I changed the motor on one of them the other day, at first it wasn't cold, I was told it takes awhile, then the next day, it started getting cold, but now its blowing warm air. And now the downstairs unit has decided to quit blowing air altogether. I noticed a frost on the copper tubing outside, so this morning I turned the fan to the "on" position to see if it was frozen and I could defrost it, but there is no air blowing out of the vents. Could you suggest anything for this problem?