INTRODUCTION OF R134A A/C SYSTEM (INFORMATIONAL)
SUBJECT: INTRODUCTION OF R134A AIR CONDITIONING SYSTEM (INFORMATIONAL)
MODELS: 1993 W-4 FORWARD/TILTMASTER (WITH 350 GASOLINE ENGINES)
A major change will be incorporated in the Air Conditioning system used in 1993 W4 GAS vehicles. This change involves the use of "Tetraflourethane" (CH2FCF3) more commonly known as R-134a as the A/C system refrigerant.
SYSTEM CHANGES
The A/C system designed for the 1993 W4 GAS vehicles differs from current GM models in several aspects:
* R-1 34a specific refrigerant * Condenser design and/or location change * Hose and piping internal dimensions * Receiver/drier design * Compressor model * Pressure switch control set points * Sight glass removed or invalid for diagnostics * Service ports/fittings are redesigned * Refrigerant charge volume is reduced * Compressor lubricant
SERVICE EQUIPMENT
Because of the incompatibility between R-134a refrigerant/lubricant and R-12 refrigerant/lubricant, R-134a dedicated service equipment is necessary to prevent cross-contamination when servicing the system. The following items are required for proper R-1 34a service:
- ACR4 R134a refrigerant, recovery, recycling and recharging station (J39500). - R12/Rl34a A/C refrigerant leak detector (J39400).
Each of the listed items has been engineered for optimum efficiency when used on R-134a systems, SAE standards specify fitting and hardware differences from R-12 equipment.
R-1 34a PRESSURE/TEMPERATURE CHART
The enclosed refrigerant pressure/temperature card points out how similar R-12 and R-134a are in relation to each other. Actual system operating pres- sures for R-1 34a are virtually the same as current R-12 systems. Pressures are a function of system condenser and evaporator heat transfer capability and must be optimized for each type of refrigerant and each vehicle system.
REFRIGERANT/LUBRICANT
HFC-134a or "R-134a" is the generic identifier for Tetraflourethane (CH2FCF3) refrigerant used in the new A/C systems. R-134a is not compatible with R-12 mineral base lubricants. The correct lubricant for the systems used on GM W4 vehicles is a "polyalkylene glycol" or PAG.
The PAG oil used on GMW4R-134a A/C systems is ZXL 100PG(DH-PS), P/N 2-90188-300-0. This oil is formulated specifically for the swash plate compressor used on GMW4R-134a vehicles and should never be mixed with other lubricants of any type.
Each compressor contains the proper amount of PAG oil for the entire system application. If a compressor service replacement is needed, follow the procedure described in the "Compressor Oil" section of the applicable service manual.
R-134a refrigerant is available through normal supply sources. Use only R-134a specifically intended for "mobile" service applications.
SYSTEM SERVICE PRACTICES
While handling and servicing of R-134a/PAG is very similar to R-12/mineral oil, there are some significant differences. Refer to the ZEXEL R-134a Service Manual for a review of specific safety and handling practices.
Specific service procedures are covered in the appropriate Service Manual. Because of the changes in components and material used in this system, there are service issues which need to be addressed:
* When opening the A/C system, cap or plug all openings to prevent contamination from dirt and air (moisture). PAG has an extreme moisture absorption rate. If the system has been left open the PAG oil remaining in the system will absorb moisture.
* DO NOT Use or depend on a sight glass for charge determination or diagnostics. R-1 34a and PAG Lubricants do not exhibit "clear sight glass" even when properly charged.
* Use only service parts expressly designated for R-1 34a system service.
* Leak detection of R-134a is difficult even with the most sensitive electronic detectors. Move slowly and keep the sensor tip of the detector within 5 mm of the area being checked.
* NEVER mix different grades of PAG oils or mix PAG oil with mineral oil in any A/C system. Compressor failure may occur.
* System evacuation time should be doubled for R-134a systems as compared to R-12 systems.
* PAG oil is supplied in single-use (small quantity) containers to ensure quality. Any PAG oil remaining in the container should be discarded in an environmentally safe manner in accordance with local regulations.
ADDITIONAL INFORMATION
Service parts information and service procedures are covered in their respective publications. A ZEXEL R-134a Service Manual is included with this mailing which covers R-134a technical issues and practices in detail.
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.
