/or maintenance schedules are presented in the following
sections. This will ensure component and/or system reliability and performance are
maintained when performed at the specified intervals.
WARNING: SERVICE TECHNICIANS ARE ADVISED TO OBSERVE STANDARD SAFETY
PRECAUTIONS, SUCH AS WEARING PERSONAL SAFETY GEAR, TO PREVENT INJURY WHILE
PERFORMING SERVICE TO THE UNIT. LIQUID REFRIGERANT CAN CAUSE FROSTBITE AND/OR
BLINDNESS.
WARNING: PROPER VENTILATION IS REQUIRED. KEEP REFRIGERANTS AND OILS AWAY FROM
OPEN FLAMES. REFRIGERANTS CAN PRODUCE POISONOUS GASSES IN THE PRESENCE OF A
FLAME. WORK IN A WELL VENTILATED AREA AND AVOID BREATHING REFRIGERANT /LUBRICANT
VAPOR MIST IF ACCIDENTAL DISCHARGE OCCURS.
WARNING: AVOID USE OF COMPRESSED AIR. DO NOT INTRODUCE COMPRESSED AIR OR
OXYGEN INTO AN AIR CONDITIONING SYSTEM OR REFRIGERANT CONTAINER. R-134A IN THE
PRESENCE OF AIR OR OXYGEN ABOVE ATMOSPHERIC PRESSURE MAY FORM A COMBUSTIBLE
MIXTURE.
2.1.4. Do not discharge R-134A refrigerant into the atmosphere. Although its ozone depletion
potential is zero, it can have an effect on global warming. In the United States recovery
and recycling are mandated by the Clean Air Act.

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2.1.5. Refrigerant recovery/recycling service equipment must be approved for use with R-134A
refrigerant. Recycling machines must be approved by Underwriters Laboratories (UL) and
meet SAE standard J2210 and SAE standard J2099 for refrigerant purity.
2.2. System Description and Operation:
2.2.1. The cabin cooling system installed in the Pilatus PC12 M19 Aircraft operates using a
closed vapor cycle concept using refrigerant R-134A as the heat absorption media. The
R-
134A air
conditioning system cools the aircraft in a similar manner as systems found in an
automobile or home. However, aircraft air conditioning systems contain components
which are designed to be light weight, compact, provide high performance, and provide the
ability to operate at extreme altitudes and ambient temperatures.
2.2.2. The concept of air conditioning a room, cabin or cockpit is straight forward. An example of
a system is shown in Figure 1 (refer to Schematic and Wiring Diagrams, Section
4).
Refrigerant is the media which absorbs and rejects the room or cabin heat. By continuous
recirculation of the warm cabin air, heat is absorbed in the evaporator module(s) and is
rejected to the outside through the system condenser. When the system is turned on, the
electric motor controller drives the R-134A compressor at a variable speed (dependent
upon current cooling requirements) which compresses the R-134A refrigerant gas to a
high pressure. The hot, high pressure gas then passes through the condenser coil where
it is cooled and condensed into a warm liquid at constant pressure. The warm liquid is
then routed into a receiver-dryer container where the liquid and any remaining gas are
separated and any moisture is absorbed. The warm, dry liquid is then directed to the
evaporator module expansion valve where the high pressure liquid is expanded to a low
pressure. The expansion process creates a super cool gas which passes through the
evaporator coil and absorbs heat from the warm cabin air passing over the coils. The
warm low pressure refrigerant then enters the R-134A compressor where the process
starts all over again. In addition to cooling the cabin air, a refrigerant type system also
removes a large percentage of the moisture in the air as well as removing dust and pollen
particles in the air. Thus, the system conditions the air as well as cooling it. As a safety
feature, the unit is also equipped with a binary pressure switch. This switch prevents the
unit from operating if the discharge pressure becomes excessively high. The switch also
prevents the unit from operating if the internal pressure is very low due to leakage or low
ambient temperatures.

