A service call in the middle of winter
In the middle of a freezing January in Blainville , our AirGreen team received an emergency call for a TCL wall-mounted heat pump that was refusing to defrost properly. The customer, the owner of a single-family home painted a typical residential green, reported that his outdoor unit was making an abnormal noise and that the air blown inside was becoming lukewarm or even cold, despite a heating request.
With several centimeters of snow accumulating on the outdoor units, this was a critical situation: without rapid intervention, the system risked damaging its compressor and causing a complete shutdown.
Inspection and initial report
On site, we found that the TCL system had two stacked outdoor units —typical of a MultiZone installation, with each unit supplying different rooms in the home. The lower condenser was covered in a layer of compacted snow , while the upper one showed signs of excessive frost on the fan grille.
An initial electrical check confirmed that the automatic defrost mode was no longer activating correctly. The coil temperature sensor (thermistor) was giving an inconsistent reading, preventing the unit from detecting the need to defrost.
Detailed technical diagnosis
Step 1: Checking the sensors and probes
We first checked the electrical continuity of the temperature sensor connected to the electronic board. The resistance was outside the normal range (measured at 28 kΩ instead of the expected 15 kΩ at 0 °C), confirming a sensor failure.
Step 2: Test the Defrost Cycle
To isolate the problem, we manually forced defrost mode from the control board. The fan stopped as expected, but the compressor did not engage. Upon further inspection, we found that the defrost relay on the main board was showing signs of overheating and needed to be replaced.
Step 3: Repair and Recalibration
We replaced the temperature sensor and control board with genuine TCL parts, then recalibrated the operating parameters using our proprietary diagnostic interface. The defrost cycle was then successfully tested: the coils returned to their normal temperature, and the ice gradually evacuated.
Results after intervention
After a complete restart, the TCL MultiZone heat pump resumed smooth operation. Post-repair measurements indicated:
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Discharge temperature: 38°C after 10 minutes;
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Suction pressure: 118 psi , stable;
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No abnormal noise or vibration.
The customer found comfortable warmth throughout the house, even with an outdoor temperature of -18°C . We recommended manually clearing snow around the units after each storm to prevent airflow obstruction and extend the life of the system.
AirGreen Tips for Heat Pumps in Winter
The experience of this intervention in Blainville recalls some essential rules for optimizing the performance of HVAC systems in the Quebec climate :
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Always check the clearance around outdoor units (at least 30 cm on the sides and rear).
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Install a protective awning to limit snow accumulation and ice formation.
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Clean the coils twice a year, before and after the winter season.
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Schedule an annual AirGreen inspection : Our technicians can detect faulty sensors or boards before they cause a complete breakdown.
AirGreen expertise: long-term performance and reliability
Our interventions on the North Shore , in Montreal , Laval and on the South Shore demonstrate our commitment to providing precise, durable repairs that meet manufacturer standards . Each intervention is an opportunity for us to maximize the system's energy efficiency while minimizing costs for our customers.
Whether you use a TCL, Fujitsu, Gree, Sharp, Midea, or Bosch , our certified technicians handle R410A and R32 systems while respecting all environmental and safety standards. At AirGreen, we always prioritize repairs when feasible to avoid costly and unnecessary replacements.
A warmed house, strengthened confidence
Thanks to this intervention, the Blainville homeowner was able to get through the rest of the winter in renewed comfort. His TCL heat pump is now operating at peak efficiency, ready to face the rigors of the Quebec climate. Once again, AirGreen has demonstrated that with rigor and know-how, every HVAC problem has a sustainable solution .