REFRIGERATION SYSTEM n Chapter 4 n Classroom Manual n Page 67

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

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

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

ACSYSTEMACSYSTEM Low side High side Expansion Valve

SYSTEM DIAGNOSIS n Knowing the ambient air temperature. n Determine normal HIGH side pressure. n There are seven conditions for A/C systems. n 1 normal condition. n 6 conditions that indicate a malfunction.

NORMAL OPERATION n Low-side gauge: Normal pressure –CFC-12: PSI –HFC-134a: PSI n High-side gauge: Normal pressure –CFC-12: PSI –HFC-134a: PSI

PLATE 1 n Normal refrigerant charge expansion valve system. n Receiver/ Dryer in high side of system.

PLATE 9 n Normal refrigerant charge orifice tube system. n Accumulator in low side.

REFRIGERANT n Refrigerant is the term used when referring to the fluid that is used in an automotive air conditioning system. n “a gas used in a mechanical refrigeration system” page 77

R-12 (CFC-12) n Dichlorodifluoromehtane is CFC-12 n Safe to Humans n Can withstand high pressures without decomposing or deteriorating n Boiling Point is degree Fahrenheit n Does not react with A/C components n Soluble in mineral oil

Temperature and Pressure Relationship of CFC-12 n Freon temperature and degrees Fahrenheit are roughly the same from 20 to 70 degrees. n A gauge reading of 28 PSI equals a refrigerant temperature of 30 degrees. page 78

134a n New Refrigerant to replace CFC-12. n Tetrafluoroethane (R-134a) n Is a hydroflourocarbon (HFC) n Does not contain chlorine. n Molecules are 11 times smaller so must use barrier type refrigerant hoses. page 78

R-22 for LEAK TESTING n R-12 = 50psi n R-22 = 100psi n Do NOT mix refrigerants n R-22 is NOT a replacement for R-12 n Small amounts of R-22 used in leak testing can be vented to atmosphere. page 82

HANDLING REFRIGERANTS n All refrigerants must be properly stored, handled, and used. n Do NOT expose containers to flame. n Burning refrigerant creates poisonous gas. n Pound cans can NOT be identified by color. n Do NOT mix refrigerants. page 82

n Wear safety glasses or goggles at all times. n Do NOT vent freon in a confined space. n Avoid breathing these or any other fumes. n HFC-134a is combustible. n Do NOT pressure test A/C system with shop air. SAFETY PRECAUTIONS page 84

OTHER REFRIGERANTS n Use R-12 in R-12 systems. n Use R-134a in R134a systems. n R134a is the only legal replacement for R-12 after proper retrofit procedures. page 86

REFRIGERATION OIL n R-12 uses mineral oil. n R134a uses PAG oil. n Ester Oil can be used in conversions. n Small Quantities of Mineral oil can be mixed with Ester oil. n Mineral oil and PAG oil are not mixable. page 86

SERVICING TIPS n A/C oil level should be checked each time the system is drained. n Keep the cap on oil container. n Refrigerant oil is hygroscopic. n Moisture is damaging to A/C system.

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