Subaru 2009 IMPREZA Service Manual page 2704

Refrigerant Charging Procedure
HVAC SYSTEM (HEATER, VENTILATOR AND A/C)
21) To prevent damage to the compressor, push
the A/C switch ON-OFF quickly a few times.
22) Set up the vehicle to the following status:
CAUTION:
When filling with the engine running, do not
open the high pressure side valve.
Always fill from the low pressure side valve.
• A/C switch ON
• Engine running at 1,500 rpm
• Blower speed setting to "HI"
• Temperature setting to "MAX COOL"
• Air inlet setting to "RECIRC"
• Window open
23) Open the low pressure side valve and fill with
refrigerant up to the specified amount.
24) After filling with refrigerant, close all valves and
disconnect the hose from the service port.
25) Attach the cap to the service port.
AC-24