Repair of a Fujitsu wall-mounted heat pump in Sainte-Dorothée

A service call in the middle of winter for a Fujitsu heat pump

At AirGreen , we recently received an urgent service call in Sainte-Dorothée (Laval) for a Fujitsu wall-mounted heat pump that refused to heat even though the outside temperatures had plunged below -15°C. The unit, installed on a north-facing wall, was covered in snow and frost , and the customer noticed that the outdoor unit was no longer automatically defrosting .

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Diagnosis: A system suffering from excessive icing

Upon arrival, we found that the Fujitsu outdoor condenser was mechanically sound, but blocked by a thick layer of ice under the fan. This phenomenon, common in winter, can be aggravated by a malfunction of the defrost sensor or the reversing valve relay .

Steps of our diagnosis:

1. Automatic defrost mode check : the system no longer switched correctly to “heat pump defrost” mode.

2. Coil temperature sensor test : erroneous reading - thermistor read -5°C when actual surface reached -18°C.

3. Reversing valve relay inspection : slight internal moisture deposit.

4. Refrigeration cycle check : slightly low pressure, suggesting ice buildup restricting flow.

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Repair and recommissioning

We replaced the defrost sensor (thermistor coil sensor) and cleaned the reversing valve relay . Then we carried out a complete manual defrost using a jet of hot air calibrated to avoid damaging the exchanger fins.

Once the system was restarted, the compressor returned to its normal cycle, and the discharge temperature quickly reached 46°C in heating mode , proof that the heat pump was once again operating at full efficiency.

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Results: comfort restored and performance restored

The customer immediately felt a marked difference—the indoor temperature rose from 18°C ​​to 22°C in less than an hour. In addition, the heat pump, now cleared and recalibrated, resumed its automatic defrost cycle without any issues.

Recommended points for improvement:

• Installation of a protective roof above the condenser , to limit snow accumulation.

• Preventive cleaning of the probe during each winter maintenance .

• Annual inspection of exposed refrigerant wiring and insulation .

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What this intervention demonstrates

This service call perfectly illustrates the robustness of Fujitsu systems and the importance of preventative winter maintenance . Even the best heat pumps can malfunction during extreme weather conditions.

Our AirGreen technicians are specifically trained on Fujitsu systems , allowing us to quickly identify and correct electronic or thermal faults, while adhering to manufacturer protocols.

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Why choose AirGreen in Laval and on the North Shore

• Fast service even in periods of intense cold .

• Fujitsu certified technicians qualified in inverter heat pumps.

• Accurate diagnosis with professional instruments (digital pressure gauges, calibrated thermocouples).

• Service covering all of Greater Montreal: Laval, Montreal, Longueuil, North Shore and South Shore.

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A heat pump ready for the Quebec winter

Following this repair, the customer's Fujitsu heat pump operates smoothly, even below -20°C. Thermal comfort has returned, energy consumption has stabilized, and the outdoor installation remains protected against future snow accumulation.

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At AirGreen , we believe that the performance of a heat pump depends as much on the quality of maintenance as on the expertise of after-sales service .
That's why we offer complete four-season maintenance , so that every customer can enjoy lasting, energy-efficient comfort , regardless of the whims of the Quebec climate.

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Need professional service for your Fujitsu heat pump?
Contact AirGreen Climatisation & Chauffage today — your trusted HVAC partner in Montreal, Laval, Longueuil, the North Shore, and the South Shore.