An HVAC system shut down in the middle of winter
At AirGreen , we recently received a service call in Saint-Constant , on the South Shore of Montreal , for a KoolKing wall-mounted heat pump that was no longer starting despite freezing temperatures. The customer, aware of the importance of heat pump heating in winter, had noticed that his outdoor unit was no longer defrosting and that a slight mechanical noise was coming from the compressor.
Our mission: to diagnose the exact cause of the breakdown and put the system back into service quickly , while ensuring its long-term performance.
Initial diagnosis: an overloaded compressor and a fan blocked by ice
Upon arrival, we found that the outdoor unit—a compact KoolKing condenser installed under a metal staircase —was surrounded by snow and ice, restricting airflow around the fan. This type of installation, while useful for protecting the equipment from direct weather, can sometimes interfere with the heat pump's natural defrosting .
Our technicians first carried out:
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A complete electrical check of the compressor and start relay;
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An inspection of the defrost cycle and control board;
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A mechanical assessment of the fan , blocked by an accumulation of ice on the blades.
The verdict: the system had gone into thermal protection due to excess frost, preventing the compressor from running properly.
Intervention: manual defrosting and calibration of the outside temperature sensor
We performed a controlled manual defrost of the unit, using low-pressure warm air to avoid damage to the evaporator fins. Next, the outdoor temperature sensor was recalibrated: it was slightly out of adjustment, causing the automatic defrost mode to trigger late.
Our technicians also cleaned the fan guard and replaced the unit on its anti-vibration mounts, which were slightly misaligned. This realignment promotes better drainage of defrost water and prevents ice from forming under the unit.
Final tests: stable and quiet performance
After restarting, we measured the R-410A refrigerant pressures , confirming normal operation. The defrost cycle then activated automatically after 30 minutes of operation, proving that the electronic control system had regained responsiveness.
The customer immediately noticed a stable flow of warm air inside and reduced operating noise outside. Thanks to careful calibration, the KoolKing heat pump regained its original efficiency, even at -15°C.
Prevention: our tips for avoiding winter breakdowns
To extend the life of a wall-mounted heat pump , we recommend to all our customers:
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To clear snow and ice around the compressor after each storm;
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Avoid installing the outdoor unit in a confined space (such as under a closed staircase);
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Perform a complete annual maintenance before winter to check the sensors and defrosting;
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Use a raised support to promote the flow of condensate.
These simple measures can prevent 80% of winter service calls related to heat pumps.
AirGreen: your HVAC partner in Saint-Constant and throughout Greater Montreal
At AirGreen , every repair is carried out with rigor and attention to detail. We work on all brands of wall-mounted heat pumps , including KoolKing, Fujitsu, Gree, Sharp, Midea, Zephyr and Bosch , and serve the entire Greater Montreal area, from Laval to the North Shore , including Longueuil and the South Shore .
Our team is trained to diagnose quickly , repair efficiently and prevent future problems . Each client benefits from personalized service, adapted to the configuration of their home and the Quebec climate.
Result: comfort restored and peace of mind assured
A few hours after our departure, the customer confirmed that his KoolKing heat pump was working perfectly , maintaining constant heat despite the cold outside. This type of repair illustrates our commitment: ensuring the comfort of Quebec homes, even in the most demanding conditions .
At AirGreen, your comfort doesn't wait —and every service call is a promise kept.