Why your air conditioner keeps freezing up
An air conditioner freezes when the evaporator coil drops below freezing, which happens when airflow drops too low or refrigerant pressure falls. A clogged filter is the most common culprit, though blocked vents and a dirty coil can produce the same result. A refrigerant leak is the other main cause, and that one requires a licensed technician to fix.
Why does an air conditioner freeze up?
The evaporator coil inside your AC gets cold by absorbing heat from the air moving across it.
That exchange is what keeps the coil from dropping below freezing. Cut off the airflow, or reduce the refrigerant pressure, and the coil gets so cold that moisture in the air turns to ice on contact. A clogged filter is the most common cause: it starves the coil of the warm air it needs. Blocked or closed vents do the same thing in specific rooms or zones. A dirty evaporator coil insulates itself, so heat transfer slows even when airflow is fine. Low refrigerant drops the pressure inside the coil and produces the same result. Freezing is a symptom of something the system is being denied, and in many cases that something is as simple as a filter that has not been changed or a vent that has been pushed shut.
Why does my AC keep freezing up?
Start with the system off.
A frozen coil has to thaw completely before anything else you do will matter, so shut the unit down and give it time. While it thaws, pull the filter. If it is clogged with dust, swap it for a clean one. Walk the house and check that every return vent is unobstructed and every register is open. Those are the steps you own. If the coil freezes again after a clean filter and open vents throughout the house, the cause is somewhere the homeowner cannot reach. A refrigerant leak will starve the coil of the heat exchange it needs to stay clear. A failing component inside the air handler can produce the same result. Both require instruments to diagnose, and refrigerant work requires a licensed technician by law.
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