My AC has started acting very strange. It works perfectly fine while running or idling in park but at stop sign or red light it blow hot air. The high side is at about 325 lbs. but fluctuates 5 to 10 lbs in both directions. The low side is steady at about 35 lbs. There is condensation around the dash vents and the drain keeps plugging and filling the passenger side floor board, I mean fill, I shop vac standing water out of it every day. I live in the South and the temp is around 90 to 100 every day already. Are these the signs of a bad expansion valve? If so, where is it and how do you change it?