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2.3. System Component Description and Operation:
The R-134A air conditioning system installed on the Pilatus PC12 M19 Aircraft uses the
following major system components:
 Direct Drive Compressor Module 1150950-3 (Supersedes 1150950-2)
 Evaporator Module Assembly 1150900-2 (L) / 1150910-2 (R)
 Condenser Coil Assembly w/Receiver Dryer 1150970-1
 Axial Condenser Fan 1250435-30
2.3.1. The direct drive compressor module has a rated cooling capacity of 17,000 BTUH when
operating with the other components in the Pilatus PC12 M19 Aircraft at an ambient
temperature of 95°F OAT. Under this condition, the current draw is limited to 105 AMPS at
28 VDC.
The Compressor Module Assembly is packaged to meet the aircraft installation
requirements and contains the following major components:
• Brushless Compressor Drive Motor
• Compressor Assembly
• Brushless Motor Controller
2.3.1.1. BRUSHLESS COMPRESSOR DRIVE MOTOR: The drive motor is attached to the
compressor shaft via a coupling allowing for direct speed control of the compressor.
2.3.1.2. COMPRESSOR ASSEMBLY: The compressor assembly is a 3d scroll type with a
displacement of 65 CC/Rev and is to only be used with R134a refrigerant and RL-46H
refrigerant oil.
2.3.1.3. BRUSHLESS MOTOR CONTROLLER: The motor controller is provided with the
following features to ensure safe operation.
 Run Signal – Reports Normal Operation
 Over Temperature Shutdown – Fail Signal
 Locked Rotor Detection – Fail Signal
 Hall Sensor Failure – Fail Signal
 Motor Field Winding Short – Fail Signal

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2.3.2. CONDENSER COIL ASSEMBLY: The condenser coil assembly is an aluminum micro-
channel type. The coil heat rejection is 24,650 BTUH based on a 104°F inlet temperature.
This assembly requires airflow of 900 CFM for proper operation. Coil face areas must be
unrestricted at all times or system performance degradation will occur. This unit is provided
with a high pressure relief valve that will activate a 550±50 psi and closes at 435 psi
minimum.
2.3.2.1. RECEIVER DRYER ASSEMBLY: The receiver-dryer assembly consists of
a
refrigerant container, Schrader valve, and a binary pressure switch. The receiver-dryer is
constructed of aluminum alloy and contains a standpipe, wire filter, and desiccant. The
Schrader valve located in the container inlet port allows for the binary pressure switch to be
removed without venting the system refrigerant charge.
2.3.2.2. BINARY PRESSURE SWITCH: The binary pressure switch performs two major
functions. The first function prevents the R-134A compressor from operating if the
system charge is lost or the ambient temperature is too low. The second function stops
the compressor from operating if the head pressure increases to an unsafe level. The
high pressure cutout is at 377±28.5 PSIG on rise and the low pressure cutout is at
28.5±2.85 PSIG falling.
2.3.3. EVAPORATOR MODULES: have a rated cooling capacity each of 8500 BTUH at an ambient air
temperature of 80° F (db), and 50% RH (relative humidity). The assembly provides an air flow up to
300 CFM (cubic feet per minute) in order to maintain these performance specifications.
The Evaporator Module Assembly is packaged to meet the aircraft installation requirements and
contains the following major components:
• Coil Assembly
• Blower Motor
• Blower Wheel
• Expansion Valve
2.3.3.1. COIL ASSEMBLY: The coil is constructed of aluminum tube and aluminum fins with
aluminum support brackets made of 6061-T6. Air flow must be unrestricted at all times
or the design point will not be met.

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2.3.3.2. BLOW ER MOTOR: The blower motor operates on 28 VDC with a rated current draw
of 18 AMPS Max. and has a design RPM of 2170 - 4800. The blower motor is a brushless
design with an integrated controller and was selected for its efficiency, excellent
controllability, long life and low vibration at high speeds. The motor has eight speeds,
lower speed designed for the heating recirculation requirement and higher speed designed
for maximum system cooling. It was designed for continuous operation.
2.3.3.3.
BLOW ER WHEEL: The blower wheel is the component that is used in concert with
the blower motor and provides for the movement of air. It is made of lightweight
aluminum that provides superior strength and durability.
2.3.3.4. EXPANSION VALVE: The expansion valve is an automatic thermostatic type. The
valve provides the proper refrigerant flow while maintaining constant return gas
superheat at all evaporator heat load conditions. Controlling the evaporator refrigerant
flow based on cooling demand prevents coil freeze up. This allows the system cooling
capacity to best meet transient aircraft heat load demands.

