Evacuating Refrigerant System

NOTE: It is necessary to evacuate the air conditioning system any time the system has been opened. Evacuation is necessary to rid the system of all air and moisture that may have been allowed to enter the unit. After installation of a component, the system should be evacuated for approximately 15 minutes. A component in service that has been opened for repair should be evacuated for 30 minutes.




1. Engine should be off.
2. Connect a manifold gauge set to the compressor gauge fittings. Close both high and low pressure valves.
3. Make sure the refrigerant has been discharged from the system.
4. Connect the center hose of the gauge set to the vacuum pump inlet.
5. Start the vacuum pump and then open the high and low manifold pressure valves.
6. After about ten minutes, check that the low pressure gauge reads more than 94.39 kPa (0.96 kg/sq.cm, 13.7 psi) vacuum. If negative pressure can not be obtained, there is a leak in the system. In this case, repair the leak as described in the following.
1. Close both the manifold valves and stop the vacuum pump.
2. Charge system with a can or refrigerant [about 0.4 kg (0.9 lb)]. Refer to Charging Refrigerant.
3. Check for refrigerant leakage with a leak detector. Repair any leakage found. Refer to Checking Refrigerant Leak.
4. Discharge refrigerant again, and then evacuate the system. If no leaks are found, continue evacuating the system.

7. Start the vacuum pump.




8. Open both manifold pressure valves to obtain 94.39 kPa (0.96 kg/sq.cm, 13.7 psi) of vacuum.
9. After the low pressure manifold gauge indicates as close to 94.39 kPa (0.96 kg/sq.cm, 13.7 psi) as possible, continue evacuating for 15 minutes.
10. After evacuating for 15 minutes, close both manifold pressure valves and stop the vacuum pump. Disconnect the hose from the vacuum pump. The system is now ready for charging.