The efficient operation and life of the air conditioning (A/C) system is dependent upon the chemical stability of the refrigeration system. When foreign materials, such as dirt, air, or moisture, contaminate the refrigeration system, they will change the stability of the refrigerant and the polyalkalene glycol (PAG) compressor oil. They will also affect the pressure-temperature relationship, reduce efficient operation, and can possibly cause interior corrosion and abnormal wear of moving parts.

Observe the following practices to ensure chemical stability in the system:

All service parts are dehydrated and sealed before shipping. They should remain sealed until just before making connections. All the parts should be at room temperature before uncapping. This prevents condensation of moisture from the air from entering the system. Reseal all parts as soon as possible if the caps have been removed but the connections cannot be made promptly.

Caution: Avoid breathing the A/C Refrigerant 134a (R-134a) and the lubricant vapor or the mist. Exposure may irritate the eyes, nose, and throat. Work in a well ventilated area. In order to remove R-134a from the A/C system, use service equipment that is certified to meet the requirements of SAE J 2210 (R-134a recycling equipment). If an accidental system discharge occurs, ventilate the work area before continuing service. Additional health and safety information may be obtained from the refrigerant and lubricant manufacturers.

Caution: Refer to Protective Goggles and Glove Caution in the Preface section.

A charging station discharges, evacuates, and recharges an A/C system with one hookup.

Filtering the refrigerant during the recovery cycle together with filtering during the evacuation cycle ensures a supply of clean, dry refrigerant for A/C system charging.

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.

There are many charging stations available. All perform the various tasks required to discharge the system and recover refrigerant, evacuate the system, add a measured amount of oil, and recharge an air conditioning system with a measured amount of refrigerant. Refer to the manufacturer's instructions for all initial setup procedures and all maintenance procedures.

A charging station will have controls and indicators to allow the operator to control and monitor the operation in progress. Refer to the manufacturer's instructions for details. These can be expected to include the following:

1. Main power switch--Supplies electrical power to the control panel
2. Display

•	Shows the time programmed for vacuum

•	Shows the weight of the refrigerant programmed for recharging

•	Refer to the manufacturer's instructions for detailed programming information.

3. Low-side manifold gage--Shows the system's low-side pressure
4. High-side manifold gage--Shows the system's high-side pressure
5. Control panel--Controls the various operating functions
6. Low-side valve--Connects the low side of the A/C system to the unit
7. Moisture indicator--Shows whether the refrigerant is wet or dry
8. High-side valve--Connects the high side of the A/C system to the unit

Important: Use only a refrigerant tank that is designed for the charging station in use. The unit's overfill limitation mechanism is calibrated specifically for use with this tank. The tank valves are also manufactured specifically for this unit.

1. Attach the high-side hose with the quick disconnect coupler to the high-side fitting of the vehicle A/C system.
2. Open the coupler valve.
3. Attach the low-side hose with the quick disconnect coupler to the low-side fitting of the vehicle A/C system.
4. Open the coupler valve.
5. Inspect the high-side and the low-side gages on the unit control panel to ensure that the A/C system has pressure. If there is no pressure, there is no refrigerant in the system to recover.

Important: If there is no refrigerant in the system, do not continue with the recovery operation. Under this condition, this would draw air into the recovery tank.

6. Open both the high-side and low-side valves.
7. Open the gas and the liquid valves on the tank.
8. Drain any oil that may be in the oil separator.
9. Close the oil drain valve.
10. Plug the unit into the proper voltage outlet.
11. Turn ON the main power switch.

Notice: Do not mix the old PAG oil with new PAG oil. The old oil may have aluminum deposits or other foreign material mixed in the oil. Always use new refrigerant PAG oil when refilling the A/C system. Dispose of the used refrigerant oil properly.

12. Begin the recovery process. Refer to the manufacturer's instructions for the charging station in use.

Important: Some A/C system PAG lubricating oil may be removed with the refrigerant during recovery. The amount of oil removed varies. A charging station separates the oil from the refrigerant and provides a means of determining how much oil was removed. Replace the same amount of oil when recharging the system.

Refer to the manufacturer's instructions for the charging station in use.
13. Wait 5 minutes, then check the control panel low-side gage. If the A/C has maintained vacuum, the recovery is complete.
14. If the low-side gage pressure rises above 0, there is more refrigerant in the system. Recover the additional refrigerant. Repeat this step until the system maintains vacuum for 2 minutes.

Important: If the control indicator shows that the refrigerant tank is full during the recovery process and the unit shuts off, install an empty unit tank to store the refrigerant needed for steps later in the procedure. Do not use any other type of tank.

The unit tank must contain a sufficient amount of R-134a refrigerant for charging. Measure the amount of refrigerant in the tank. If there is less than 3.6 kg (8 lb) of refrigerant, add new refrigerant to the tank. Refer to the manufacturer's instructions for adding refrigerant.

1. Verify that the high-side and the low-side hoses are connected to the A/C system. Open both the high-side and the low-side valves on the unit control panel.
2. Open both the gas and the liquid valves on the tank.

Important: Refer to the manufacturer's instructions for the charging station in use. It is necessary to evacuate the system before recharging it with new or recycled refrigerant.

3. Start the vacuum pump and begin the evacuation process. Non-condesable gases, mostly air, are vented from the tank automatically during the recycling process. The pressure being released may be heard.

Important: Change the vacuum pump oil frequently. Refer to the manufacturer's instructions for the charging station in use.

4. Inspect for leaks in the system. Refer to the manufacturer's instructions for the charging station in use.

Any oil removed from the A/C system during the recovery process must be replenished at this time.

1. Use the correct graduated bottle of PAG oil for the R-134a system.

Important: Refer to the manufacturer's instructions for the charging station in use. Add the proper amount of PAG oil to the system.

2. Close the valve when the required oil charge has been pulled into the system.

Important: Evacuate the A/C system before charging.

1. Close the low-side valve on the control panel.
2. Close the high-side valve on the control panel.
3. Refer to the manufacturer's instructions for the charging station in use.
4. Enter the amount of refrigerant needed to charge the A/C, making sure to use the correct system of measurement, i.e. kilogram (kg) or pound (lb).
5. Begin the charging process.

1. Close the high-side valve on the unit control panel. Both valves should be closed.
2. Start the vehicle and the A/C system.
3. Let the engine run until the readings on the high-side and low-side gages stabilize.
4. Compare the readings to the system specifications.
5. Measure the evaporator outlet temperature to ensure that the A/C system is operating within the system specifications.
6. Keep the A/C running.
7. Close the high-side coupler valve.
8. Disconnect the high-side hose from the vehicle.
9. Open the high-side and low-side valves on the control panel.
10. The system will quickly draw in refrigerant from both hoses through the low-side hose.
11. Close the low-side coupler valve.
12. Disconnect the low-side hose from the vehicle.

Sometimes the total charge does not transfer into the A/C system. There are 2 reasons why this may occur:

1. The pressure in the unit's tank and the pressure in the A/C system are roughly equal.

•	This will cause the transfer to proceed too slowly.

•	Refer to the manufacturer's instructions for the charging station in use.

2. There was not enough refrigerant in the unit's tank to transfer the full charge.

•	It is necessary to recover the partial charge of refrigerant from the vehicle and then evacuate and charge the A/C system again.

•	Refer to the manufacturer's instructions for the charging station in use.