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TESTING AND FAULT ISOLATION
3. TESTING AND FAULT ISOLATION
3.1. General:
3.1.1 Testing and Fault Isolation of the R-134A Air Conditioning System may be necessary if the
system does not operate and/or perform in accordance with information contained herein.
Therefore it is necessary for the service personnel to diagnose the discrepancy by
troubleshooting the system and its components. To assist in this diagnoses, refer to table 3
(Trouble Shooting List)
3.2. System Leak Check Testing Procedure:
3.2.1. A leak check of the refrigerant plumbing system is important to ensure the system
maintains its charge to provide the designed performance and reduce damage to system
components. A periodic check of the system charge is required to determine if any loss of
refrigerant has occurred.
3.2.2. A system leak check is required any time one or more of the following conditions occur:
• New system plumbing installation
• Component replacement in the plumbing system
• Line or hose rupture
3.2.3. Special Tools and/or Equipment Required:
• Gaseous dry nitrogen, regulated source (0-500 psig)
• R-134A refrigerant charging manifold with gauges and hoses (low pressure gauge, 0-300
PSIG), (high pressure gauge, 0-600
PSIG)
• Leak check fluid (soap solution), (Spec MS-SNOOP-GAL)
• Assorted hand tools
• Hand and eye protection

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• Thread sealant primer, PN 7471 (Loctite)
• Thread sealant, PN 569 (Loctite)
• Hose adapter (1/2 in. male acme to ¼ in. female flare)
3.2.3.1. Remove, if required, all panels, doors, shrouds, etc., to gain access to
system/component being leak checked (refer to aircraft maintenance manual).
3.2.3.2. Remove, if required, any enclosures or access doors to expose all tubing, hoses,
fittings, etc. to the system components.
3.2.3.3. Verify all plumbing connections are tight.
3.2.3.4. Verify that power is removed from aircraft. If it is not practical to remove aircraft
power, technician must pull and collar applicable circuit breakers.
CAUTION: HIGH PRESSURE HOSE (RED) IS CONNECTED TO PORT MARKED “D” AND THE LOW
PRESSURE HOSE (BLUE) IS CONNECTED TO THE SERVICE PORT MARKED “S”. INCORRECT
CONNECTION COULD RESULT IN MANIFOLD DAMAGE AND/OR INCORRECT PRESSURE READINGS.
3.2.3.5. Remove service port caps from the A/C system. Service ports are located on the
compressor.
3.2.3.6. Close all manifold gauge valves and verify hose connections are tight.
3.2.3.7. Connect R-134A refrigerant charging manifold. R-134A service gauges contain quick-
connect fittings to minimize refrigerant loss. To install quick-connect, push on firmly until
locked (a "clicking" sound is heard). Hold the grip ring and pull to remove quick- connect
fittings.
3.2.3.8. Connect yellow charging hose to a regulated dry nitrogen source
NOTE: An adapter is required to connect yellow charging hose to the nitrogen source.
CAUTION: APPLY NITROGEN PRESSURE SLOWLY DURING THIS PROCEDURE OR DAMAGE TO
SYSTEM COULD RESULT.
CAUTION: DO NOT EXCEED 200 PSIG NITROGEN PRESSURE DURING PROCEDURE OR DAMAGE TO
EXPANSION VALVE WILL RESULT.
3.2.3.9. Slowly regulate nitrogen source to a pressure of 200 PSIG maximum.
3.2.3.10. Slowly open high pressure (red) manifold valve and allow system pressure to increase
gradually until a pressure of 200 psig is achieved. Allow time for system pressure to
equalize across expansion valve and note final system pressure.
CAUTION: DO NOT USE ANY LEAK DYE IN R-134A SYSTEM OR DAMAGE TO SYSTEM MAY RESULT.
CAUTION: DO NOT OVER TIGHTEN PLUMBING CONNECTIONS. STRIPPED THREADS OR CRACKED
FLARES MAY RESULT.

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3.2.3.11. Apply soapy leak check fluid to each fitting connection. If leaks are detected, attempt
to tighten fitting without over tightening. If leak cannot be corrected with tightening, system
must be evacuated (refer to Servicing, Section 13) and then fitting must be disconnected
and new thread sealant applied.
3.2.3.12. Using a wire brush and cleaning solvent, completely remove old thread sealant. Apply
a thin layer of thread sealant primer to fitting threads.
CAUTION: WHEN APPLYING THREAD SEALANT, TAKE EXTREME CARE TO KEEP SEALANT OFF
FIRST 2 OR 3 THREADS.
3.2.3.13. Apply Loctite thread sealant on all male fitting threads sparingly.
CAUTION: WHEN APPLYING R-134A OIL TO FLARE AND O-RING, TAKE EXTREME CARE TO KEEP OIL
AWAY FROM FITTING THREADS
3.2.3.14. Apply a light coating of R-134A refrigerant oil to flare and/or O-ring to prevent metal
galling or O-ring damage.
3.2.3.15. Tighten joints as required to stop leaks (refer to Table 1, Section 1.3 for torque
values).
CAUTION: VENT SYSTEM PRESSURE VERY SLOWLY TO ASSURE COMPRESSOR OIL IS NOT
VENTED WITH THE NITROGEN. DO NOT LET AIR ENTER THE SYSTEM.
3.2.3.16. After leak check is finished and system integrity is sound, turn off nitrogen source,
disconnect yellow charging hose from nitrogen source and slowly release nitrogen
pressure to zero.
3.2.3.17. Close manifold valve.
3.2.3.18. System is now ready for charging.
3.3. Fault Isolation (Trouble- Shooting):
3.5.1 The following list of system/component failures and/or abnormal operation and possible
solutions is only a partial listing of what may occur. The more informed service
personnel
are
in the operation of the system and its various components, the less time will be required
to diagnose failures. Use this trouble-shooting list as well as all information contained in this
manual, to aid in diagnosing system faults. Contact Enviro Systems customer service
for
any
items not listed in this trouble-shooting list.

