[jimh]

I have found a good solution to the lack of low side service port on the air con.
This is for those of us who like to diagnose / top up their own air con.
I have found several mentions of a "tank adaptor" to do this job, but most also mention that although the tank adaptor sort of fits, the threads are loose.

I have found what I think is a better (and cheaper) option.

Buy from Ebay a R12 / R143a low side port adaptor and a M12x1.5 tap.
Both together should be cheaper than the tank adaptor.

You'll see that the thread is slightly too small on the r12/R134a adaptor to fit the A8 low side port. That's what the M12x1.5 tap is for.
I used that to re cut the thread in the adaptor and it fits perfectly.

Unfortunately, the low side port is positioned such that you bruise the back of your left hand on the HVAC air box when starting off screwing the adaptor on, but once the threads are engaged sufficiently to use an open ended spanner, you're golden.