AirCon stopped working - Where is the sight glass ?

 G'day all,
had the A/c serviced a couple of years ago and it was working beautifully last summer. The other day I turned it on and just ambient temp. I have had the A/c dismounted and twisted to push out of the way while working on something else, so not sure if I've created a leak, or broken the 12v wire to the compressor clutch.
 Mine is JDM import and my manual (US) shows a sight glass as step 1 for checking gas. I can't find it. 
Is there a way to tell if the compressor is spinning ? ie 12v has engaged the clutch.  Perhaps resting your hand on the outside when someone turns it on, a difference can be felt ? I presume the compressor heats up normally, but that may be hard to attribute since the turbo / downpipe is nearby. 
 I also have seen some hits where people have said only works on Max fan or only on Recirc,  I have not checked my settings, but other cars don't seem to require that.
 Any tips ? thanks

Thanks Ian, found the sight glass under a blue lid where the gas is filled. Ran the car, turned on the A/C and the revs kicked up to about 1500 rpm, after a min or so I looked in the sight glass, no bubbles - or no fluid, hard to tell. Does the fluid have a colour, cause this is clear, or missing. It seems I'll get the mobile service who reco'd it for me to do another leak test.
 Thanks.