Of all the calls we get once the heat sets in, this is the one that confuses people the most: it's 95 degrees out, the house won't cool, and they walk outside to find their air conditioner wrapped in ice. It feels backwards. How does anything freeze in the middle of a Treasure Valley summer? Why is there ice on the unit, but my house is 85 degrees inside? It's actually one of the more common problems we see this time of year, and the cause is usually simpler than you'd think. Here's what's happening, and what to do about it.
Why is my AC freezing up in the middle of summer?
Almost every time, it comes down to one of two things: not enough airflow over the coil, or low refrigerant.
Your AC has an indoor coil that gets cold to pull heat out of the air, and it's supposed to stay just above freezing. But if warm air from your house stops flowing across it, usually because of a dirty filter or blocked vents, the coil keeps getting colder with nothing to warm it back up, and the moisture on it freezes. Once a little ice forms, it blocks airflow even more, and the whole thing snowballs into the frozen mess you're looking at. That ice block just keeps getting bigger and bigger until it's big enough to make snow cones out of.
The other common cause is low refrigerant, usually from a small leak. Less refrigerant means lower pressure, which drops the coil temperature below freezing. That one isn't a DIY fix unfortunately, read more on that below.
What should I do the second I notice ice?
Step one is to always turn it off. Don't keep running it.
Switch your thermostat to "off" for cooling, but flip the fan to "on". Running the fan with the cooling off blows household air across the coil and melts the ice faster. A fully frozen system can take several hours to thaw, sometimes the better part of a day. We know that's miserable timing in a heat wave, but running a frozen AC doesn't cool your house, and it can wreck your compressor, the single most expensive part to replace. Patience here genuinely saves you money and will get you cooling again quicker.
One thing not to do: don't chip at the ice to speed it up. The coil and refrigerant lines damage easily, and a punctured line turns a free fix into a big one. We've seen too many people try to hack at this with a hammer only to cause real damage and need a full coil replacement.
Can I fix it myself?
If it's an airflow problem, probably.
While it thaws, do these three things:
- Check your filter. If it's dirty, replace it. This is the number one cause, and it's only going to cost you $10-$20 and 5 minutes to do it yourself.
- Open up your vents, make sure none are blocked by furniture or rugs, and check that your return grilles are clear. The system needs to be able to breathe.
- Once it's fully thawed and you've got a clean filter, turn the cooling back on and watch it. If it runs normally and doesn't ice back up, you fixed it.
When do I need to call someone?
If it freezes up again after a full thaw and a fresh filter, airflow isn't your problem. It usually points to low refrigerant or a coil that needs cleaning. Refrigerant work is licensed for a reason: a system that's low is leaking somewhere, and just "topping it off" without finding the leak is throwing money at a problem that comes right back. Topping off a system is like trying to fill a bucket with water when the bucket has a couple holes in it.
Call us if you notice water pooling around your furnace or air handler from all the melted ice, if the system ices up fast every time, or if you're simply not comfortable poking around. The big thing we want you to take away is that we don't keep running it frozen and hope it works itself out. That's how a cheap fix becomes a compressor.
The short version
Ice on your AC almost always means airflow or refrigerant. Shut the cooling off, run the fan to thaw it out, change your filter, and clear your vents. If it freezes again after that, it's time to call a professional. Whatever you do, don't run it iced up, because the compressor is the part you really don't want to be replacing in July.
Stay cool out there. We're a family-run shop covering Nampa, Caldwell, Meridian, Boise, and beyond. 208-455-5158.