Thanks for the responses,

Just an update, I picked up the evaporator/Tx valve from the a/c people, and yes, it did have a little oxidation (the Tx valve is brass and the pipe it connects to is Aluminium), but it only took me 10 minutes to work the joint and take it apart.

The good news is it has saved me $700.

In one of the US bulletins on changing the a/c gas from R12 to the environmentally safe gases, it mentioned changing one of the flexible hoses by the compressor. How important is this? The a/c people I'm using (Subaru recommended) can't understand why...

Bruce