Presentation on theme: "CBC AUTO AIR CONDITIONING SYSTEM DIAGNOSIS CHAP 4 AND 7."— Presentation transcript:
CBC AUTO AIR CONDITIONING SYSTEM DIAGNOSIS CHAP 4 AND 7
CBC AUTO OBJECTIVES l Diagnose six system malfunctions by gauge readings. l Identify the low and high side of the air conditioning system. l Read and understand temperature-pressure charts. l Discuss temperature-pressure relationships.
CBC AUTO OBJECTIVES l Identify differences between CFC-12 and HFC-134a systems. l Identify differences between thermostatic expansion valve (TXV) and fixed orifice tube (FOT) systems. l Understand the proper handling of refrigerants and refrigeration oil.
CBC AUTO INTRODUCTION l Figure 4-1, (Pg 68C) shows the dividing line between low and high sides. l Low side gauge is a compound gauge. l There is a direct relationship between pressure and temperature. l Air temp flowing through evaporator will be a few degrees warmer than the refrigerant.
CBC AUTO ACSYSTEMACSYSTEM Low side High side Expansion Valve
CBC AUTO CHECK THESE FIRST l BELT TENSION l CLUTCH OPERATION l RADIATOR/CONDENSER FAN OPERATION l PROPER FLOW FROM DUCTS l SIGHT GLASS IN R-12 SYSTEMS l REFRIGERANT CHARGE l SUCTION LINE l LIQUID LINE l SERVICE VALVES l LINES, HOSES, CONNECTIONS
CBC AUTO SYSTEM DIAGNOSIS l Knowing the ambient air temperature. l Determine normal HIGH side pressure. (Pressure chart page 69C) l There are seven conditions for A/C systems. l 1 normal condition. l 6 conditions that indicate a malfunction.
CBC AUTO NORMAL OPERATION Ambient Temperature: 90 degrees Fahrenheit l Low-side gauge: Normal pressure – CFC-12: PSI – HFC-134a: PSI l High-side gauge: Normal pressure – CFC-12: PSI – HFC-134a: PSI
CBC AUTO PLATE 1 l Normal expansion valve system
CBC AUTO PLATE 9 l Normal orifice tube system
CBC AUTO INSUFFICIENT COOLING #2 l Low side Gauge: Low Pressure CFC psig HFC-134a 12 psig l High Side Gauge: Normal Pressure CFC psig HFC-134a 208 psig l Possible Causes: Thermostat (icing) Low side restriction Moisture in system pg 70C
CBC AUTO l CONDITION #2
CBC AUTO INSUFFICIENT OR NO COOLING #3 l Low Side Gauge: Low or Very low Pressure – CFC-12: 18 psig – HFC-134a : 15 psig l High Side Gauge: Low Pressure – CFC-12: psig – HFC-134a: psig l Possible causes: Clogged TXV inlet screen,bad valve, Moisture in system page 71C
CBC AUTO INSUFFICIENT OR NO COOLING #4 l Low side gauge: Low Pressure – CFC-12: 22 psig – HFC-134a: 20 psig l High side gauge: High to extremely High – CFC-12: 250 psig – HFC-134a 281 psig l Causes: Restriction in High Side – Temperature change present at restriction Pg 72C
CBC AUTO INSUFFICIENT OR NO COOLING #5 l Low side: High Pressure – CFC-12: 44 psig – HFC-134a: 43 psig l High side: Low Pressure – CFC-12: 140 psig – HFC-134a: 150 psig l Causes: Bad Clutch, Bad compressor – (compressor not turning normally mech... or electrical) Pg 73C
CBC AUTO INSUFFICIENT COOLING #6 l Low Side: High Pressure – CFC-12: 40 psig – HFC-1334a 38 psig l High Side: Normal Pressure – CFC-12: 170 psig – HFC-134a: 184 psig l Causes: Expansion Valve stuck open pg 74C
CBC AUTO INSUFFICIENT OR NO COOLING #7 l Low Side: High Pressure – CFC-12: 42 psig – HFC-134a: 37 psig l High Side: High to extremely High – CFC-12: 235 psig – HFC-134a: 263 psig l Causes: Air in system, Overcharge, overcharge of oil, Clogged condenser, Non op Fans, Engine overheating Pg 75C
CBC AUTO R-22 for LEAK TESTING l R-12 = 50psi l R-22 = 100psi l Do NOT mix refrigerants l R-22 is NOT a replacement for R-12 l Small amounts of R-22 used in leak testing can be vented to atmosphere. l Can Dye Test if needed (pg 197L) page 82C
CBC AUTO SERVICING TIPS l A/C oil level should be checked each time the system is drained. l Keep the cap on oil container. l Refrigerant oil is hygroscopic. l Moisture is damaging to A/C system. l Add oil removed from system if a major loss has occurred.
CBC AUTO PREVENTIVE MAINTENANCE l Inspect electrical system for A/C l Inspect Blower motor for abnormal noises, leaves in ducts, etc. l Check Voltages l Check Compressor Clutch operation l Check Belts and A/C Hoses l A/C Function Check page 88