I am not a Air Cond. expert.....but the only way you can really tell the charge status is with the pump running (clutch engaged). Sitting for 2 years ??...More than likely you are undercharged and low pressure switch (if it has one) will not allow the clutch to engage. I have had to by-pass the switch to fill a empty system...other wise the pump would never turn...and suck in the freon.
Hey.... that is my 2 cents worth!! <img src="/forums/images/graemlins/cheers.gif" alt="" />