Air Conditioner Freezing Up in Greater Vancouver

An air conditioner with ice forming on the indoor coil or refrigerant lines has an airflow or refrigerant problem — continuing to run a frozen AC causes water damage when the ice melts and reduces system life.

What This Means

The evaporator coil operates below the dew point of the air, collecting moisture as condensate. If coil temperature drops too far below freezing (from low airflow or low refrigerant), moisture freezes on the coil instead of draining — progressively blocking airflow and eventually halting all cooling.

Common Causes

• Filter severely restricted — most common cause of indoor coil icing
• Supply registers partially closed — reduced airflow
• Blower motor running too slowly or failing
• Refrigerant low — low pressure causes the coil to operate colder than rated
• Night operation in cool weather — ambient temperature too low for AC operation (below 15 degrees Celsius)
• Evaporator coil fouled with dust and debris restricting airflow

What Homeowners Can Check Safely

• Turn the AC off and switch to fan-only mode to melt the ice before resuming cooling
• Replace the filter
• Ensure all supply registers are fully open

When to Call a Licensed Technician

Air conditioning and mini-split systems contain refrigerant under pressure and electrical components at line voltage. Do not open refrigerant circuits, attempt to recharge the system, or bypass safety controls — these require a certified technician.

• Refrigerant pressure testing after ice melts
• Blower motor speed testing
• Evaporator coil cleaning if fouled with dust
• Airflow measurement to confirm adequate flow through the system

Frequently Asked Questions

My AC is completely frozen. How long does it take to thaw?

With fan-only mode running (no cooling), a frozen coil typically thaws in 1 to 3 hours depending on how much ice has accumulated. If you turn the system off entirely, thawing can take 4 to 8 hours. Do not run the AC in cooling mode until the ice is completely gone — this causes compressor stress and worsens the icing.

My AC ices up only on certain days. Why?

Intermittent icing is often caused by unusually cool nights. Most residential AC systems should not be operated when outdoor temperatures are below 15 degrees Celsius. On those nights, the refrigerant circuit runs too cold and the coil ices. If icing happens on warm days, refrigerant or airflow is the issue.

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