the ac compressor good, fan good switch panel good heater good but the ac not coming on
The ac compressor in my 2004 Toyota Wish 2000cc is not coming on despite the switch light up on the dashboard the fan works to regulate the temperature, but do not come on when you turn on the ac. the heater blows hot air. when turn on. the blower fans works. the compressor will work when test independently. gas was changed to accommodate a different pressure switch in front of the radiator/condenser . what could cause the ac from not working? the engine was repaired after a blown cylinder head gasket. difficulty in restarting. computer was removed and put back. now driving but no ac. grateful for your help