If you had a port on the line feeding the exp. valve it would be easy but I doubt there is one.. It could be a bad exp. valve that wont open but if that was so, I would think the low side pressure would be very low or in vaccuum . It sure sounds like a cond. coil problem.. Wonder if the cond. coil is slugged with oil? opening the system and blowing air or Nitrogen thru it would tell you that.. I dunno... I am about out of suggestions.. When you find the problem, I sure would like to know what it was..