Porsche aircon

[kevin-3r6u6]

Hi I've got boxster 986 s
Problem I've got is a funny wurring noise comes from behind the central dash when aircon is on system is full runs cold but this noise is doing my head in any ideas anyone

[STiG911]

You've either got an air bubble in the system, or it's low on oil.
Mine made a similar noise a few years back until I got the system drained down and refilled. Tech said it didn't have enough oil in it, so the compressor was running hotter than normal as a result.

[DJMC]

Does the noise stop when the fan is switched to "off"?