When winter cold puts wall-mounted heat pumps to the test
At AirGreen , we know that a well-maintained wall-mounted heat pump is essential for weathering Montreal 's winters. Our team recently worked in Saint-Léonard , a residential neighborhood where red brick homes are often equipped with Fujitsu wall-mounted systems, which are known for their efficiency but are susceptible to poorly regulated defrost cycles.
Our customer contacted us after noticing that their Fujitsu heat pump was no longer heating properly despite still-moderate temperatures. The indoor fan was running, but no heat was being emitted . The outdoor unit, mounted about two meters above the ground, seemed to be permanently frozen—a clear sign of an automatic defrost problem .
Diagnosis: a faulty outdoor temperature sensor
Upon arrival, we noticed that the Fujitsu wall-mounted condenser , exposed to wind and humidity, had accumulated a significant layer of ice around the coil. This prevented the heat pump from performing an effective defrost cycle.
After securing the installation on the ladder and removing the top cover, our technician undertook a series of checks:
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Defrost sensor (thermistor) continuity test : inconsistent values.
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Main electronic board check : in order.
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R-410A refrigeration pressure control : stable, no leaks detected.
The diagnosis was clear: the outside temperature sensor was transmitting incorrect information to the card, causing the defrost cycle to block.
Intervention: sensor replacement and unit refurbishment
We replaced the original Fujitsu defrost sensor , carefully positioned on the coil according to the manufacturer's specifications. After re-energizing:
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The defrost cycle has started automatically .
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The compressor has resumed its normal heating sequence.
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The indoor temperature began to gradually rise, reaching 22°C in less than 30 minutes.
We then carried out a complete cleaning of the external exchanger , removing all residual ice and ensuring that the condensate drainage was carried out without obstruction.
Prevention: tips for a breakdown-free winter
To avoid this type of problem, we recommended to the customer:
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Complete preventative maintenance before winter , including testing of sensors and the electronic card.
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Regular cleaning of the condenser fins to ensure good heat exchange.
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The installation of a protective roof above the condenser , limiting the formation of ice by direct precipitation.
These simple actions can significantly extend the lifespan of a Fujitsu wall-mounted heat pump and maintain its energy efficiency, even during the extreme cold of the North Shore and South Shore .
Result: restored comfort and a satisfied customer
By the end of our intervention, the Fujitsu heat pump was working perfectly. The defrost cycle was running at regular intervals, the hot air flow was stable, and the power consumption had returned to normal.
The client, relieved to be able to regain warmth in his living room without resorting to additional heating, also told us of his intention to add annual AirGreen maintenance to his residential schedule.
AirGreen expertise at the service of reliability
Every winter, our team performs hundreds of similar HVAC repairs across Montreal, Laval, Longueuil , the North Shore , and the South Shore . Our Fujitsu, Gree, Sharp, Midea, Goodman, and other major brand certified technicians respond quickly, using genuine parts and state-of-the-art diagnostic tools.
Our commitment is simple: to restore performance, extend lifespan and ensure lasting comfort for our customers .