I hate when it too hot out there and your ac freezing up. It can be quite troublesome especially in the summers. Your ac could be freezing because of many reasons. Sometimes you can treat it yourself and sometimes you’ll need to call a technician.

So In this article, I’ll list all the 8 possible reasons why your air conditioner is freezing up. I’ll also provide their DIY solution if possible otherwise you’ll have to call a technician. 

Reason No #1: Your Furnace Filter Is Dirty

The first reason why your ac is freezing up is because of the very dirty furnace filter. If you don’t remember when was the last time you changed or cleaned your filter then my friend that filter is causing the problem. Over time your filter gets clogged up by dirt and debris and it loses its filtering power. 

Also if you're doing any kind of construction work, any woodcutting, or even painting. The dust produced from that will get sucked in by the return air and plug up your filter real quick.

And when your filter gets really dirty there's not enough airflow going through the evaporator coil which causes the temperature of the refrigerant to drop. And slowly that evaporator coil will start to frost up and then build up ice.

So the condensation that's running down your coil and going down that condensate drain will also start to freeze up and the longer you run it the more it'll freeze.

And eventually, the freon line set going outside will start to frost up as well. And If you've been running your ac for a long time then the components of the condenser unit will also start to freeze up.

Especially in the areas where there's no insulation and if you look inside the compressor it will be just a big block of ice. 

So you have to change your furnace filter at a regular period like every month or two. And this will keep your ac running smoothly.   

Reason No #2: You have Too Many Closed Vents

The second reason why your AC could be freezing up is if you have too many vents closed off or even worse if you have some of your return grills closed off. 

So maybe you were moving around some furniture and you put a couch or other thing in front of a return grill. So my friend that will yield you similar results as having a plugged filter.

So if your AC is freezing up one thing you can try doing is opening up all your vents and making sure that all your return grills are opened up as well.

And I have seen this before where the customer would think that the big return grill is actually a register or a vent from where the cold air blows out.

But return grills do not have shut-offs so what they would do just put some kind of paper over it or some cardboard and tape it up and of course in a couple of days there AC freezes over. So make sure you have all the return vents or grills opened up.

Reason No #3: Your AC Unit is Low on Refrigerant

Another common reason why your AC is freezing up is that the unit is low on refrigerant or low on freon. The way it works is the temperature of the freon that's going inside in the evaporator coil is about 38 degrees.

And when you're low on freon pressure the temperature will go down. Because pressure and temperature correlate which means if one goes up the other goes up and if one goes down two other goes down.

Once the freon pressure gets below 32 degrees the condensation that your evaporator coil is collecting is going to start freezing over.

And again the longer you run it the more ice will build upon the A-coil and eventually the ice will travel outside to the compressor as well. 

Now if you've noticed that your AC unit has frozen over like that there's no point to continue running it because it's not doing much cooling and all it's doing is building up more ice.

So In that case I would turn off the air conditioner and turn your fan setting on from the thermostat and keep that furnace fan on for a while.

And it'll take sometimes a day or even two depending on how much ice you have built up there. And once the ice starts melting keep in mind that the ice will not always go neatly down into the drain pan.

It’ll go down the sides of your furnace and inside of your furnace. I highly recommend that you should put down some towels and be expecting that there will be a little puddle underneath your furnace. 

Now talking about the solution unfortunately freon issues are not exactly a DIY kind of project. You’ll need to call a technician for the freon refill.

Reason No #4: Your Thermostat Setting Is Too Low

Another reason why your ac is freezing up is if you're setting your thermostat too low. The lowest set point that most air conditioners are designed for is about 67 degrees.

So if you're setting your air conditioner to like 61-62 for some reason. So there's a good chance that your air conditioner will start to freeze up. The lowest you should go on the thermostat is about 67- 68.

I have a full tutorial on How you can bypass your thermostat if it's not working

Reason No #5: Furnace Blower Motor Not Working 

Another reason why your AC could be freezing up is that your furnace blower motor is not working. The blower motor could be burnt out or maybe the capacitor for it is either weak or dead.

If that blower motor is not spinning and there's no air going across that evaporator coil it will freeze up in minutes. And of course the longer you keep the outside unit running without the fan inside running the more ice will build upon that thing.

And many times if your motor inside the furnace is trying to start but it's failing because either the bearings are burnt out or the windings are opened.

If you take out the bottom doors of the furnace and just reach in there and carefully touch the motor it'll most likely be really hot to the touch. If it is really hot then there's a good chance that that motor is burnt out.

So the solution for this problem is you have to replace the blower motor if it’s burned and if the capacitor is dead then you can change it yourself at home. I have a tutorial for that do check it out.

Reason No #6: You Have A Bad Control Board

Another thing that I see once in a while is that the actual control board will be bad inside the furnace. So the board is simply not sending power to the blower motor therefore it is not turning on and blowing air.

And since the blower motor is not turning on your unit will freeze up. Honestly speaking control boards are not that easy to repair or troubleshoot. You’ll need to call a technician for that.

Reason No #7: Clogged Metering Device 

Another reason why your air conditioner could be freezing up is if your metering device which is at the evaporator coil is plugged up. Usually, it'll either be a TXV metering device or a fixed metering, or a piston.

And how that could happen is if you have some kind of a contaminant inside of your freon loop. That metering device is actually just a really small tiny hole so it will not take much to get that thing plugged up.

And if there is some kind of blockage blocking that metering device and the freon is having a hard time going through that will lower the pressure inside of that evaporator coil.

And if you remember how I mentioned earlier the lower pressures equal lower temperatures and once again that would cause your evaporator coil to freeze up. And unfortunately, this too is not exactly a DIY type of project. You probably will have to call a technician to figure that one out for you.

Reason No #8: Plugged Up Evaporator Coil

The last reason, why your AC could be freezing up, is if the evaporator coil is plugged up. This coil is located at the furnace. If your evaporator coil is plugged up let's say you forgot to put in a filter at one point or your filters are dirty often.

Whatever dust gets by that filter will go up and get settled into that evaporator coil. The evaporator coil is almost like a little radiator with fins.

So if there's a lot of dust that gets under there it will start to block the bottom of that which will also restrict the airflow causing the same freezing effect.

Cleaning an evaporator coil is tough and you’ll need to call a duct cleaning company for that. Generally, most duct cleaning companies will not clean your E-coil unless you specifically ask for it.