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Réparation d’une thermopompe murale Lennox à Rosemont–La Petite-Patrie
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Repair of a Lennox wall-mounted heat pump in Rosemont–La Petite-Patrie

A quick service call in the middle of winter in Montreal

At AirGreen , our technicians are often called upon to intervene in demanding winter conditions. This time, our team went to the Rosemont–La Petite-Patrie neighborhood of Montreal to diagnose a Lennox wall-mounted heat pump whose outdoor unit was no longer starting.

The customer, a duplex owner, noticed that her system was no longer blowing hot air and that ice was beginning to form on the exterior ducts. This is a typical situation during freezing weather, especially when certain internal components are affected by humidity and extreme cold.

Diagnosis: an electronic card affected by humidity

Upon arrival, we noticed that the outdoor unit —an 18,000 BTU Lennox model —had an exposed control panel and showed signs of oxidation on the main circuit board.

Using our diagnostic tools, we checked:

  • The supply voltage of the compressor and the outdoor fan;

  • The integrity of the temperature sensors (external and evaporator);

  • The condition of the wiring connecting the indoor and outdoor units;

  • Refrigerant pressures , to ensure there were no leaks.

The verdict: the electronic card (PCB) was defective , causing the compressor and fan to fail to start.

Intervention: replacement and complete restoration

We replaced the electronic board with a compatible original Lennox module. To prevent the problem from recurring, we also:

  • Cleaned and dried the inside of the unit with a hot air jet;

  • Checked the waterproofness of the box and added moisture protection around the control box;

  • Revised the communication cable routing between units to prevent water infiltration;

  • Tested the system under power to ensure proper startup.

After these interventions, the heat pump resumed normal operation. The outdoor fan was running at full speed, the compressor was producing stable pressure, and the air blown inside reached 45°C after a few minutes.

Result: restored comfort and increased reliability

Thanks to this targeted and professional repair , the customer was able to regain the comfort of her home the same day. The Lennox system was optimized for Montreal's winter conditions , and we recommended:

  • To carry out preventive maintenance before each winter;

  • To keep snow clear around the outdoor unit;

  • Avoid prolonged exposure of the electronic card to the elements.

AirGreen Expertise: The Difference of a Certified Service

At AirGreen , we specialize in the repair, maintenance and installation of residential and commercial HVAC systems in Montreal, Laval, Longueuil, on the North Shore and the South Shore .
Our team is trained to work on all recognized brands: Lennox, Fujitsu, Midea, Gree, Mitsubishi, Trane, Bosch , and many others.

Each intervention is carried out according to the strictest standards in the HVAC sector, with a constant concern for reliability, safety and energy performance.

Technical details of the intervention

  • System Type: Lennox Wall-Mounted Heat Pump

  • Capacity: 18,000 BTU

  • Problem: Outdoor unit inactive, defective electronic board

  • Solution: PCB replacement, moisture protection, complete electrical check

  • Result: System restored, performance restored, comfort assured

Conclusion

This type of breakdown highlights the importance of regular HVAC system maintenance , especially in Quebec's harsh climates. Thanks to our experience, specialized tools, and stock of original parts, AirGreen ensures fast, durable, and safe interventions—even in the middle of winter.