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AIR CONDITIONING SYSTEM DIAGNOSIS

AIR CONDITIONING SYSTEM DIAGNOSIS. CHAP 4 AND 7. OBJECTIVES. Diagnose six system malfunctions by gauge readings. Identify the low and high side of the air conditioning system. Read and understand temperature-pressure charts. Discuss temperature-pressure relationships. OBJECTIVES.

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AIR CONDITIONING SYSTEM DIAGNOSIS

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  1. AIR CONDITIONING SYSTEM DIAGNOSIS CHAP 4 AND 7

  2. OBJECTIVES • Diagnose six system malfunctions by gauge readings. • Identify the low and high side of the air conditioning system. • Read and understand temperature-pressure charts. • Discuss temperature-pressure relationships.

  3. OBJECTIVES • Identify differences between CFC-12 and HFC-134a systems. • Identify differences between thermostatic expansion valve (TXV) and fixed orifice tube (FOT) systems. • Understand the proper handling of refrigerants and refrigeration oil.

  4. INTRODUCTION • Figure 4-1, (Pg 68C) shows the dividing line between low and high sides. • Low side gauge is a compound gauge. • There is a direct relationship between pressure and temperature. • Air temp flowing through evaporator will be a few degrees warmer than the refrigerant.

  5. ACSYSTEM Low side Expansion Valve High side

  6. CHECK THESE FIRST • BELT TENSION • CLUTCH OPERATION • RADIATOR/CONDENSER FAN OPERATION • PROPER FLOW FROM DUCTS • SIGHT GLASS IN R-12 SYSTEMS • REFRIGERANT CHARGE • SUCTION LINE • LIQUID LINE • SERVICE VALVES • LINES, HOSES, CONNECTIONS

  7. SYSTEM DIAGNOSIS • Knowing the ambient air temperature. • Determine normal HIGH side pressure. (Pressure chart page 69C) • There are seven conditions for A/C systems. • 1 normal condition. • 6 conditions that indicate a malfunction.

  8. NORMAL OPERATIONAmbient Temperature: 90 degrees Fahrenheit • Low-side gauge: Normal pressure • CFC-12: 32-33 PSI • HFC-134a: 30-31 PSI • High-side gauge: Normal pressure • CFC-12: 185-190 PSI • HFC-134a: 204-210 PSI

  9. PLATE 1 • Normal expansion valve system

  10. PLATE 9 • Normal orifice tube system

  11. INSUFFICIENT COOLING #2 • Low side Gauge: Low Pressure CFC-12 15 psig HFC-134a 12 psig • High Side Gauge: Normal Pressure CFC-12 190 psig HFC-134a 208 psig • Possible Causes: Thermostat (icing) Low side restriction Moisture in system pg 70C

  12. CONDITION #2

  13. INSUFFICIENT OR NO COOLING #3 page 71C • Low Side Gauge: Low or Very low Pressure • CFC-12: 18 psig • HFC-134a : 15 psig • High Side Gauge: Low Pressure • CFC-12: 130-135 psig • HFC-134a: 139-144 psig • Possible causes: Clogged TXV inlet screen, bad valve, Moisture in system

  14. Pg 72C INSUFFICIENT OR NO COOLING #4 • Low side gauge: Low Pressure • CFC-12: 22 psig • HFC-134a: 20 psig • High side gauge: High to extremely High • CFC-12: 250 psig • HFC-134a 281 psig • Causes: Restriction in High Side • Temperature change present at restriction

  15. Pg 73C INSUFFICIENT OR NO COOLING #5 • Low side: High Pressure • CFC-12: 44 psig • HFC-134a: 43 psig • High side: Low Pressure • CFC-12: 140 psig • HFC-134a: 150 psig • Causes: Bad Clutch, Bad compressor • (compressor not turning normally mech... or electrical)

  16. INSUFFICIENT COOLING #6 pg 74C • Low Side: High Pressure • CFC-12: 40 psig • HFC-1334a 38 psig • High Side: Normal Pressure • CFC-12: 170 psig • HFC-134a: 184 psig • Causes: Expansion Valve stuck open

  17. Pg 75C INSUFFICIENT OR NO COOLING #7 • Low Side: High Pressure • CFC-12: 42 psig • HFC-134a: 37 psig • High Side: High to extremely High • CFC-12: 235 psig • HFC-134a: 263 psig • Causes: Air in system, Overcharge, overcharge of oil, Clogged condenser, Non op Fans, Engine overheating

  18. R-22 for LEAK TESTING • R-12 = 50psi • R-22 = 100psi • Do NOT mix refrigerants • R-22 is NOT a replacement for R-12 • Small amounts of R-22 used in leak testing can be vented to atmosphere. • Can Dye Test if needed (pg 197L) page 82C

  19. SERVICING TIPS • A/C oil level should be checked each time the system is drained. • Keep the cap on oil container. • Refrigerant oil is hygroscopic. • Moisture is damaging to A/C system. • Add oil removed from system if a major loss has occurred.

  20. PREVENTIVE MAINTENANCE • Inspect electrical system for A/C • Inspect Blower motor for abnormal noises, leaves in ducts, etc. • Check Voltages • Check Compressor Clutch operation • Check Belts and A/C Hoses • A/C Function Check page 88

  21. Your so Cool, Later Babe!!!

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