A Typical Winter Service Call: When Snow Puts Your Comfort to the Test
At AirGreen , we often receive calls in the middle of winter for wall-mounted heat pumps that stop working properly due to ice or snow buildup. This is exactly what happened to a residential customer in the Sainte-Dorothée sector of Laval , owner of a Mitsubishi Electric Mr. Slim R410A , a unit known for its performance, but sensitive to extreme weather conditions if not properly maintained.
The context of the intervention
One January morning, our client contacted us after noticing that his outdoor heat pump was no longer blowing warm air and that frost was building up on top of the unit . Located near a fence and exposed to the wind, the outdoor unit was covered in a thick layer of frozen snow. As a result, the system was entering frequent defrost mode , consuming a lot of energy without actually heating the house.
On-site diagnosis: a classic defrosting problem
Upon our arrival, we carried out a complete inspection of the Mitsubishi Mr. Slim R410A , a wall-mounted heat pump model very popular in Laval residences. Here are our technician's findings:
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Ice buildup on the fan and condenser fins.
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Partial blockage of the air intake due to the proximity of the fence.
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Frosted outdoor temperature sensor , causing incorrect reading and ineffective defrosting.
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Drainage blocked by melted snow , preventing proper water drainage during the defrost cycle.
These problems, although common, can reduce the energy efficiency of a wall-mounted heat pump by up to 40% and accelerate compressor wear.
Intervention and restart
Our certified technician proceeded step by step:
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Safely remove snow from the unit and completely defrost with warm water (never with steam or a hammer, to avoid damaging the fins).
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Checking the temperature probe and preventive replacement, the part having been weakened by repeated freeze-thaw cycles.
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Cleaning the fan and condenser using a biodegradable product designed for HVAC systems.
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Cleared the condensation drain and installed a small baffle to direct melted snow away from the base of the unit.
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Complete operating test in heating and defrosting mode: the cycle stabilized, the R410A gas pressure was compliant, and the thermal efficiency returned to its optimal level.
Result: comfort restored and efficiency restored
After this intervention, the Mitsubishi Mr. Slim heat pump resumed normal operation. The customer noticed an immediate difference in indoor comfort and a reduction in compressor noise . The unit no longer defrosted too frequently, a sign that heat exchange had become efficient again.
We also advised the client on some good winter practices:
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Maintain at least 30 cm of clearance around and above the unit.
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Install snow protection (roof or partial shelter) without obstructing ventilation.
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Check regularly that the fan is spinning freely and that the drain is not frozen.
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Schedule preventative HVAC maintenance in the spring to clean the coils and check the refrigerant charge.
Why these interventions are essential
Even the best wall-mounted heat pumps, like the Mitsubishi Mr. Slim R410A , require regular maintenance to withstand Quebec winters. Humidity, snow, and freezing cycles can cause:
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Premature compressor failures .
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Abnormal electricity consumption .
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Refrigerant leaks if frost causes micro-cracks in the lines.
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Mechanical noises due to fan imbalance.
At AirGreen, we often see units that are well-installed but poorly protected against snow . A simple adjustment, such as raising the wall bracket or adding a deflector, can extend the life of the system by several years.
AirGreen expertise in Sainte-Dorothée and throughout the North Shore
Our team of Mitsubishi wall-mounted heat pump repair experts operates throughout Laval, Montreal, Longueuil, the North Shore, and the South Shore . Every service call is handled with care: we diagnose, repair, optimize, and advise to ensure lasting comfort and maximum energy efficiency.
Whether it's for ineffective defrosting, an electrical failure, an abnormal noise or simple maintenance, our Mitsubishi certified technicians are trained to intervene quickly and efficiently , even in very cold weather.
In summary
The intervention in Sainte-Dorothée perfectly illustrates the importance of regular preventative maintenance . A well-maintained Mitsubishi wall-mounted heat pump, even after several winters, remains a durable, efficient and energy-efficient investment.
At AirGreen , we don't just repair: we ensure every customer has peace of mind and long-term performance of their HVAC system.