A frosted unit on a brick wall: AirGreen's precise diagnosis
At AirGreen , we often receive calls in the winter for completely frozen outdoor units . This was the case in Sainte-Rose (Laval) , where a customer contacted us after noticing that his Midea wall-mounted heat pump was no longer heating properly and that ice had formed on the side of the condenser.
Upon our arrival, our technicians noticed significant icing on the outdoor evaporator , visible through the protective grille. This type of symptom almost always indicates a defrosting problem – a cycle essential to the proper functioning of a heat pump during Quebec's cold months.
Diagnosis: Understanding the cause of icing
After securing the unit, we performed a full system analysis :
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Checking the automatic defrost mode : the system did not trigger the complete cycle.
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Outdoor temperature sensor test (defrost probe) : slightly dirty and out of calibration.
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Fan and coil inspection : no major obstructions, but frost buildup had slowed ventilation.
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Compressor current measurement : stable, indicating that the compressor was working correctly.
Diagnostics revealed that the defrost sensor (thermistor) was the root cause. With an incorrect reading of the outside temperature, the system remained stuck in a continuous heating cycle, without switching to defrost mode.
Repair: Defrost cycle overhaul
Our technicians have:
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Replaced the faulty defrost sensor with a genuine Midea part.
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Cleaned the coil with a biodegradable product specially designed for heat pumps to remove the thin film of frozen dust.
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Checked the correct operation of the automatic defrost using our temperature simulator.
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Readjusted the fan airflow for better frost removal in the future.
Everything took place in less than two hours, and the heat pump was able to resume optimal operation immediately.
Result: comfort regained and efficiency restored
Once the repair was completed, the customer immediately noticed that warm air was once again circulating efficiently throughout the house. The defrost cycle now automatically kicked in every 40 to 60 minutes depending on the outside temperature—exactly as the manufacturer intended.
We also installed a snow shield above the outdoor unit to prevent melted snow from freezing on the coil, a simple but essential measure to extend the life of the heat pump.
AirGreen Tips for Preventing Frost on a Wall-Mounted Heat Pump
A frozen unit isn't always a sign of breakdown, but it's a warning sign that shouldn't be ignored . Here are some recommendations we share with our customers across Montreal, Laval, the North Shore, and the South Shore:
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Maintain a minimum clearance of 12 inches around the outdoor unit.
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Clean the grilles and coils regularly using a gentle jet of water.
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Check defrost cycles by observing if the fan stops temporarily to defrost.
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Install a sturdy wall bracket to prevent vibrations and facilitate the flow of defrost water.
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Schedule an annual professional interview before the cold season.
Local expertise: AirGreen, trusted partner in Sainte-Rose and throughout Laval
In Sainte-Rose , as in Chomedey, Sainte-Dorothée or Fabreville , our technicians know the extreme winter conditions of Quebec and adapt each intervention to the local reality:
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Variable temperatures below zero,
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High humidity near the Mille-Îles River,
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And frequent freeze/thaw cycles.
Thanks to our experience with Midea, Gree, Sharp, Fujitsu and Goodman heat pumps , we offer durable and guaranteed repairs that restore performance and peace of mind to our residential customers.
In summary
The intervention in Sainte-Rose demonstrated the importance of accurate diagnosis and regular maintenance of HVAC systems . At AirGreen , we don't just repair: we optimize the energy performance of each device to extend its lifespan and improve the comfort of our customers, whether in Montreal, Laval, Longueuil, on the North Shore or the South Shore .