First post here- Ok so I purchased a Lennox XC21 a little over 2 years ok. It has a 20x20x5 filter and a UV lamp and neither has been replaced since the install, not sure if that is the issue but wanted to let you know. So here is the situation last night we noticed that the house seemed warm. I went over to the thermostat and the temperature read 80 degrees but said cooling on it. It is always set at 77 so the air should have kicked on but it hadn't. I went outside and the condenser was running as normal but I did notice that the drip line coming out of the house had no water coming out of it. I then went to the air handler inside and it was running but very lightly not nearly as load as if the house was in the actual "cooling stage". I shut off the unit from the thermostate for about 5 minutes then turned it back on. The air kicked and started cooling fine the drip line had water coming out of it as normal. Well about 30min later it did the same thing the air stopped and the temp raised to 80 degrees again. This time I removed the panel in the handler and noticed that the drum of the fan had evaporation on it with what looked to be water droplets coming off the bottom dripping onto the coil box below it. Looking further at the coil box I noticed that the left side of it was fine but the right side had a tint of white to it. I touched it and it had a layer of frost on it not thick though but definately cold and white. I shut the unit down again for about 50min thinking in might need to thaw? No such it was still doing the same thing no air coming out of our vents and the handler is not running as it should be. I shut it down for the night and hoped this morning it would work but nothing same issues. Anyone have any input on this issue? Would it be related to the filter or uv lamp? I also tried removing the filter in case it was clogged and was stopping it from working but that did not solve the issue. Does the filter have to be in it to work? Any help on this would be greatly appreciated. I am at a loss and am dreading calling to get this serviced if it is something I can do to get it working. Thanks very much!