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 3036 kPa (440 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.