My buisness is refrigeration /air conditioning
Dont put Compressed air in the system, always has water in it, and one little droplet of water can cause yuo so many problems. Dry Nitrogen is the best to use, then you can listen for leaks, and use a soapy water over joints to see if they bubble. In a EA it would more than likely still be an R12 system, unless it was retrofitted. All seals will last underthe pressure, the problem being that with R134a, you need a diffent oil, so depending on the type of seal, you may get a blown seal, as the new oil may be incompatable. Really do need someone with guages and a vacumn pump to do the work for you.
Hope this helps
2002 Narooma Blue Manual TS50