I purchased a house in Arkansas (hot/humid summers) with central heat/air last August; it has an older AC unit that was charged with freon in Oct. Recently I have noticed that when the AC is running, there is a drip in the wall not far from the indoor unit. Sounds like it's dripping from ceiling to floor inside the wall. The ducts are all in the floor, so I don't think it's condensation on the ducts, but it seems to be condensation somewhere. The repair guy came back last week to check, and went up in the attic to see if there was a vent or other pipe, but he could not find anything or figure it out. He did, however, load me up with 4 more lbs of freon (two refills in 7 months) and said that it was leaking because the copper in the pipes was being made much thinner these days. He thought the drip might be because it was low in freon. That all sounded bogus to me, but I paid him and let him go, hoping to find a more reliable repair service in future. In any case, the drip is still there after running the unit for 15 mins or so, but goes away after it's off more than 1 hour. I don't think a drip in the wall is a good thing... but I'm not sure how worried I should be...