The efficient operation and the 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 polyalkaline 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.

Discharging, Adding Oil, Evacuating, and Charging Procedures for A/C System

Warning: To prevent personal injury, avoid breathing A/C Refrigerant and lubricant vapor or mist. Work in a well ventilated area. To remove refrigerant from the A/C System, use service equipment designed for recovery that is certified to meet the requirements of the appropriate SAE Standards. If an accidental system discharge occurs, ventilate the work area before continuing service. Additional health and safety information may be obtained from the refrigerant, refrigerant recovery, and lubricant manufacturers.

Warning: Refer to Protective Goggles and Glove Warning 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.

Charging Station Setup and Maintenance

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 A/C system with a measured amount of refrigerant. Refer to the manufacturer's instructions for all initial setup procedures and all maintenance procedures.

Control Panel Functions

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:

Main Power Switch: The main power switch supplies electrical power to the control panel.

Display: The display shows the time programmed for vacuum and the weight of the refrigerant programmed for recharging. Refer to the manufacturer instructions for detailed programming information.

Low Side Manifold Gage: This gage shows the system low side pressure.

High Side Manifold Gage: This gage shows the system high side pressure.

Controls Panel: This contains the controls that control the various operating functions.

Low Side Valve: This valve connects the low side of the A/C system to the unit.

Moisture Indicator: This indicator shows if the refrigerant is wet or dry.

High Side Valve: This valve connects the high side of the A/C system to the unit.

Refrigerant Recovery

Note: Use only a refrigerant tank that is designed for the charging station in use. The unit 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.

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

5. Check the high-side and the low-side gages on the unit control panel in order to ensure that the A/C system has pressure. If there is no pressure, there is no refrigerant in the system to recover.
6. Open both the high-side and the 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.

Caution: 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.

Note: 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 instructions for the charging station in use.

12. Begin the recovery process. Refer to the manufacturer 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.

Note: 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.

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.

Evacuation

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

Note: Refer to the manufacturer 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-condensable gases, mostly air, are vented from the tank automatically during the recycling process. You may hear the pressure being released.

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

4. Check for leaks in the system. Refer to the manufacturer instructions for the charging station in use.

A/C System Oil Charge Replenishing

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

Note: 

•	Keep the oil bottles tightly capped at all times to protect the oil from moisture and contamination.

•	You must have an A/C system vacuum for this operation. Never open the oil injection valve while there is positive pressure in the A/C system. This will result in oil blow-back through the bottle vent.

•	Never let the oil level drop below the pickup tube while charging or replenishing the system, as this will allow air into the A/C system.

1. Use the correct graduated bottle of PAG oil for the R-134a system.
2. Refer to the manufacturer instructions for the charging station in use. Add the proper amount of PAG oil to the system.
3. Close the valve when the required oil charge has been pulled into the system.

Charging

Note: Evacuate the A/C system before charging.

1. Close the low-side valve on the control panel.
2. Open the high-side valve on the control panel.
3. Refer to the manufacturer 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.

Successful Transfer Complete

1. Close the high-side valve on the unit's 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 gage and the low-side gage stabilize.
4. Compare the readings to the system specifications.
5. Check 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. The system will quickly draw in refrigerant from both hoses through the low-side hose.
10. Close the low-side coupler valve.
11. Disconnect the low-side hose from the vehicle.

Unsuccessful Transfer

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 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 instructions for the charging station in use.

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

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

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