An air conditioner freezes when the indoor coil gets colder than it should, and that happens for two reasons: not enough warm air moving across the coil, or not enough refrigerant in the system. Restricted airflow is far more common and often self-inflicted through a dirty filter or closed vents. Low refrigerant means a leak, because a sealed system does not consume refrigerant.
What should you do the moment you see ice?
Turn the cooling off but leave the fan running. Running the compressor against a frozen coil can damage it, while the fan alone will thaw the ice in a few hours. Put towels down: melting ice has to go somewhere.
Do not chip the ice off. You will puncture the coil, and a coil leak turns a cheap visit into an expensive one.
How do you tell airflow from refrigerant?
Airflow problems usually show ice on the indoor coil and a filter you can no longer see through. Refrigerant problems usually show ice starting at the outdoor line where it enters the unit, along with cooling that got gradually weaker over a season rather than suddenly.
A leak is the important distinction. Topping up refrigerant without finding the leak means paying for the same repair again next summer, and venting refrigerant is a regulated matter in Canada.
What prevents it happening again?
Most repeat freeze-ups we see come back to airflow the system never had. Undersized return ducts, a filter thicker than the system was designed for, or closed vents in unused rooms all starve the coil.
- Change filters on schedule, and use the thickness the system was designed for
- Keep supply and return vents open, including in rooms you do not use
- Have the indoor coil cleaned if the system is more than a few years old
- Fix leaks properly rather than topping up refrigerant each season
We fabricate ductwork in our own Maple Ridge shop, so when a freeze-up traces back to a return that was never big enough, we can fix the cause instead of recharging the system every June.
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We will find why it froze, not just thaw it and refill it.