The refrigerant functions like the coolant in the engine cooling system. The refrigerant is the substance in the air conditioning (A/C) system that absorbs, carries, and then releases heat. Although various substances may be used as refrigerants in other types of refrigeration systems, some truck and automotive A/C systems use a type of refrigerant called Refrigerant-12 (R-12).

These vehicles, however, use Refrigerant-134a (R-134a) which has the following properties:

While the R-134a A/C system is very similar to the R-12 system, the differences in the refrigerant, the lubricants, and the service equipment are important.

Notice: R-12 refrigerant and R-134a refrigerant must never be mixed, even in the smallest of amounts, as they are incompatible with each other. If the refrigerants are mixed, compressor failure is likely to occur. Refer to the manufacturer instructions included with the service equipment before servicing.

Important: Polyalkaline glycol (PAG) refrigerant oil distributed by General Motors is manufactured with blue coloring. If the color of PAG oil changes to any color other than blue during storage, replace the PAG oil. PAG oil that is no longer blue has absorbed moisture and cannot be used.

R-134a carries a special lubricant called polyalkaline glycol (PAG) refrigerant oil. GM P/N 12345923 PAG refrigerant oil will have a slight blue tint. The oil is hygroscopic, meaning the oil absorbs water from the atmosphere. Store the PAG refrigerant oil in closed containers.