I have a 2 story home and the AC unit for the bottom floor is not working properly. Unit is running outside, but no air period is coming out of the vents. I went into the crawlspace and nothing is blocking the duct work. I opened the panel on the side of the AC unit and the coil has frost on it. I don't think it is frozen. I turned the unit off for about 20 minutes and when I started it back up, I noticed the frost on the coils was very distinct. But there wasn't any air being circulated into the duct. Not sure what is going on...