IIRC, I think the low pressure gauge should be in the 25-40 range, depending on various factors. Don't hold me to this, since I'm going from memory, but I think that 70-100 is quite a bit too high. Some of our CEG'ers are AC experts, and I'm sure they can give you some precise info, but maybe this will give you some help in the meantime.

95 Contour Zetec, ATX (wrecked, sitting in the barn) 95 Mystique Zetec, MTX 2000 Taurus SEL 3.0L Duratec 1994 Crown Victoria LX 4.6 V8 1993 Chevy Silverado 4.3 V6