An urgent service call for a unit that would not start
At AirGreen , we were recently called to Terrebonne , on the North Shore of Montreal , for a complete breakdown of a Lennox central heat pump . The client, the owner of a single-family brick home, had noticed that his system was no longer blowing cool air despite the thermostat being set at 22°C.
With outside temperatures exceeding 30°C, this was an emergency that our team dealt with the same day.
First observation: a silent external compressor
Upon arriving on site, our technician quickly noticed that the Lennox outdoor unit , installed on a sturdy wall bracket, was no longer starting . No fan noise, no compressor start – a typical sign of a power supply failure or compressor start .
We immediately began a complete check of the electrical circuit and the main contactor .
Step 1: Complete electrical diagnosis
Our tests revealed:
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Correct input voltage (240V), confirming that the house power supply was working.
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A lack of voltage at the contactor output , indicating a control problem.
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Upon inspection, we discovered an oxidized contactor relay —a common occurrence caused by moisture and the age of the device.
The relay therefore prevented the electrical circuit from closing and blocked the compressor from starting.
Step 2: Internal inspection of the condenser
To ensure no other components were damaged, we also checked:
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The compressor start capacitor .
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The condition of the power cables and connection terminals .
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The pressure of the refrigerant , in order to exclude any leaks or drop in charge.
The measurements were in accordance with the specifications of the manufacturer Lennox. The main problem remained mechanical and electrical at the level of the contactor .
Step 3: Contactor Replacement and Startup Test
We immediately replaced the 2-pole 30A contactor , a genuine Lennox part, and then tightened all electrical connections to prevent any risk of future overheating.
After power was restored, the compressor and fan restarted instantly , demonstrating that the control circuit was operational again.
The system then resumed its normal cooling cycles, with air leaving the ducts at 11°C —proof of optimal performance.
Step 4: Preventive maintenance and cleaning of the condenser
Taking advantage of the intervention, our technician carried out a complete cleaning of the grille and fins of the condenser . In fact, the outdoor unit, exposed to the elements, had an accumulation of dust and pollen, which reduces heat dissipation.
The interview included:
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Gentle suction of the fins to avoid bending them.
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Application of a biodegradable cleaner to restore airflow.
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Low pressure flush and inspection of the base of the unit to ensure proper condensate drainage.
These steps have reduced energy consumption and ensured faster cooling of interior parts.
Results after intervention
After repair and maintenance:
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The indoor temperature dropped from 27°C to 22°C in less than 30 minutes.
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Power consumption has decreased thanks to the good efficiency of the compressor.
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The customer found stable and silent thermal comfort .
We have also scheduled an automatic annual maintenance reminder , ensuring that the Lennox system remains efficient year after year.
AirGreen Recommendations for Central Heat Pump Owners
At AirGreen, we remind you that central HVAC systems , like this Lennox heat pump in Terrebonne , must be inspected at least once a year .
Here are our maintenance tips:
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Clean the air filters every 2 to 3 months.
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Clear the area around the outdoor unit (at least 60 cm free around it).
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Watch for unusual noises or erratic starts.
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Call a certified technician at the first sign of electrical failure.
Prompt intervention prevents costly breakdowns and extends compressor life.
Why choose AirGreen for your Lennox repairs?
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Lennox technicians specialized and trained on central HVAC systems.
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Genuine parts for long-lasting, compliant repairs.
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Fast and professional service throughout Greater Montreal.
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Complete transparency on diagnosis and costs.
Our goal: to restore your comfort without compromise, with service that is fast, precise and courteous .
Conclusion: A refurbished Lennox heat pump in Terrebonne
Thanks to a rigorous diagnosis and targeted repair , the Lennox central heat pump in this Terrebonne residence is now operating at full capacity.
The intervention demonstrates the importance of preventive maintenance and professional monitoring for residential HVAC systems.
At AirGreen , we are proud to serve homes in Montreal, Laval, Longueuil, the North Shore and the South Shore , guaranteeing the performance and reliability of every system we maintain.