An urgent service call in the heart of Montreal winter
On a cold winter day, our AirGreen team was called to Montreal's LaSalle neighborhood to address a problem with a Mitsubishi Electric wall-mounted heat pump installed on the exterior wall of a duplex. The concerned owner had noticed that the outdoor unit was no longer producing heat and that unusual frost was accumulating on the coils despite a recent defrost.
At AirGreen , we know that in these kinds of situations, every minute counts: a broken HVAC system in the middle of winter can quickly compromise the comfort of a home, especially when the temperature drops below zero.
Diagnosis: A defrosting and drainage problem
Upon our arrival, our certified technicians performed a complete inspection of the Mitsubishi Electric wall-mounted heat pump model MUZ-GE12NA . The compressor started, but the air blown inside remained lukewarm.
Here's what our team observed:
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A thick layer of ice had formed on the bottom of the outdoor unit, restricting airflow.
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The condensate drain was partially blocked, preventing defrost water from draining properly.
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The outside temperature sensor appeared to be faulty, sending bad data to the control module.
These three elements combined explained the abnormal behavior of the heat pump: it was no longer able to correctly complete its defrost cycles.
Repair: replacement of the probe and complete cleaning
Our technicians thoroughly cleaned the outdoor coil and base plate to remove all ice buildup. They then replaced the faulty temperature sensor with a genuine Mitsubishi part.
We then have:
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Checked the defrost heater and its power supply.
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Checked the R-410A refrigerant pressure to ensure no leaks were compromising performance.
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Cleaned and re-primed the condensate drainage to prevent future blockages.
Once the system was reset, the heat pump resumed normal operation. The customer immediately noticed a constant and stable return of heat to all rooms.
Result: restored efficiency and comfort regained
Thanks to this intervention, the heat pump has regained its full energy efficiency . We also recommended that the customer install an anti-frost protection under the unit to prevent melted snow from accumulating around the drain again.
At AirGreen, we always emphasize the importance of preventative maintenance. In this case, an annual inspection would have detected the sensor problem before it caused the system to completely freeze.
Why choose AirGreen for your HVAC repairs in Montreal
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Recognized expertise on all brands, including Mitsubishi, Fujitsu, Gree, Sharp, Midea and more.
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Fast and local service , covering Montreal, Laval, the North Shore and the South Shore.
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Accurate and transparent diagnosis before any repair.
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Original parts and full warranty on work carried out.
We understand the realities of our Quebec winters and know that an HVAC system must be ready to perform at all times. Whether it's a defrost failure , an abnormal noise , a refrigerant leak , or a complete compressor shutdown , our team is trained to intervene quickly and efficiently.
A typical intervention, a constant commitment
Every service call at AirGreen reflects our commitment to providing reliable, honest, and professional service . Our mission is simple: to ensure the lasting comfort of our customers while extending the life of their HVAC equipment .
This repair in LaSalle is a perfect example—a refurbished Mitsubishi wall-mounted heat pump, a satisfied customer, and a home ready to face the harsh Montreal winter.