Frozen Evaporator Coil
Ice on the indoor coil or the copper lines calls for one immediate move: switch the system off cooling and let it thaw. This is the rare case where continuing to run the AC does real harm - pushing liquid refrigerant back to the compressor while the coil is frozen can cause the most expensive failure in the whole system. So the decision is made for you: shut off cooling, then find out why it iced up.
While it thaws, gather the clues in order. Pull the air filter - if it's gray and packed, restricted airflow is the likeliest reason the coil dropped below freezing, and a fresh filter is step one. Walk the house and open any closed or blocked supply vents and returns; starving the coil of warm return air freezes it. Set the thermostat to off for cooling but turn the fan to "on," which runs the blower to melt the ice faster. Once it's thawed, look at the copper lines for an oily residue, a telltale sign of a refrigerant leak. Don't restart cooling until the ice is completely gone.
Restricted airflow is the most common trigger by far, and a dirty filter leads that category - in plenty of homes a neglected filter is the entire cause. Blocked vents, a dirty blower wheel, and a caked evaporator coil follow close behind, all choking the airflow the coil needs. Low refrigerant is the other major cause: a leak drops the coil's pressure and temperature until it ices over, so a frozen coil frequently points straight at a leak. A weak or failing blower motor that can't move enough air rounds out the usual suspects.
Two Central Florida realities gang up on your coil. First, humidity: there's so much moisture in Orlando air that any airflow or charge problem frosts the coil quickly, because there's endless water to freeze onto it. Second, oak pollen: our heavy spring pollen mats onto filters and coils, throttling airflow right as the cooling season ramps up, so late-spring freeze-ups are common. Run that combination close to year-round with little downtime, and a coil that's slightly short on airflow rarely gets a chance to recover before it locks up in ice.
What we do on arrival
- Confirm cooling is off and let the coil thaw completely before testing
- Replace the air filter and check the return for restriction
- Inspect the evaporator coil and blower wheel for dirt limiting airflow
- Test blower motor speed and the airflow moving across the coil
- Measure refrigerant pressures and search for a leak if the charge is low
- Check the condensate drainage that the thawing coil overwhelmed
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Frequently asked questions
Can I just let it thaw and go back to using it?
You can get cooling back for a while, but the ice will return if the cause isn't fixed. Freezing means either restricted airflow or low refrigerant, and if a fresh filter doesn't solve it, something deeper is driving it. Running it in a freeze-thaw cycle stresses the compressor, so it's worth diagnosing instead of repeating.
Does a frozen coil mean I have a refrigerant leak?
It might. Low refrigerant is one of the two main causes of a frozen coil. Refrigerant doesn't get consumed the way fuel does, so if the charge is low, it escaped through a leak that has to be found and sealed. We rule out airflow first - filter, vents, blower - and if those are fine, we test the charge and hunt for the leak.
Is it safe to keep cooling while it thaws so I stay comfortable?
No - that's the one thing to avoid. Cooling a frozen coil can send liquid refrigerant back to the compressor and damage it. Switch cooling off and set the fan to "on" so the blower melts the ice; you'll be without cold air for a few hours, but you'll protect the costliest part in the system.
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