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Table 4 Trouble-shooting
INDICATION PROB
A
BLE C
A
USE POSSIBLE SOLUTION
A. No System Power 1. Ground power not connected 1. Plug in ground power cart
2. Aircraft power switch off 2. Energize power switch
B. Power On But System Will
Not Operate
1. Air conditioner breaker off 1. Turn on
2. Air conditioner breaker failed 2. Replace
3. Air conditioner mode switch
failed
3. Replace
4. Failed pressure switch 4. Replace
5. Vented system 5. Pressure check, evacuate and
charge
6. Low ambient temperature 6. Normal cut out function
C. System Operates But Does
Not Cool
1. Low refrigerant charge 1.Charge as required
2. Overcharged system cutout 2. Reclaim refrigerant as required
3. Failed Compressor 3. Replace Compressor Drive
4. Failed Drive Motor 4. Replace Compressor Drive
5. Failed expansion valve(s) 5. Replace
6. Evaporator blower switch failed 6. Replace
7. Evaporator blower motor failed 7. Replace Evaporator Motor
8. Evaporator module air inlet
clogged
8. Remove Debris
9. Expansion valve inlet clogged 9. Remove Debris
10. Excessive moisture in system 10. Replace receiver dryer
11. Excessive oil in system 11. Drain excessive oil
D. Evaporator Noisy 1. Blower wheel out of round 1. Replace
2. Blower wheel hitting scroll 2. Align
3. Defective blower motor bearing 3. Replace Evaporator Motor
4. Loose mounting bracket 4. Tighten hardware
5. Air inlet clogged 5. Remove debris
E. Compressor Noisy 1. Defective compressor 1. Replace Compressor Drive
2. Loose mounting hardware 2. Tighten as required
3. Loose hose assembly 3. Secure as required
4. Loose fan blade 4. Replace Compressor Drive

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INDICATION PROB
A
BLE C
A
USE POSSIBLE SOLUTION
F. Compressor Assembly Will
Not Operate
1. Circuit Breaker failed or off 1. Energize or replace
2. System Over Charged/Over
Pressurized
2. Evacuate and Recharge to
correct amount.
3. Pressure switch failed 3. Replace
4. Drive motor failed 4. Replace Compressor Drive
5. Ground power cart not plugged
In
5. Connect as required
6. Low ambient temperature 6. Normal cutout
7. Low refrigerant charge 7. Charge system
8. Controller over temperature
switch o
p
en
8. Allow unit to cool. If switch still
o
p
en, re
p
lace Com
p
ressor Drive
G. No Evaporator Module Air
Flow
1. Circuit breaker off 1. Energize or replace
2. Mode switch failed 2. Replace
3. Fan speed switch failed 3. Replace
4. Seized motor 4. Replace
5. Blower wheel failed 5. Replace
6. Blocked air ducts 6. Remove debris
7. Aircraft power not on 7. Energize
8. Ground power not on 8. Energize
H. Evaporator Module Coil
Freezing
1. No air flow 1. Turn fan on
2. Expansion valve failed or
clogged
2. Remove debris or replace
I. Pressure Switch C
y
cles (High
Pressure Cutout)
1. System over charged 1. Reclaim refrigerant as required
2. Condenser coil inlet air
extremely hot
2. Normal condition
3. Condenser inlet clogged 3. Remove debris
4. Discharge line clogged or
kinked
4. Replace or straighten line
5. Excessively high ambient
temperature
5. Normal Condition

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PLUMBING DIAGRAM
4. SYSTEM PLUMBING DIAGRAM
4.1. R-134A Refrigerant Flow Schematic:
4.1.1. The following schematic shows an air conditioning system and its associated components as well
as the flow of the R-134A refrigerant.
Figure 1 VCS Refrigerant Schematic