Refrigeration System
A/C System Typical:
CAUTION: Avoid breathing A/C Refrigerant-134a and lubricant vapor or mist. Exposure may irritate eyes, nose, and throat. To remove R-134a from the A/C system, use service equipment certified to meet the requirements of SAE J2210 (R-134a recycling equipment). If accidental system discharge occurs, ventilate work area before resuming service. Additional health and safety information may be obtained from refrigerant and lubricant manufacturers.
Refrigerant-134a, like the coolant in the engine cooling system, is the substance in the air conditioning system that absorbs, carries, and then releases heat. Although various substances are used as refrigerants in other types of refrigeration systems, past automotive air conditioning systems used a type called Refrigerant-12 (R-12). This vehicle uses a new type of refrigerant called Refrigerant-134a (R-134a). it is a non-toxic, non-flammable, clear, colorless, liquefied gas. While the R-134a A/C system is very similar to an R-12 A/C system, the differences in the refrigerant, lubricants, and service equipment are important.
NOTICE: R-134a refrigerant is not compatible with R-12 refrigerant in an air conditioning system. R-12 in an R-134a system will cause compressor failure, refrigerant oil sludge, or poor air conditioning system performance. Refrigerant-134a carries a charge of special lubricating oil, polyalkylene glycol (PAG) synthetic refrigerant oil. GM PAG refrigerant oil will have a slight blue tint. The oil is hydroscopic (absorbs water from the atmosphere) and should be stored in closed containers. Use only polyalkylene glycol (PAG) synthetic refrigerant oil for internal circulation through the R-134a A/C system and only mineral base 525 viscosity refrigerant oil on fittings threads and O-rings. If lubricants other than those specified are used, compressor failure and/or fitting seizure is likely to occur.
Air Conditioning Compressor
The air conditioning compressor is driven by a belt from the engine crankshaft through the compressor clutch pulley. The compressor pulley rotates freely, without turning the compressor shaft, until an electromagnetic clutch coil is energized. When voltage is applied to energize the clutch coil, a clutch plate and hub is drawn toward the pulley. The magnetic force locks the clutch plate and pulley together as one unit to drive the compressor shaft.
Air Conditioning Condenser
The air conditioning condenser in front of the radiator is made up of coils, which carry the refrigerant, and cooling fins to provide rapid transfer of heat. The air passing through the condenser cools the high-pressure refrigerant vapor, causing it to condense into a liquid.
Electric Cooling Fans
Cooling fan operation is crucial to the proper operation of the air conditioning system. The cooling fans ensure the proper amount of airflow across the condenser throughout the vehicle operating range.
Fan operation should be checked during any air conditioning diagnosis procedure. Special attention should be given to the fans whenever excessive high side pressures are encountered.
Air Conditioning Evaporator
The evaporator is a device which cools and dehumidifies the air before it enters the vehicle. High-pressure refrigerant flows through the expansion (orifice) tube and becomes low-pressure refrigerant before entering the evaporator. The heat in the air passing through the evaporator core is lost to the cooler surface of the core, thereby cooling the air As the process of heat loss from the air to the evaporator core surface is taking place, any moisture (humidity) in the air condenses on the outside of the evaporator core and is drained off as water.
High Pressure Relief Valve
The compressor is equipped with a pressure relief valve which is placed in the system as a safety factor. Under certain conditions, the refrigerant on the discharge side may exceed the designed operating pressure. To prevent system damage, the valve is designed to open automatically at approximately 3036 kPa (455 to 525 psi.). Any condition that causes this valve to open should be corrected, and any expelled refrigerant oil should be replaced. The air conditioning refrigerant pressure sensor should also be checked for proper calibration.
Expansion (Orifice) Tube
The plastic expansion (orifice) tube, with its mesh screen and orifice, is located between the condenser outlet and evaporator inlet. It provides a restriction to the high-pressure liquid refrigerant in the liquid line, metering the flow of refrigerant to the evaporator as a low-pressure liquid. The expansion (orifice) tube and orifice are protected from contamination by filter screens on both inlet and outlet sides. When system diagnostics indicate a restricted expansion (orifice) tube, it may not be necessary to replace the tube. Metal chips, flakes, or slivers found on the screen may be removed with compressed air and the expansion (orifice) tube may be reused if:
^ The plastic frame is not broken.
^ The brass expansion (orifice) tube is not damaged or plugged.
^ The screen material is not torn.
^ The screen is not plugged with fine gritty material.
Muffler
Compressor Condenser Hose Assembly Muffler:
A muffler is used on the refrigerant systems to reduce compressor noises and high-pressure line vibrations.
Accumulator
Connected to the evaporator outlet pipe, the sealed accumulator acts as a refrigerant storage container receiving vapor and some liquid and refrigerant oil from the evaporator. At the bottom of the accumulator is the desiccant which acts as a drying agent for moisture that may be trapped in the system. An oil bleed hole is also located near the bottom of the accumulator outlet pipe to provide an oil return path to the compressor. The accumulator is serviced only as a replacement.