When a Heat Pump Ices Up: A Warning Sign You Should Never Ignore During Québec Winters
In the heart of Québec’s winter, few things are more frustrating than discovering your wall-mounted or central heat pump completely frozen over, struggling to properly heat your space. While this issue is common, it’s far from harmless—it often signals installation errors, calibration faults, or neglected maintenance. At AirGreen, we frequently respond to emergency calls from homes and buildings across Montréal, Laval, Longueuil, the North Shore, and the South Shore to fix these critical situations. Thanks to our extensive HVAC expertise, we quickly identify the root of the problem—and more importantly, we provide long-lasting solutions that prevent the issue from recurring.
Why Does a Heat Pump Ice Up?
A Climatic Reality… But One You Can Avoid
When temperatures drop below freezing—as they often do in Montréal and surrounding regions—it’s normal for the outdoor heat exchanger to temporarily develop a light frost. However, excessive and persistent ice buildup is a clear sign that the system isn’t functioning properly. The most frequent causes include:
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Poor drainage of condensation under the outdoor unit
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A clogged or defective outdoor fan
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A miscalibrated defrost sensor
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Lack of preventative maintenance
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An improper installation of the wall-mounted or central heat pump
Real Case: AirGreen Intervention in Saint-Eustache, North Shore
One of our clients on the North Shore of Montréal contacted us recently regarding an 18,000 BTU FUJITSU KZAH heat pump that was completely frozen over. Installed two years earlier by another company, the unit had already shown signs of poor automatic defrosting by the second winter.
Our technical team quickly diagnosed the issue: an improperly positioned outdoor sensor and a poorly angled drain line were preventing melted water from draining after each defrost cycle. The result? A thick slab of ice kept growing day after day. We:
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Repositioned and recalibrated the temperature sensor
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Re-leveled the outdoor unit
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Replaced a weakening fan
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Performed a full cleaning of the coils and drain pan
Since our visit, the client hasn’t experienced any more icing issues, and the heat pump now performs at full capacity, even during January’s coldest snaps.
Common Installation Mistakes That Cause Icing
Poorly Leveled Support
The base or metal brackets supporting the outdoor unit must be perfectly level and elevated to prevent the accumulation of frozen water. A unit installed too low or tilting toward the wall leads to water pooling and eventual freezing.
Bad Orientation
If the outdoor unit is positioned facing prevailing winds—especially in exposed areas like the Plateau Mont-Royal or Boucherville—icing can accelerate. At AirGreen, we always aim to install the unit in a way that limits direct exposure to winter gusts.
Missing Wind Breaks or Covers
Sometimes, a simple wind deflector or discreet cover can significantly reduce icing without affecting the unit’s ventilation. We’ve used this solution multiple times in places like Longueuil and Laval, particularly in highly exposed zones.
Neglected Maintenance: The Silent Cause of Icing
A heat pump that hasn’t been maintained will lose efficiency over time. Dust, leaves, or ice buildup block proper airflow, forcing the unit to run longer with less effective defrost cycles. Our HVAC cleaning services in Montréal include:
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Coil washing
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Sensor inspection
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Fan degreasing
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Drain line inspection
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Defrost cycle performance testing
AirGreen Solutions: Our Expertise in Action
We don’t just defrost a unit and walk away: we fix the underlying issue. Here are a few examples of approaches we’ve applied in the field:
In Brossard (South Shore) – Replacing a GREE Temperature Sensor
After noticing that a duplex’s Gree Extreme heat pump was skipping defrost cycles, our technician replaced a faulty outdoor temperature sensor, which instantly improved the system’s operation. We also recommended adding a small wall-mounted wind shield to reduce cold air exposure.
In Laval – Preventive Cleaning and FUJITSU Calibration
In a single-family home in Chomedey, we added a pre-winter HVAC cleaning to the client’s routine. The result? No abnormal icing reported throughout the entire season. Their 24,000 BTU FUJITSU R-32 heat pump now operates at peak efficiency.
What To Do If Your Heat Pump Is Frozen?
Before panicking or trying to chip away the ice manually (which can seriously damage your unit), follow these steps:
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Temporarily turn off the system
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Check the drainage under the unit (is stagnant ice forming?)
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Visually inspect the coils (are they clogged?)
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Call in a specialized team like AirGreen
Why Choose AirGreen to Solve Icing Issues?
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In-depth cold-weather experience: Our installers and technicians understand the unique challenges of the Montréal climate and surrounding regions.
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Long-term solutions: We aim to permanently resolve the issue, not just defrost the unit.
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Personalized advice: Every installation is different. We tailor our recommendations based on your building, usage, and location.
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Annual maintenance service: An AirGreen maintenance contract reduces the risk of winter breakdowns and extends the life of your equipment.
Conclusion: Ice Doesn’t Have to Be Inevitable
A frozen heat pump during winter should never be ignored. By trusting a specialized team like AirGreen, you ensure a fast, accurate, and lasting intervention. Whether you're in Montréal, Laval, Longueuil, the North Shore, or the South Shore, we’re here to maintain your indoor comfort all winter long, without unpleasant surprises.
Noticing ice on your heat pump? Contact us now for a fast diagnosis and expert intervention.