Refrigeration System

Caution: Avoid breathing A/C Refrigerant-134a and lubricant vapor and 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.

Notice: R-134a refrigerant is not compatible with R-12 refrigerant in an air conditioning system. R-12 in a R-134a system will cause A/C compressor failure, refrigerant oil sludge, or poor air conditioning system performance.

The refrigerant is the substance in the air conditioning system that absorbs, carries and releases heat. Although various substances are used as refrigerants in other types of refrigeration systems past automotive air conditioning systems used Refrigerant-12 (R-12).
This vehicle uses Refrigerant-134a (R-134a), R-134a has the following features:

- Non-toxic
- Nom-flammable
- Clear
- Colorless
- Liquefied gas

Refrigerant-134a carries a charge of a special lubricant, polyalkaline glycol (PAG) refrigerant oil. GM PAG refrigerant oil has a slight blue tint. The oil is hydroscopic (absorbs water from the atmosphere) Store R-134a in closed containers

Handling Refrigerant R-134a

Caution: Avoid breathing A/C Refrigerant-134a and lubricant vapor and 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 the work area before resuming service. Additional health and safety information may be obtained from the refrigerant and lubricant manufacturers.

Important:
- Do not mix R-12 refrigerant and R-134a refrigerant, even in the smallest amounts. R12 and R-134a are incompatible with each other. If the refrigerants are mixed, compressor failure is likely to occur.
- Use only the specified lubricant (PAG) for the R-134a A/C system and R-134a components. If you use lubricants other than those specified, compressor failure is likely to occur. Coat all the fittings and the O-ring seals with clean 525 viscosity refrigerant oil in order to provide a leak-proof seal and in order to aid in assembly and disassembly.
- Do not store or heat the refrigerant containers above 52 °C (125 °F).
- Do not heat a refrigerant container with an open flame. If the container must be warmed, place the bottom of the container in a pail of warm water.
- Do NOT intentionally do the following to the refrigerant containers:
- Drop
- Puncture
- Incinerate
- Refrigerant will displace oxygen. Work in well ventilated areas in order to prevent suffocation.
- Do NOT introduce compressed air to any refrigerant container or refrigerant component. Contamination will occur.
- If you must carry a container of DOT CFR Refrigerant-134a in a vehicle, do not carry the refrigerant in the passenger compartment.

All of the Refrigerant-134a disposable, blue containers are shipped with a heavy metal screw cap in order to protect the valve and the safety plug of the container from damage. Replace the cap after each use of the container in order to continue the protection.

Expansion (Orifice) Tube Description

The plastic expansion tube contains a fixed diameter tube. The tube has a mesh filter screen at either end. The expansion tube is located in the evaporator inlet pipe. The expansion tube creates a restriction to the high-pressure liquid refrigerant in the liquid line. The flow of the refrigerant is then metered to the evaporator as a low-pressure liquid. When the engine is turned OFF while the air conditioning is operating the refrigerant in the system continues to flow.

The refrigerant flows from the high-pressure side of the expansion tube (orifice) to the low pressure side until the pressure is equalized. The equalization may be detected as a faint sound of liquid flowing (hissing) for 30-60 seconds. This is a normal condition. You may not need to replace the expansion tube when the system diagnostics indicate a restricted expansion tube. Remove the following materials found on the screen with compressed air:

- Metal chips
- Metal flakes
- Metal slivers

You may reuse the expansion tube under the following conditions:

- The plastic frame is not broken.
- The expansion tube is not damaged or plugged.
- The screen material is not worn.
- The screen is not plugged with fine gritty material.

Evaporator Description

The evaporator cools and humidifies the air before the air enters the vehicle. High pressure liquid refrigerant flows through the orifice tube into the low-pressure area of the evaporator. The heat in the air that passes through the evaporator core is lost to the cooler surface of the core, thereby cooling the air. During this time any moisture (humidity) in the air condenses on the outside surface of the evaporator core. The condensed moisture is drained off as water.

Condenser Description

The header tube and center type condenser is made of cross tube and cooling fins. The cross tubes carry the refrigerant. The cooling fins provide a rapid transfer of heat. The air passing through the condenser cools the high-pressure refrigerant vapor, causing the vapor to condense into a liquid.

Accumulator Description

The accumulator functions as a liquid/vapor separator. The accumulator receives the following items from the evaporator:

- Refrigerant vapor
- Some liquid refrigerant
- Refrigerant oil

The accumulator only allows the refrigerant vapor and the oil to continue on the compressor.

Desiccant at the bottom of the accumulator acts as a drying agent for moisture that may have entered the system. An oil bleed hole is located near the bottom of the accumulator outlet pipe. The oil bleed hole provides an oil return path to the compressor.

The accumulator is serviced only as a replacement assembly.

Heater Core Description

The heater core heats the cool, dehumidified air in any air conditioning mode. This achieves the desired temperature. The position of the control assembly temperature knob determines how much heat is added to the incoming air.

Compressor Description

Compressors are belt driven from the engine crankshaft through the compressor clutch pulley. The compressor pulley rotates freely without turning the compressor shaft until the electromagnetic coil is energized. When voltage is applied in order to energize the clutch coil, a clutch plate and hub assembly is drawn rearward toward the pulley. The magnetic force locks the clutch plate and the pulley together as one unit in order to drive the compressor shaft.

All of the replacement compressors from service parts will have oil in the crankcase. Drain and retain the oil. When you replace the oil, use the same amount of oil that was used in the old compressor.