A little knowledge...

Had a phone call from a garage in Swindon that had recently been sold an AirCon station and were offering A/C servicing. They were confused as to why there were 3 different grades of PAG oil. I patiently explained that each compressor needs a specific viscosity dependent upon the compressor design. After a little thought, the guy on the other end of the phone asked, "So do I need to use a thinner oil in Winter then".

I must admit to a little head shaking before I explained  that the internal temperature of the Evaporator is usually constant when the system is working correctly and no, he shouldn't use a thinner oil in Winter.

Ford Mondeo

Low pressure service port tucked neatly under the wheel arch, need to take out the liner to connect.

Ford Fiesta

Even better than the Mondeo, need to take out the headlight to connect to the low pressure service port. Sadly, need to take the front bumper off to remove the headlight, (well, in theory).

Volvo V50

Low pressure port directly under a wing to wing torsion bar, which needs to be removed to connect. (well, in theory).

 Renault  Laguna, Megane, Clio etc

A Classic !  HIGH pressure service port on the LOW side of the system. Designed to confuse and trap the unwary.  Can't complain really, we've had lot's of compressor changes thanks to it.