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AirComm Corporation Cessna 414 421 Air Conditioning System Service Manual R134a
AirComm Corporation Cessna 414 421 Air Conditioning System Service Manual R134a
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TR-134 Revision J September 13, 2013 Page 24 CONDITION SERVICE PRESSURE GAUGE READING PROBABLE CAUSE CORRECTIVE ACTION FAULTY COMPRESSOR Insufficient cooling. SUCTION PRESSURE: much above normal DISCHARGE PRESSURE: much below normal Internal problem in compressor, or damaged gasket and valve. 1. Discharge system. 2. Remove and check compressor. 3. Repair or replace compressor. 4. Check oil level. 5. Replace receiver drier. 6. Evacuate and charge system. TOO MUCH OIL IN SYSTEM (Excessive) Insufficient cooling. SUCTION PRESSURE: above normal DISCHARGE PRESSURE: above normal Too much oil circulates with refrigerant, causing the cooling capacity of the system to be reduced. Refer to Oil Level Check for correcting oil level.
TR-134 Revision J September 13, 2013 Page 25 5.4 Compressor Troubleshooting A. General The following procedures are used for troubleshooting the compressor. B. Tools and Equipment Designation Ref. No. Qty Remarks Service Pressure Gauge Comm. Avail. 1 None DC Power Supply A/R None C. Compressor Troubleshooting Procedures With the air conditioning system operating, do any of the following conditions occur: NOTE: Always attach a service gauge set to the system prior to trouble shooting, to insure proper refrigerant charge is present. Trouble Probable Cause Correction 1. Unusually high suction pressure with low discharge pressure. (a) Internal problem with compressor body. (b) Faulty Expansion valve (a) Replace compressor. (b) Replace expansion valve 2. Unusually low suction and discharge pressure. System or compressor leak. Repair leak or replace compressor 3. High compressor discharge pressure. (a) Air exhaust duct collapsed or restricted. (b) Refrigerant overcharge. (a) Inspect/replace exhaust duct. (b) Discharge refrigerant until only occasional bubble are present in sight glass (if so equipped) or until pressures are with range (ref Table A.1).
TR-134 Revision J September 13, 2013 Page 26 4. Rough running. Internal compressor problem. Replace compressor. 6.0 CHECKS 6.1 General The following procedures are used to perform typical maintenance checks for air conditioning system refrigerant leaks, refrigerant charge and compressor oil level. CAUTION: Do not operate air conditioning system with condenser air outlet blocked. A. Tools and Equipment Designation Ref. No. Qty Remarks Service Pressure Gage Comm. Avail. 1 None Oil Dipstick Make from metal wire. 1 See Fig. 3. Electronic Leak Detector Comm. Avail. A/R Type H-10G Polyolester Oil Comm. Avail. A/R Viscosity ISO 68 6.2 Refrigerant Level Check A. Connect service cart with gages to the system B. Select air conditioning system to ON. C. Set the temperature selector (if so equipped) to the full cold position. D. Set the blower speed to the maximum position. E. Run system for five (5) minutes minimum. F. Check that pressures are within range per Table A.1. Add or recover refrigerant as required until pressures are within range. If so equipped, a less accurate method is to check the sight glass for presence of bubbles. Add refrigerant until bubbles disappear. NOTE: Accurate readings are difficult to obtain when ambient temperatures are below 65F. Always re-check refrigerant level when ambient temperature is above 65F for proper level.
TR-134 Revision J September 13, 2013 Page 27 6.3 Refrigerant System Leakage Check A. The system leakage check is to be performed in an area with an ambient temperature of 65F or above. B. Install service pressure gage to low and high pressure R-134a service valves. C. Check for system pressure of approximately 64 psig or above. The low pressure gage may be used to check system pressure. If system pressure is below 64 psig, a small amount of refrigerant R-134a may be added to obtain the required pressure. D. On systems that have not been operated for 2 weeks or longer, operate the system for a minimum of 15 minutes. This will lubricate the compressor shaft seal and ensure a more accurate leakage check of the shaft seal. E. With the system off, and using a type H-10G electronic leak detector or equivalent, check all connections, compressor shaft seal, and fabricated components for leakage. No leakage is acceptable 6.4 Compressor Oil Level Check NOTE: It is not necessary to check the compressor oil level during routine maintenance. It only needs to be checked when a system component is replaced or when incorrect oil level is suspected. Only polyolester oil viscosity grade ISO 68 should be used. A. Operate air conditioning system for 10 minutes. This will collect as much oil as possible in the compressor. B. Perform flushing procedure.
TR-134 Revision J September 13, 2013 Page A-1 APPENDIX A
TR-134 Revision J September 13, 2013 Page A-2 A-1.0 CHARGE PRESSURES A-1.1 Normal Range OAT 65 25 35 135 155 70 35 40 145 160 75 35 45 150 170 80 40 50 175 210 85 45 55 225 250 90 45 55 250 270 95 50 55 275 300 100 50 55 315 325 105 50 55 330 335 110 50 55 340 345Normal range for pressuresSuction (psig) Discharge (psig) Table A.1 A-1.2 Interpreting Readings Suction Discharge Low Low Low Hi gh Hi gh Low Hi gh Hi ghNeeds service. Possible faulty compre ssor. Overcharged. Recover refrigerant until pressures are in range. Interpreting Pressure Re adingsAction Required Add re fri ge rant until pressures are in range. Need service. Possible expansion valve blockage Table A.2