R 30 P/U 2WD V6-262 4.3L (1987)
Refrigerant: Technical Service Bulletins
A/C - Retrofitting R-12 Vehicles to R-134A
Group Ref.: HVAC
Bulletin No.: 331226
Date: January, 1994
INFORMATION
SUBJECT:
RETROFITTING R-12 VEHICLES TO R-134a
MODELS:
1994 AND PRIOR YEARS, PASSENGER CARS AND TRUCKS WITH R-12 A/C SYSTEMS
There has been a great deal of information presented by the media regarding the need to retrofit vehicles produced with R-12, to a substitute refrigerant.
This bulletin will outline GM's position and future plans on this subject.
Most important, there is currently NO requirement to retrofit any R-12 vehicle. Vehicles built with R-12 can be serviced with R-12, as long as the
refrigerant is available. At some point in time, R-12 may become either too scarce or too expensive to economically justify service on some vehicles with
R-12. By that time, GM will provide you with instructions on retrofitting those vehicles from R-12 to R-134a.
GM vehicle divisions, platforms, and component suppliers have been actively working on the details of retrofitting R-12 vehicles. An enormous amount
of work is required to determine how hundreds of vehicle models can be satisfactorily retrofitted. Additional information will be provided as it becomes
available.
The following items contain important technical information that should answer many of the questions, and correct some misconceptions reported in the
media.
SUBSTITUTE REFRIGERANTS
R-134a is the only approved substitute refrigerant that GM recommends and it should only be used if a complete retrofit procedure has been performed.
None of the other refrigerants currently being marketed as replacement or drop-in substitutes for R-12 are approved for use in GM vehicles.
R-12 and R-134a are not interchangeable. R-134a cannot be added to fill a low R-12 system. The combination of the two materials can cause high
system pressures, which could cause damage to the system.
Retrofitting an R-12 vehicle to R-134a requires careful preparation to insure that neither the vehicle nor the A/C service equipment has become
contaminated.
RESIDUAL MINERAL OIL
The concern that mineral oil is chemically incompatible with R-134a and/or PAG lubricant has been proven to be untrue. A normal charge of mineral oil
left in the A/C system after a retrofit to R-134a will not damage the system. Mineral oil, however, does not mix well with R-134a, and will not provide
adequate lubrication. Tests on both the orifice tube and TXV systems show that the mineral oil parks in places such as the accumulator, and does not
appreciably affect performance or damage the system. The retrofit service bulletin will specify the correct oil to be used. It is important that this oil
recommendation be followed carefully.
RESIDUAL R-12
Residual R-12 left in a system, due to improper retrofit service procedures, may result in system damage unless the residual R-12 is kept below the 2
percent limit specified by the Society of Automotive Engineers' Specification J-1661. New service methods are being developed to minimize the level of
R-12 remaining in the A/C system after the retrofit procedure is completed. Following these new procedures will be critical to insure that the above limits
are met.
SYSTEM FLUSHING
R-11, a material commonly used as an A/C system flushing solvent, has been found to be chemically incompatible with PAG lubricant. Technicians
should be aware that residual R-11 remaining in an R-12 system will be very damaging if the vehicle is retrofitted to R-134a later in its life. For many
years GM has recommended the use of in-line filters as an alternative to system flushing.
SYSTEM FLUSHING, USING EITHER R-11 OR ANY OTHER FLUSHING MATERIAL, IS NOT APPROVED BY GM FOR ANY A/C SYSTEM.
DESICCANT PROTECTION
