Air conditioning failure on balcony in the heat
When a client in Saint-Lambert , on Montreal's South Shore , contacted us during a heat wave, their Lennox HVAC system was no longer cooling their apartment. Installed on a narrow balcony , the Lennox wall-mounted heat pump was showing clear signs of fouling and fatigue. At AirGreen , we know that the location of an outdoor unit directly influences its performance—and this case was a perfect example.
The context of the call
The customer explained that his Lennox heat pump was working, but the air coming out inside remained lukewarm , even after several minutes. The unit seemed to be struggling, and a faint metallic humming sound was coming from the outdoor condenser installed on the balcony. In addition, the electricity consumption had increased unusually.
Our mission: to quickly diagnose the problem, despite restricted access and a unit exposed to direct sunlight.
Diagnosis: Lack of maintenance and a clogged condenser
After a complete inspection, our technician identified several anomalies:
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Condenser fins clogged with dust and pollen.
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Reduced heat exchange , causing a rise in pressure in the compressor.
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Fan dirty and slightly unbalanced.
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Aging run capacitor , measured at 60% of its nominal capacity.
These combined factors explained why the Lennox heat pump was running continuously without reaching the desired temperature.
Steps of repair
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Power cut and secure the workstation on the balcony.
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Complete cleaning of the outdoor condenser using a biodegradable product designed for HVAC units.
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Blow with compressed air to clear the fins and restore airflow.
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Checking the fan and replacing its slightly loose fixing shaft.
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Replaced the run capacitor with an original Lennox model, calibrated for this 12,000 BTU series.
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Load operating test , followed by pressure and temperature measurement.
After 15 minutes of testing, the discharge pressure stabilized, and the indoor air began to blow at 8°C —proof that heat exchange had returned to optimal levels.
Result: restored performance and extended lifespan
Thanks to this intervention, the Lennox heat pump has regained its full capacity.
The customer immediately noticed a reduction in noise , better energy efficiency , and above all, rapid cooling of his home.
We recommended installing a protective sunshade to reduce overheating of the south-facing outdoor unit.
Prevention: Maintain to avoid overheating
This type of balcony installation is very common in Montreal, Laval and the South Shore .
However, care must be taken to:
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Leave at least 30 cm of free space around the unit for good ventilation.
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Clean the condenser twice a year , especially after the pollen season.
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Avoid the accumulation of water or dust on the balcony floor.
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Check the unit's mounting and stability , especially in winter.
💡 AirGreen Tip : A simple annual cleaning can extend the life of a compressor by more than 5 years and prevent costly breakdowns due to overheating.
AirGreen expertise: precision above all
Each intervention we carry out is based on a methodical diagnosis and total transparency .
Our technicians, specialized in HVAC repair and maintenance , work on all recognized brands:
Lennox, Fujitsu, Midea, Gree, Sharp, Trane, Goodman, Zephyr, Bosch , and many more.
Whether for preventative maintenance , urgent repairs , or a complete installation , we offer solutions adapted to each type of housing — from urban condos to residential duplexes.
In conclusion
This intervention in Saint-Lambert perfectly illustrates the AirGreen philosophy: repairing intelligently, sustainably and efficiently .
By replacing a weakened capacitor and cleaning the external condenser, we restored system performance without major replacement.
Fast, accurate and professional service – exactly what our customers on the South Shore are looking for.
AirGreen Air Conditioning & Heating
Experts in repair, maintenance and installation of HVAC systems in Montreal, Laval, Longueuil, on the North Shore and the South Shore.