Fast diagnosis and efficient repair of a frozen HVAC system in the middle of winter
At AirGreen , we often respond when freezing temperatures put HVAC systems under strain. This service call in Sainte-Thérèse , on Montreal's North Shore , perfectly illustrates the speed and thoroughness of our team in the face of a winter emergency.
Context of the intervention
Our client contacted us one February morning after noticing that her Extreme central heat pump was no longer heating properly. The outdoor unit, installed against the brick wall of her home, seemed frozen solid, while the air blown inside the house was lukewarm despite the thermostat being set at 22°C.
A quick on-site inspection revealed a common but potentially damaging problem: the outdoor unit was completely clogged with snow and partially frosted over , preventing the heat pump from properly completing its defrost cycles.
Step 1: Complete Inspection and Diagnosis
Upon our arrival, we carried out a complete check of the system:
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Visual inspection of the Extreme condenser: ice accumulation around the fins.
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Airflow check : Partial obstruction caused by a snow barrier near the rear grille.
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Defrost cycle check : no switch to defrost mode, which indicated a sensor or control board problem .
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Compressor analysis : starting current remained within standards, eliminating a motor problem.
Step 2: Snow removal and testing of electronic components
After carefully freeing the unit and freeing the fan, we isolated the root cause of the problem:
The defrost temperature sensor was sending an incorrect reading to the electronic board. This sensor, slightly displaced from its original position due to vibration, was no longer detecting the actual temperature of the exchanger.
We have :
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Recalibrated the defrost sensor .
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Cleaned the electrical connectors and checked for continuity.
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Restarted the system to observe the complete defrost sequence.
A few minutes later, the frost began to melt evenly on the exchanger: proof that operation had been restored.
Step 3: Performance Optimization and Prevention
To avoid any recurrence, we advised the client:
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To install a wooden side protection barrier to reduce direct exposure to the wind (already started in the photo).
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Maintain a minimum clearance of 60 cm around the unit for good airflow.
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Schedule preventive maintenance before each winter to check the sensors and automatic defrosting.
We also measured the indoor air outlet temperature after repair: 35°C in heating mode , confirming that the heat pump was returning to full capacity.
Result: comfort restored and efficiency restored
Thanks to this intervention, the client regained the thermal comfort of her home and avoided premature replacement of expensive components.
The Extreme central heat pump now operates at optimal efficiency despite the demanding winter conditions typical of the North Shore .
Why choose AirGreen for your HVAC emergencies?
Our certified technicians have extensive expertise on Extreme, Lennox, Midea, Fujitsu, Gree systems and more .
Every diagnosis is carried out with precision, and our repairs are guaranteed.
We cover all of Greater Montreal— Montreal, Laval, Longueuil, the North Shore and the South Shore —with fast, efficient and lasting interventions.
To remember
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Problem : Faulty defrost sensor causing excessive icing.
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Solution : Repositioning and recalibrating the sensor + cleaning the condenser.
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Result : Heating restored, unit optimized, consumption reduced.
At AirGreen , we believe that a well-done repair extends the life of your system and ensures reliable comfort, even below -25°C.