Evacuating the A/C System

Fig 3 Refrigerant Recovery Machine Hookup:

NOTE: Special effort must be used to prevent moisture from entering the A/C system oil. Moisture in the oil is very difficult to remove and will cause a reliability problem with the compressor.

If a compressor designed to use R-134a refrigerant is left open to the atmosphere for an extended period of time. It is recommended that the refrigerant oil be drained and replaced with new oil or a new compressor be used. This will eliminate the possibility of contaminating the refrigerant system.

If the refrigerant system has been open to the atmosphere, it must be evacuated before the system can be filled. Moisture and air mixed with the refrigerant will raise the compressor head pressure above acceptable operating levels. This will reduce the performance of the air conditioner and damage the compressor. Moisture will boil at near room temperature when exposed to vacuum. To evacuate the refrigerant system:

NOTE: When connecting the service equipment coupling to the line fitting, verify that the valve of the coupling is fully closed. This will reduce the amount of effort required to make the connection. If connection is still difficult to make refer to TSB #24-02-93.

1. Connect a suitable charging station, refrigerant recovery machine, and a manifold gauge set with vacuum pump.
2. Open suction and discharge valves and start vacuum pump. The vacuum pump should run a minimum of 45 minutes prior to charge, to eliminate all moisture in system. When suction gauge reads -88 kPa (-26 in. Hg) vacuum or greater for 45 minutes, close all valves and turn off vacuum pump. If the system fails to reach specified vacuum, the refrigerant system likely has a leak that must be corrected. If the refrigerant system maintains specified vacuum for at least 30 minutes, start the vacuum pump, open the suction and discharge valves. Then allow the system to evacuate an additional 10 minutes.
3. Close all valves. Turn off and disconnect the vacuum pump.
4. The refrigerant system is prepared to be charged with refrigerant.

R-134a REFRIGERANT
This vehicle uses a new type of refrigerant called R-134a. It is a non-toxic, non-flammable, clear colorless liquefied gas.

R-134a refrigerant is not compatible with R-12 refrigerant in an air conditioning system. Even a small amount of R-12 in a R-134a system could cause compressor failure, refrigerant oil sludging or poor performance. Never add R-12 to a system designed to use R-134a. System failure will occur.

Fig 4 A/C Service Ports:

Both of the service ports to charge the air conditioning system are located on the hoses. New design of service ports have been used to ensure that the system is not accidentally filled with the wrong refrigerant (R-12).

Fig 5 Refrigerant Recovery/Recycling Station -- Typical:

When servicing a system, it is required that an air conditioning charging recovery/recycling machine be used. Contact an automotive service equipment supplier for proper equipment. Refer to the operating instructions provided with the equipment for proper operation.

Fig 6 Manifold Gauge Set -- Typical:

A manifold gauge set must also be used in conjunction with the charging and/or recovery/recycling device. Only use gauges that have not been used for R-12. The service hoses on the gauge set should have manual (turn wheel) or automatic back flow valves at the service port connector ends. This will prevent refrigerant R-134a from being released into the atmosphere.

Fig 7 Underhood Label:

R-134a refrigerant requires a special type of compressor oil. When adding oil, make sure that it is designed to be used in a R-134a system. Refer to the label under the hood for proper oil and refrigerant charge levels.

Due to the different characteristics of R-134a it requires all new service procedures.

WARNING: Avoid breathing a/c refrigerant and lubricant vapor or mist exposure may irritate eyes, nose and throat. Use only approved service equipment meeting SAE requirements to reclaim R-134a systems. If accidental system discharge occurs, ventilate work area before resuming service.

R-134a service equipment or vehicle a/c system should not be pressure tested or leak tested with compressed air. Some mixtures of air and R-l34a have been shown to be combustible at elevated pressures. These mixtures are potentially dangerous and may result in fire or explosion causing injury or property damage.

The use of R-134a will have a positive environmental impact due to it's zero ozone depletion and low global warming impact.