AirComm Corporation Cessna 182T T182T Maintenance Manual
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Products, Inc. Maintenance Manual with Illustrated Parts Catalog CR-182-10 Introduction Page xi October 15, 2009 3. GLOSSARY Nonstandard abbreviations and symbols used in the Maintenance Manual are described below. A/C - Air-conditioning A/R - As Required Assy - Assembly Comm. Avail. - Commercially Available Evap - Evaporator Gnd - Ground GPU - Ground Power Unit SW - Switch VDC - Volts Direct Current
Products, Inc. Maintenance Manual with Illustrated Parts Catalog CR-182-10 21-50-00 Page 1 April 5, 2002 AIR-CONDITIONING SYSTEM SYSTEM DESCRIPTION 1. AIR-CONDITIONING SYSTEM DESCRIPTION The Keith Products vapor cycle air-conditioning system uses liquid refrigerant R134a to cool the aircraft cabin. The major components for the R134a air- conditioning system consist of a compressor, condenser, receiver/drier, expansion valve, and evaporator. The starter ring-gear pulley turns the compressor via a belt. Figure 1 shows an operational schematic of the air-conditioning system. The gas in the suction hose is pumped into the discharge hose and through the refrigerant system by the compressor. The compressor takes the low- temperature, low-pressure gas and compresses it to a high-temperature, high- pressure gas. After the high-temperature, high-pressure gas leaves the compressor it enters the condenser. A 28 VDC blower forces air from the left hand side of the aircraft in the inlet duct and through the condenser. The air exits the condenser and leaves the condenser through the exhaust duct on the right hand side of the tailcone. This air cools the high-temperature, high-pressure gas as much as 100ºF. The gas is cooled until it condenses to a medium-temperature, high-pressure liquid. After the medium-temperature, high-pressure liquid leaves the condenser it enters the receiver/drier. The receiver/drier stores liquid refrigerant and filters any moisture out of the refrigerant. After the medium-temperature, high-pressure liquid leaves the receiver/drier it enters the expansion valve. The expansion valve allows the medium-temperature, high-pressure liquid to expand to a low-temperature, low-pressure spray of liquid. After the low-temperature, low-pressure spray of liquid leaves the expansion valve it enters the evaporator. A 28 VDC blower forces air from the cabin through the evaporator. Since the refrigerant in the evaporator can be as cold as 30ºF, the air from the cockpit causes the low-temperature, low-pressure liquid spray to boil and then evaporate. This low-temperature, low-pressure gas passes through the suction hose into the compressor. The refrigerant cycle continues, cooling the aircraft cabin. Air from the cabin is cooled as it passes through the evaporator and comes into contact with the refrigerant. Since the air is cooled, moisture from the air condenses in the evaporator and liquid water is formed. The water then drains overboard through the floor of the aircraft.
Products, Inc. Maintenance Manual with Illustrated Parts Catalog CR-182-10 21-50-00 Page 2 April 5, 2002 Figure 1. Air-conditioning Vapor Cycle System
Products, Inc. Maintenance Manual with Illustrated Parts Catalog CR-182-10 21-50-00 Page 3 April 5, 2002 2. SYSTEM OPERATION The air-conditioning system is operated with the engine operating and power supplied to the aircraft electrical system. To operate the system proceed as follows: 1) Turn on air-conditioning system by placing left hand control switch in the AIR COND position. 2) For maximum cooling, place the FAN control knob in the HI position, place the CABIN COOLING control knob in the MAX position, and close cabin and baggage doors. 3) Turn off air-conditioning system by placing left hand control switch in the OFF position. 4) Airflow may be varied infinitely by rotating the FAN control knob between the LO and HI positions. 5) Cabin air cooling may be varied by rotating the CABIN COOLING control knob between the MIN and MAX positions. 6) Cabin air may be re-circulated without the air-conditioning system operating by placing the left hand control switch in the FAN position.
Products, Inc. Maintenance Manual with Illustrated Parts Catalog CR-182-10 21-50-00 Page 101 April 5, 2002 AIR-CONDITIONING SYSTEM TROUBLESHOOTING 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 of the air-conditioning system varies with ambient temperature and humidity. The information below presents possible air-conditioning system problems and solutions. CAUTION: Do not operate air-conditioning system with condenser air outlet blocked. 2. AIR-CONDITIONING SYSTEM DIAGNOSIS CHART The following pages show a procedure for diagnosing air-conditioning system problems that will expedite the troubleshooting process.
