Common HVAC Problem
Why Is My AC Freezing Up?
Ice on your AC unit is a sign something is wrong with airflow or refrigerant levels. This problem gets thousands of searches every month — and it's usually one of four causes.
Common Reasons
What causes an AC to freeze up?
A frozen AC might seem counterintuitive in the middle of summer, but it's actually very common. Here's what's happening inside your system.
Dirty Air Filter
A clogged filter restricts airflow over the evaporator coil. Without enough warm air passing over it, the coil temperature drops below freezing and ice starts to form. This is the #1 cause — and the easiest to fix yourself.
Blocked Airflow
Closed vents, furniture blocking returns, or a collapsed duct can all starve the system of airflow. The result is the same as a dirty filter: the coil gets too cold and freezes. Check that all vents and returns are open and unobstructed.
Refrigerant Leak
Low refrigerant causes the pressure inside the evaporator coil to drop, which makes it abnormally cold. Ice forms on the coil and refrigerant lines. You might hear a hissing sound near the outdoor unit. This requires a professional.
Blower Motor Problem
If the blower motor is weak, failing, or has stopped entirely, air can't circulate over the coil. Even with a clean filter and open vents, a bad blower means no airflow — and that leads to freezing.
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