AirComm Corporation Cessna 414 421 Air Conditioning System Service Manual R134a

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4.3  Plumbing System Maintenance Procedures 
 
A. General 
 
The following procedures are used to perform typical maintenance on the air 
conditioning system plumbing.  Procedures are provided for hose or fitting 
replacement.  New ACC air conditioning systems use swaged hose fittings.  
Some systems that have been converted from R12 to R134a refrigerant use Barb 
Lok hose fittings.  Fittings are either o-ring type or use flared connections....

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D.  Hose or Fitting Replacement (Barb-Lok Hose Fittings) 
 
NOTE:  If it is found that a hose or fitting has a leak, it will be necessary to 
replace the entire hose assembly.  Follow the Hose Barb-Lok Instruction below: 
 
1.  Hose should only be cut with a sharp knife.  (Note:  Use of serrated 
blades or saws to cut hose will leave particles that can contaminate system.) 
2.  Slide the Barb-Lok socket onto the hose fitting with the round end...

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4.4  Coil Cleaning Maintenance Procedures 
 
A. General 
 
The following procedure is used for cleaning either evaporator or condenser coil. 
B. Tools and Equipment 
 
 
Designation  
Ref. No.  
Qty  
Remarks 
 
 
Vacuum Cleaner  
Comm. Avail.  
1  
None 
 
Coil Cleaner  
Comm. Avail.  
A/R  
Non-acid based 
 
C.  Coil Cleaning Procedure 
1.  Use vacuum cleaner to remove large debris from upstream and 
downstream coil faces. 
2.  Spray coil...

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4.5  Expansion Valve Removal and Installation 
 
A. General 
 
The following procedure is used to remove or install the air conditioning system 
expansion valve. 
 
B. Tools and Equipment 
 
Designation 
  
Ref. No.  
Qty  
Remarks 
 
Sealant  
ES49000-1  
A/R  
None 
 
Polyolester Oil  
Comm. Avail.  
A/R  
Viscosity ISO 68 
 
C. Expansion Valve Replacement 
 
1.  Discharge system in accordance with Refrigerant Servicing section. 
2.  Disconnect...

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Figure 4-1 
 
Figure 4-2 
 
Figure 4-3 
  

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4.6  Compressor Maintenance Procedures 
 
A. General 
 
The following procedure is used whenever the compressor is replaced or 
contamination is suspected. 
 
B. Tools and Equipment 
Designation Ref. No. Qty Remarks 
None - - None 
 
C. Compressor Replacement 
 
Flush system and replace compressor per the Refrigerant Servicing section.  

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5.0 TROUBLESHOOTING 
 
5.1 General 
 
The procedures below present troubleshooting charts for the air conditioning 
system and the compressor.  A diagnoses chart is presented for insufficient air 
conditioning system cooling.  The performance characteristics of an aircrafts 
particular system are dependent upon the design parameters of the systems 
components.  The performance of any one particular system varies with ambient 
temperature and...

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Figure 3.  Air Conditioning System Diagnosis Chart  

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5.3  Air Conditioning System Troubleshooting 
 
 
 CONDITION  
SERVICE PRESSURE 
GAUGE READING  
 PROBABLE CAUSE  
CORRECTIVE ACTION 
INSUFFICIENT 
REFRIGERANT 
CHARGE 
 
Insufficient cooling.  
Bubbles appear in sight 
glass (if so equipped).   SUCTION  
PRESSURE:  below 
normal 
 
DISCHARGE 
PRESSURE:  below 
normal Refrigerant is low, or leaking 
a little. 1.  Leak test. 
2.  Repair leak. 
3.  Charge system. 
 
Evacuate as necessary 
and...

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 CONDITION  
SERVICE PRESSURE 
GAUGE READING  
 PROBABLE CAUSE  
CORRECTIVE ACTION 
AIR IN SYSTEM 
 
Insufficient cooling.  
 
Sight glass (if so 
equipped) shows 
occasional bubbles.   SUCTION  
PRESSURE:  above 
normal 
 
DISCHARGE 
PRESSURE:  above 
normal Air mixed with refrigerant in 
system. 1. Discharge system. 
2. Replace receiver drier. 
3. Evacuate and charge 
system. 
 
MOISTURE IN SYSTEM 
 
After operation for a 
while, pressure on...