A service call in the middle of winter on the North Shore
In the middle of January, when temperatures were hovering around -15°C, our AirGreen team received an emergency call from a customer in Boisbriand . Their Mitsubishi wall-mounted heat pump , essential for heating their home, was no longer blowing hot air. In a typical suburban red brick house, the outdoor unit was installed on the back deck, partially exposed to snow. We quickly realized that this was a classic winter breakdown , but one that required a thorough diagnosis to prevent any damage to the compressor.
First observation: a worrying accumulation of ice
On site, our technicians noticed a layer of ice around the bottom of the outdoor unit. This phenomenon, common in winter, may be caused by:
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poor automatic defrosting of the system,
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from a blocked drainage ,
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or a temperature sensor failure .
Despite the presence of fresh snow on the deck, the unit was properly cleared, demonstrating that the customer had taken care to maintain clear access. However, persistent ice on the compressor base and refrigerant lines indicated an incomplete defrost cycle problem .
Step-by-step diagnosis
To determine the exact cause, our AirGreen team followed a rigorous procedure:
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Electrical check : the supply voltage and the main circuit breaker were stable.
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Defrost mode analysis : We observed the behavior of the compressor and fan. The unit entered defrost, but the cycle stopped too early.
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Reading Mitsubishi fault codes : The system displayed a code related to the defrost sensor , indicating an inconsistent measurement.
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Sensor inspection : we noticed a frosted and defective probe , no longer reacting correctly to temperature variations.
Repair carried out: replacement of the defrost sensor
After diagnosing the source of the problem, our technicians proceeded to:
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complete replacement of the faulty defrost sensor ,
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thorough cleaning of the coils and the condensation tray,
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verification of the complete defrost cycle using electronic measuring tools.
Once the new sensor was installed, the Mitsubishi heat pump resumed normal operation: defrosting was effective, and the indoor blowing temperature rose to 28°C after a few minutes.
Technical analysis: the challenges of heat pump heating in winter
Mitsubishi wall-mounted heat pumps are known for their performance in cold climates, but even the most robust models require maintenance adapted to our Quebec winters.
The main causes of winter failure include:
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the frost probe , which prevents the complete defrost cycle,
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blocked drainage , causing frozen water to accumulate under the unit,
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or an improperly calibrated outside temperature sensor .
These elements, although minor individually, can cause the compressor to overheat , reduce energy efficiency and affect the longevity of the appliance.
Restored comfort and preventive maintenance advice
After the repair, we took the time to explain to the customer good winter maintenance practices:
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Clear snow around the unit after each storm.
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Check for ice under the base of the unit at least once a week.
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Schedule preventative maintenance with AirGreen in the fall to inspect sensors and drains before the heating season.
Thanks to this rapid intervention, the customer regained stable comfort in his Boisbriand home and avoided a more serious breakdown that could damage the compressor.
Why choose AirGreen for your heat pump repairs in Montreal and on the North Shore
At AirGreen , we understand the demands of the Quebec climate and the challenges that extreme temperatures pose for wall-mounted HVAC systems.
Our advantages:
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Certified technicians specializing in brands such as Mitsubishi, Fujitsu, Gree and Midea.
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Rapid interventions , even during peak winter periods.
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Original parts and guaranteed repairs.
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Transparent customer service : detailed explanation of repairs carried out.
Our mission: to offer every household in Montreal, Laval, Longueuil, the North Shore and the South Shore a reliable, efficient and sustainable service.
In conclusion: an AirGreen service that lives up to Quebec winters
This Mitsubishi wall-mounted heat pump repair in Boisbriand once again demonstrates the importance of professional diagnosis and regular maintenance . By replacing a simple sensor, we've brought a vital system back to life for home comfort in the middle of winter.
At AirGreen, we remain available for any HVAC service call , whether for a breakdown, maintenance or a complete installation.
Your comfort is our priority — all year round, in all weather.