The sealed accumulator assembly connects to the evaporator outlet pipe. The sealed accumulator assembly functions as a liquid/vapor separator that receives the following:

The sealed accumulator assembly only allows the refrigerant vapor and the refrigerant oil to flow to the compressor.

At the bottom of the accumulator is a desiccant that acts as a drying agent for moisture that may enter the system. An oil bleed hole, located near the bottom of the accumulator outlet pipe, provides an oil return path to the compressor.

A low-side pressure service fitting is located on the accumulator. A similar service fitting is provided for mounting the cycling pressure switch. Do not to discharge the system when replacing the switch. Service the accumulator only as a replacement assembly.

The Harrison HT-6 compressor is belt-driven by 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 applied voltage energizes the clutch coil, a clutch plate and hub assembly move rearward toward the compressor clutch pulley. The magnetic force locks the clutch plate and the compressor clutch pulley together as one unit in order to drive the compressor shaft.

All the replacement compressors from the service parts have 240 ml (8 fl oz) of oil in the crankcase. When replacing the compressors, drain the oil from the old compressor into an approved container. Note the amount drained. Drain the oil from the new compressor. Then, fill the new compressor with new oil in the same amount that was drained from the old compressor.

Do not strike, drop, or turn the compressor upside down. If the compressor is knocked over or turned upside down, rotate the compressor's clutch at least 6 times by hand in order to circulate the oil which has settled in the cylinder. Sudden rotation with oil in the cylinder will cause damage and adversely affect durability.

The condenser assembly in front of the radiator consists of coils that carry the refrigerant, and cooling fins, that provide the rapid transfer of heat. Air passing through the condenser cools the high-pressure refrigerant vapor, causing condensation.

The plastic expansion tube, with the mesh screen and orifice is in the condenser outlet pipe in all the models, except the models with rear air conditioning (RPO C69). Models equipped with rear air conditioning use a Y-shaped junction block in the tube between the condenser and the front evaporator. The junction block is near the right side of the radiator support. The expansion tube (2) is between the junction block and the front evaporator. Refer to Auxiliary Expansion (Orifice) Tube Replacement or HVAC Component Views .

The orifice tube 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 filter screens on both the inlet and outlet sides protect the expansion tube and orifice from contamination. Service the tube only as a replacement assembly.

When the engine is turned OFF with the air conditioning operating, the refrigerant in the system flows from the high-pressure side of the expansion tube orifice to the low-pressure side until the pressure moves towards equalization. This is detectable as a faint hissing sound for 30-60 seconds. The hissing is normal

When system diagnostics indicate a restricted expansion tube, replacement of the restricted expansion tube may not be necessary. Metal chips, flakes, or slivers found on the screen may be removed with compressed air. Reuse the expansion tube under the following conditions:

The rear air conditioning system uses a Thermal Expansion Valve (TXV). The valve consists of the following components:

At the high pressure liquid inlet a fine mesh screen prevents dirt, filings or other foreign material from entering the valve orifice.

When the valve is connected in the system, high pressure liquid refrigerant enters the valve through the screen from the condenser. The high pressure liquid refrigerant then passes to the seat and the orifice, where the refrigerant changes into a low pressure liquid.

The low pressure liquid leaves the valve and flows into the rear evaporator core, where the liquid absorbs heat from the rear evaporator core. There, the liquid changes to a low pressure vapor and leaves the rear evaporator core. The capillary tube is clamped to the low pressure vapor line just below the outlet of the rear evaporator. The capillary tube is held in contact with the rear evaporator outlet tube by a metal clip placed near the end of the tube.

The evaporator cools and dehumidifies the air before the air enters the vehicle. High pressure liquid refrigerant flows through the orifice tube (front system) or TXV (rear system) into the low pressure area of 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. When the process of heat loss from the air to the evaporator core surface takes place, any moisture in the air condenses on the outside surface of the evaporator core. This condensed moisture drains as water.

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

The compressor has a pressure relief valve as a safety factor. Under certain conditions, the refrigerant on the discharge side may exceed the designed operating pressure. Exceeding this pressure limit may cause refrigerant loss out of the pressure relief valve. In order to prevent refrigerant loss or compressor damage, the high pressure cutoff switch opens automatically at approximately 2758 kPa (400 psi). Opening the switch interrupts the current to the compressor clutch. Any condition that causes the opening of the switch keeps the compressor from operating.

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.

Like the coolant in the engine cooling system, the refrigerant 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, some automotive air conditioning systems use a type called Refrigerant-12 (R-12)

This vehicle uses Refrigerant 134-a (R-134a). R-134a is a non-toxic, non-flammable, clear 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.

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