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 INTRODUCTIONFigure 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.
6 CHECK THESE FIRST BELT TENSION CLUTCH OPERATION RADIATOR/CONDENSER FAN OPERATIONPROPER FLOW FROM DUCTSSIGHT GLASS IN R-12 SYSTEMSREFRIGERANT CHARGESUCTION LINELIQUID LINESERVICE VALVESLINES, 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 OPERATION Ambient Temperature: 90 degrees Fahrenheit Low-side gauge: Normal pressureCFC-12: PSIHFC-134a: PSIHigh-side gauge: Normal pressureCFC-12: PSIHFC-134a: PSI
13 INSUFFICIENT OR NO COOLING #3 page 71CLow Side Gauge: Low or Very low PressureCFC-12: psigHFC-134a : 15 psigHigh Side Gauge: Low PressureCFC-12: psigHFC-134a: psigPossible causes: Clogged TXV inlet screen, bad valve, Moisture in system
14 INSUFFICIENT OR NO COOLING #4 Pg 72CINSUFFICIENT OR NO COOLING #4Low side gauge: Low PressureCFC-12: psigHFC-134a: 20 psigHigh side gauge: High to extremely HighCFC-12: 250 psigHFC-134a 281 psigCauses: Restriction in High SideTemperature change present at restriction
15 INSUFFICIENT OR NO COOLING #5 Pg 73CINSUFFICIENT OR NO COOLING #5Low side: High PressureCFC-12: psigHFC-134a: 43 psigHigh side: Low PressureCFC-12: psigHFC-134a: 150 psigCauses: Bad Clutch, Bad compressor(compressor not turning normally mech... or electrical)
16 INSUFFICIENT COOLING #6 pg 74CLow Side: High PressureCFC-12: 40 psigHFC-1334a 38 psigHigh Side: Normal PressureCFC-12: psigHFC-134a: psigCauses: Expansion Valve stuck open
17 INSUFFICIENT OR NO COOLING #7 Pg 75CINSUFFICIENT OR NO COOLING #7Low Side: High PressureCFC-12: psigHFC-134a: 37 psigHigh Side: High to extremely HighCFC-12: psigHFC-134a: 263 psigCauses: 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 refrigerantsR-22 is NOT a replacement for R-12Small amounts of R-22 used in leak testing can be vented to atmosphere.Can Dye Test if needed (pg 197L)page 82C
19 SERVICING TIPSA/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/CInspect Blower motor for abnormal noises, leaves in ducts, etc.Check VoltagesCheck Compressor Clutch operationCheck Belts and A/C HosesA/C Function Checkpage 88