The diagnosis does sound rational but does need confirmed with pressure gauges and thermometers to verity if it is low. But I believe in checking other simple and overlooked reasons before condemning a unit as having a leak before pulling out the gauges to even check.

There are other issues which would simulate the same effects of a dirty filter. To many blocked or shut supply vents, blocked return grills, blower motor not running or a very dirty caked up squirrel cage fan will lower air movement over the evaporator in the house will do the same as a dirty air filter.

Setting your thermostat to low will also cause the evaporator to freeze up and migrate to the condensing unit. Any chance you set it below 67 degrees? It would take a while to move to condenser but once the evaporator starts freezing over it turns into a domino effect. If this was the case and once it thawed out it would be fine unless you did it again.

A restricted metering valve is least common but would also cause your condensing unit to freeze up. This is often overlooked and has cost many a new condensing unit only to find the tech never checked the super heat. If he didn't investigate any of the other reasons I mentioned and automatically assumed it's low refrigerant I'd be suspect. Over confident is just as dangerous as under qualified.

You need to go to the air handler and see if the fan is actually working. If it is and the first time there was no air it means the evaporator in the air handler was completely blocked with ice.

The 2nd time you check and found some air blowing the ice has started to melt. You will be able to hear the fan running at the air handler if it is running. If it's running keep it on "ON" to melt the ice. You did good turning it on, but do not turn on the air conditioning.

Thank you. I think I'm getting my terms mixed up. So when I said the fan was not working I'm talking about the big fan blade looking thing in the unit outside. That's not turning on when I turn the fan on, on the thermostat. But even when I have the thermostat set completely off (system and fan both off), air is coming up through the vents. How/why is it coming up if I have the system off?

This thing. Should this be spinning when I turn the fan on, on the thermostat? It's not spinning at all, but air is coming up through the vents, but it's coming up through the vents even when I turn the whole system off as well. I've noticed the majority of ice seems to have melted away from what I can see.

Hi, I don't know much about air conditioners. If you have a furnace that is your air handler. The fan switch on your thermostat probably has an auto or an on switch but no off. When you turn it on air comes out of the ducts

The fan out side only comes on when the compressor is running.

Good Luck Woodbutcher

Don't let this guy replace your coil until he has identified that this is where the leak is (and if he doesn't know how to do this, find someone else).

I'm in SC where the temps are up and down, so the temp has dropped drastically again last night and is now back in the 30s (from the high 70s/80s two days ago). I've had the unit off all night except for the fan. Am I able to turn the heat back on, or should I leave the entire unit off?

You should have an "emergency heat" setting on your thermostat. Turn that on. It will cost more but is the accepted temporary procedure until you can get the issue resolved.

Did they come back to repair it?

The fan control on the thermostat is for the fan inside. The fan outside turns on when it's in air conditioning or heat pump mode.