Why is my AC freezing up

Your AC is likely freezing up due to restricted airflow, low refrigerant, or a dirty evaporator coil. When warm air can't flow properly over the cold evaporator coil, ice forms and blocks the system from cooling your home effectively.

Restricted airflow is the most common culprit. A clogged air filter forces your system to work harder and reduces warm air circulation over the coil. Check your filter first - if it's dirty or hasn't been changed in months, replace it immediately and let the ice melt completely before restarting. Other airflow issues include blocked return vents, closed supply registers, or a failing blower motor.

Low refrigerant levels from a leak will also cause freezing. When refrigerant is low, the remaining refrigerant gets too cold as it expands, causing ice buildup on the coil. This requires professional repair since handling refrigerant requires certification, and the leak must be found and sealed before recharging the system.

Dirty evaporator coils can't absorb heat properly, leading to ice formation. The coil may need professional cleaning if it's heavily soiled. Other causes include a malfunctioning thermostat, damaged ductwork, or a failing expansion valve.

In Ottawa's climate, frozen AC units are particularly problematic during our humid summers when you need cooling most. Never run your AC with ice on it - this can damage the compressor, leading to expensive repairs ($800-$2,000+). Turn off the system, switch the fan to "on" to help melting, and wait for all ice to disappear before restarting.

If the problem persists after changing the filter, you'll need professional diagnosis. Refrigerant leaks, coil cleaning, and component repairs require licensed technicians. For persistent freezing issues or refrigerant problems, request a diagnostic service call to identify the root cause and prevent compressor damage.

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