ski

cut your system off.

Usual cause is freon leak but also could include poor air flow due to dirty filter and/or clogged evap coil.

IMO

Under charged,or over charged.

Overcharge?!!! Hmmmmm, explain please,,,,thanx.

Had much the same scenerio icing of line and coil, with no virtually no air coming thru vents - technician tried adding Freon first - no change. Then was going to replace blower motor, but meanwhile, I checked the inside coil on my heat pump, and found it covered with 19 years of dirt and dust. So after he removed that crap, I had air! Virtually no air was getting through it. So, I would say tigerdunes post above is right on.

Mr HAVAC. You are not serious are you ? An over charged system brings liquid back to the compressor. I've accidentally over charged many a unit and had ice on the
return line. the poster said " lines " and never meant the
liquid line. I've under charged many a unit and had ice on the return line. Under charge an A.C. on a car and the suction line freezes solid. Over charge it and it will sweat. That is before the pressure relief valve blows and that only happends on high R.P.M. Until then the line will freeze.

Mr HAVAC. You are not serious are you ? Yes I am K. When you overcharge a system the liquid backs up into the condenser. This reduces the amount of condenser surface so the head pressure and condensing temperature goes way up. When your head pressure goes up your suction follows, correct? So how can you flood back when you have such high suction pressure? If you were bringing back liquid wjen you supposedly over charged something else was wrong with that system, the most common culprit would be the TXV.

Mr. HAVAC. Next time you have a few extra bucks pop over and i'll over charge my A.C. system for you, mine has a cap tube. We can both watch the suction line freeze back to
the compressor. I'll have to shut her down just as the
compressor bangs liquid. Gets a little scary.Actually i can just shut off the furnace fan and get the same result. trust me. I've accidentally over charged many a unit before i got into school and learned to take my time and not see how many units i could do in a day. actually the freeze back works best with a wall shaker. It could be fun arguing over the same right answer. I remenber one very hot day on the roof of a church, so hot you couldn't touch
your tools after 10 minutes. We would sit inside the roof top and shut down the evap. fan to stay cool but had to be very carefull to turn the fan back on as the ice worked it's way back to the compressor. F.Y.I. the ice moves about 1 inch a minuet on a 4 inch suction line. The evap.
fan was 17 H.P. so you did not want to be inside with it
running. Take care. Have a good week.

"Actually i can just shut off the furnace fan and get the same result. trust me. "
Well there you go, thats the reason for icing back. By shutting off the fan you've totally removed the load from the evaporator. And if you're seeing the suction line ice back on a window unit that means you have the outer jacket off and if you have that off then the blower is not pulling air across the evap coil. Nothing to do with overcharging.