Frozen Evaporator Coil
A frozen coil in a Dallas home almost always starts with airflow, and the single most common trigger we find is a filter left in far too long through the heavy summer runtime - starve the coil of warm air and it drops below freezing and ices over.
Two paths lead to that ice. If the filter is clogged, vents are closed, or the blower is weak - and the system has been running hard - it's an airflow problem: too little warm air crosses the coil, so it gets cold enough to frost. If the filter is clean and it still freezes, particularly after weeks of gradually weaker cooling, the trail leads to refrigerant instead - a charge that's leaked low drops the coil's pressure and temperature until it ices. Which path it is decides everything that follows.
The airflow version is usually the cheap fix - a fresh filter, an opened return, a blower repair. The refrigerant version is the one with weight behind it: the leak has to be located and sealed before a recharge, and if your system runs R-22 that no longer makes economic sense past a certain age, given how scarce and costly that refrigerant has become. There's also a hidden cost to letting it freeze repeatedly - running the compressor while liquid refrigerant floods back to it can damage the priciest part in the system.
Dallas summers set coils up to freeze. Months of near-constant runtime clog filters quickly, and all the construction dust in the fast-growing suburbs - Frisco, McKinney, Prosper - loads them faster still. Homeowners fighting 105-degree afternoons often crank the setpoint unusually low, which pushes a marginal system past the freezing point. And when the ice finally melts, it dumps water into an already-hot attic, so a frozen coil and a ceiling stain frequently arrive together.
How we pin it down
- Shut off cooling and run the fan to thaw the ice safely
- Inspect and replace the filter, and check the return is sized right
- Verify blower speed and operation
- Check the evaporator coil for dirt limiting heat transfer
- Read the refrigerant charge and look for a leak
- Confirm proper airflow before returning the system to cooling
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Frequently asked questions
It's 105 outside - how is my coil turning to ice?
It feels backward, but freezing is about the coil getting too cold, not the weather being cold. Choke the warm airflow across it - with a dirty filter or low blower - or drop its pressure with a low refrigerant charge, and the coil falls below freezing and frosts over even on the hottest day. The harder it runs in the heat, the faster a restricted coil ices up.
I replaced the filter and it froze again - now what?
If a fresh filter didn't hold, the restriction is deeper - a dirty coil or a failing blower - or the cause isn't airflow at all but a low refrigerant charge from a leak. That second one won't fix itself, and it keeps re-freezing until the leak is repaired. At that point a proper diagnosis with gauges is what stops the cycle.
Could a refrigerant leak be behind the freezing, and is that expensive?
It's one of the two main causes, and yes, it's the costlier one. A sealed system doesn't lose refrigerant on its own, so a low charge means a leak that has to be found and sealed, then recharged. On an older R-22 unit the refrigerant is scarce enough that we'll walk you through whether the repair or a replacement makes better sense for your situation.
Am I making it freeze by setting the thermostat really low?
You can push a marginal system over the edge that way. Setting the temperature very low against a 100-plus afternoon makes the coil run colder for longer, and on a system that's already a little restricted or low on charge, that's often enough to tip it into freezing. Fixing the underlying restriction matters more than the setting, but easing off the extreme lows helps while you wait.
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