21-50-00 Page 102 April 5, 2002 INSUFFICIENT COOLING SUCTION PRESSURE IS HIGH EXPANSIO0N VALVE IS OPEN EXCESSIVELY. CHECK SENSING BULB INSTALLATION. IF SECURE & WELL INSULATED, THEN REPLACE EXPANSION VALVE. IF NOT, THEN SECURE AND PROPERLY INSULATE AND RETEST. PLUMBING AT RECEIVER/DRIER OUTLET HAS LOW TEMPERATURE. RECEIVER/DRIER IS RESTRICTED. REPLACE RECEIVER/DRIER. BUBBLES IN SIGHT GLASS CHECK REFRIGERATION LINE FOR GAS LEAKS, AND REPAIR LEAKS IF ANY. CHARGE REFRIGERANT TO CORRECT LEVEL. IN CASE OF TOO MANY LEAKS, STOP COMPRESSOR, DISCHARGE THE SYSTEM, EVACUATE AND RECHARGE THE SYSTEM. AS NECESSARY, REPLACE RECEIVER/DRIER. AIR IN SYSTEM MAY CAUSE BUBBLES IN SIGHT GLASS. DISCHARGE PRESSURE IS HIGH CONDENSER AIR TEMP, TOO HIGH SYSTEM PRESSURES ARE ABNORMAL TEMPERATURE OF DISCHARGE AIR IS ABNORMAL, BUT SYSTEM PRESSURE IS NORMAL. OPERATE AIR-CONDITIONING SYSTEM. WITH MANIFOLD GAUGE, CHECK SYSTEM SUCTION AND DISCHARGE PRESSURES. MEASURE TEMPERATURE OF EVAPORATOR AND CONDENSER DISCHARGE AIR. NO BUBBLES IN SIGHT GLASS 1. OVERCHARGE OF REFRIGERANT DISCHARGE SOME OF REFRIGERANT TO CORRECT LEVEL 2. AIR IS MIXED IN. DISCHARGE SYSTEM, AND REPLACE RECEIVER/DRIER. EVACUATE AND RECHARGE SYSTEM 3. CONDENSER’S FINS ARE DENTED OR CLOGGED WITH DUST. CLEAN PER SERVICING INSTRUCTIONS SUCTION PRESSURE IS LOW FINS AND TUBES OF EVAPORATOR HAVE SOME DENTS. REPLACE OR REPAIR EXPANSION VALVE IS TOO RESTRICTIVE OR GAS LEAKAGE FROM SENSING ELEMENT. REPLACE EXPANSION VALVE. EVAPORATOR AIR TEMP TOO HIGH CLEAN OR REPLACE CONDENSER CLEAN OR REPLACE EVAPORATOR SUCTION PRESSURE IS HIGH WHILE DISCHARGE IS LOW REPAIR OR REPLACE COMPRESSOR FIGURE 2: AIR-CONDITIONING SYSTEM DIAGNOSIS CHART
Products, Inc. Maintenance Manual with Illustrated Parts Catalog CR-182-10 21-50-00 Page 103 April 5, 2002 3. AIR-CONDITIONING SYSTEM TROUBLESHOOTING CONDITION SERVICE PRESSURE GAUGE READING PROBABLE CAUSE CORRECTIVE ACTION INSUFFICIENT REFRIGERANT CHARGE Insufficient cooling. Bubbles appear in sight glass. 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 recharge system. ALMOST NO REFRIGERANT No cooling action. A lot of bubbles or something like mist appears in sight glass. SUCTION PRESSURE: much below normal DISCHARGE PRESSURE: much below normal Serious refrigerant leak. Stop compressor immediately. 1. Leak test. 2. Discharge system. 3. Repair Leak(s). 4. Replace receiver/drier, if necessary. 5. Check oil level. 6. Evacuate and recharge system. FAULTY EXPANSION VALVE a) Slight cooling. Sweating or frosted expansion valve outlet. b) Insufficient cooling. Sweated suction line. c) No cooling. Sweating or frosted suction line. a) SUCTION PRESSURE: below normal DISCHARGE PRESSURE: below normal b) SUCTION PRESSURE: above normal DISCHARGE PRESSURE: above normal c) SUCTION PRESSURE: above normal DISCHARGE PRESSURE: below normal a) Expansion valve restricts refrigerant. Or, expansion valve is clogged. Or, expansion valve is inoperative. Or, valve stuck closed. Thermal bulb has lost charge. b) Expansion valve allows too much refrigerant through evaporator. Sensing bulb on suction line not well insulated or properly attached to line. c) Faulty expansion valve. a) Replace expansion valve. b) 1. Check valve for operation. If suction side does not show a pressure decrease, replace valve. 2. Check security and insulation on sensing bulb. c) 1. Discharge system. 2. Replace valve. 3. Evacuate and replace system.
