A crucial service call in the middle of the hot season
At AirGreen , we were recently contacted for a service call in Brossard , on the South Shore of Montreal , for a Lennox central heat pump installed on an exterior wall bracket. The owner had been noticing abnormal operation for several days: the machine would start, but the compressor would stop prematurely, leaving the house to heat up in the middle of a heatwave.
A typical but demanding installation
The heat pump, a high-efficiency Lennox model , was mounted directly onto a metal wall bracket securely anchored to the brick facade of the residence. This type of installation, ideal for avoiding contact with the ground and limiting vibrations, requires special attention to air circulation and system stability .
Upon our arrival, our technician performed a complete assessment of the HVAC system , starting with:
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Checking the electrical connections and the external circuit breaker .
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Analysis of internal error codes recorded by the Lennox control board.
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Pressure measurement of the refrigerant circuit to identify any possible imbalance.
Diagnosis: Overheating due to a faulty fan
Initial measurements revealed an abnormally high condensation pressure , indicating a condenser cooling problem. After removing the top cover, the cause was confirmed:
The main fan motor was showing signs of failure—it was running at reduced speed, causing the compressor to overheat and cyclical safety shutdowns.
This type of failure is typical on central units exposed to direct sunlight: the fan motor , under continuous stress, ends up losing torque due to heat and wear of the starting capacitor.
Intervention: capacitor replacement and motor overhaul
Our technicians carried out a two-stage intervention:
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Replaced the starting capacitor with an original Lennox model, calibrated to the motor specifications.
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Thorough cleaning of the condenser using a biodegradable cleaner to remove dust accumulated on the fins.
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Lubrication and mechanical inspection of the fan motor , to ensure smooth and quiet operation.
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Load restart test , with monitoring of evaporation pressures and temperatures.
Once the repair was completed, the pressures returned to normal, and the machine was able to reach a stable operating cycle. The customer immediately felt a noticeable difference in the interior temperature , with restored comfort and quiet operation.
Prevention and recommendations
Before leaving the premises, our technician took the time to advise the owner on some good practices to extend the life of his heat pump:
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Clean the exterior grills at the beginning and end of each season.
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Check that branches and plants do not obstruct air circulation around the condenser.
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Schedule a complete HVAC maintenance once a year to prevent overheating and detect any mechanical weaknesses before the summer season.
An example of AirGreen expertise on the South Shore
This intervention once again demonstrates the rigor and versatility of the AirGreen team , capable of quickly intervening on all types of central heat pumps — whether Lennox, Trane, Goodman, Carrier or Mitsubishi models.
Our goal: to restore interior comfort while optimizing the energy efficiency of each system.
Thanks to our active presence in Montreal, Laval, Longueuil and on the South Shore , we provide fast, reliable and long-lasting service for all your residential and commercial HVAC repair needs.