A/C unit was running, but noticed no air was coming out of the vents. Went in the basement and found the A-coil was a solid block of frost and ice. What causes this? It ran fine all of the weekend when it was very hot out. Only difference today is that a thunderstorm passed through and it is very humid outside. The ice goes from the A-coil and entire insulated line all of the way outside and to the compresser. Could this be as simple as the A-coil needing to be cleaned? Here is a pic, hope it shows up well on this post.