Products, Inc. Maintenance Manual with Illustrated Parts Catalog CR-182-10 21-50-00 Page 104 April 5, 2002 CONDITION SERVICE PRESSURE GAUGE READING PROBABLE CAUSE CORRECTIVE ACTION AIR IN SYSTEM Insufficient cooling. Sight glass 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 suction side may show vacuum pressure reading. During this condition, discharge air will be warm. As warning of this, reading shows approx. 6 psi oscillation. SUCTION PRESSURE: below normal DISCHARGE PRESSURE: above normal Drier is saturated with moisture. Moisture has frozen at expansion valve. Refrigerant flow is restricted. 1. Discharge system. 2. Replace receiver/ drier (twice if necessary). 3. Evacuate system completely. (Repeat 30 minute evacuating three times.) 4. Recharge system. FAULTY CONDENSER Insufficient cooling. Bubbles appear in sight glass of drier. Suction line is very hot. SUCTION PRESSURE: above normal DISCHARGE PRESSURE: above normal Condenser air or refrigerant flow is restricted. Check condenser for dirt accumulation or bent fins. Clean/ replace as necessary. Check for refrigerant overcharge. If pressure remains high in spite of all above actions taken, remove and inspect the condenser for possible oil clogging. HIGH PRESSURE LINE BLOCKED Insufficient cooling. Frosted high pressure liquid line. SUCTION PRESSURE: much below normal DISCHARGE PRESSURE: much above normal Drier clogged, or restriction in high pressure line. 1. Discharge system. 2. Replace receiver/drier. 3. Evacuate and charge system
Products, Inc. Maintenance Manual with Illustrated Parts Catalog CR-182-10 21-50-00 Page 105 April 5, 2002 CONDITION SERVICE PRESSURE GAUGE READING PROBABLE CAUSE CORRECTIVE ACTION FAULTY COMPRESSOR a) Insufficient cooling. b) Insufficient cooling. c) Rough running. a) SUCTION PRESSURE: much below normal DISCHARGE PRESSURE: much below normal b) SUCTION PRESSURE: much above normal DISCHARGE PRESSURE: much below normal a) Internal problem in compressor, or damaged gasket and valve. b) Internal problem with compressor body. c) Internal problem with compressor body. 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. WATER BEING BLOWN OUT OF EVAPORATOR SUCTION PRESSURE: normal DISCHARGE PRESSURE: normal Blocked evaporator drain. Check evaporator drain for downhill routing and repair any kinks or blockage in drain tubing.
Products, Inc. CR-182-10 System Service Manual 21-50-00 Page 201 April 5, 2002 AIR-CONDITIONING SYSTEM MAINTENANCE PROCEDURES A. General The following procedures are used to perform typical maintenance on the air- conditioning system plumbing. Procedures are provided for making connections to components, and replacing the expansion valve. Keith Products air- conditioning systems use swaged hose fittings with o-ring type connections. B. Tools and Equipment Designation Ref. No. Qty Remarks Polyolester Oil Comm. Avail. A/R Viscosity ISO 68 Sealant ES49000-1 A/R None C. Connection to Components - O-Ring Replacement 1. Place the appropriate o-ring over the tube O end of the fitting. 2. Lubricate o-ring with polyolester oil viscosity ISO 68 or ES49000-1 sealant prior to assembly. 3. Apply sealant to all fitting mating surfaces prior to assembly. D. Expansion Valve Removal and Installation The following procedure is used to remove or install the air-conditioning system expansion valve, located on the inlet side of the evaporator coil. 1. Discharge system in accordance with instructions included in this manual. 2. Disconnect and cap the liquid hose from the expansion valve inlet. 3. Remove the insulation covering the thermal sense bulb on the suction tubing. 4. Cut the tie wraps binding the sense bulb to the suction tubing. 5. Disconnect the fitting that connects the expansion valve to the coil, and remove the expansion valve. 6. Discard the old expansion valve and o-ring. 7. Install new ES26104-1 expansion valve and ES49011 –2 o-ring. 8. Lubricate o-ring with polyolester oil viscosity grade ISO 68 or apply ES49000-1 sealant to fitting mating surfaces prior to assembly. 9. Install the thermal sense bulb such that it makes contact with the suction tube along its entire length with two or more cable ties as shown in Figure 3. 10. Insulate the bulb thoroughly with insulation to suction tubing. NOTE: Always utilize two wrenches as not to twist or bend the soft copper lines.