The a/c on my 2001 A4 1.8tq is weaker than it was last year which was weaker than the year before. It now takes about 20 minutes before the car is cool. My guess is that the refrigerant is slowly leaking out. My plan is to use a Wally-world R134a kit to recharge it. Does anyone have an idea of what the low-side pressure should be? Thanks. Peter