An urgent service call in the middle of January
At AirGreen , we know that in winter, a heating breakdown can quickly become an emergency. This is exactly what a customer in Saint-Constant , on the South Shore of Montreal , experienced when he noticed that his Lennox electric furnace was no longer blowing hot air. Within hours, the indoor temperature had dropped by more than 5°C. Our team quickly arrived on site to restore comfort.
First inspection: an inactive fan
When we arrived, the Lennox furnace—a typical residential model connected to a central duct system—was showing signs of an internal electrical fault. The unit was receiving power, but there was no airflow through the heating vents. The blower motor remained silent, and the control board was showing a flashing red light.
Our technicians immediately began a complete inspection of the furnace's upper electrical compartment . This compartment housed the main control board , power relays , and internal fuses .
Detailed diagnosis of the fault
The diagnosis was carried out in several stages:
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Checking the supply voltage : 240 volts were reaching the furnace.
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Internal fuse inspection : no blown fuses.
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Blower motor check : motor resistance and continuity tested, motor was functional.
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Control Board Analysis : Reading Lennox fault codes indicating a faulty fan relay problem .
Upon disassembling the board, our technicians noticed evidence of overheating on the main relay, likely due to prolonged poor electrical contact . This anomaly prevented the blower motor from receiving the start signal.
Intervention: replacement of the Lennox control board
To fix the problem, our team:
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Removed the original control card ,
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Cleaned the power connectors and terminals,
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Installed a new original Lennox control board ,
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Checked the correspondence of the control wires (G, W, Y, R, C),
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Tested the operation of the blower motor in heating and ventilation mode.
After restarting, the furnace restarted perfectly : the motor started, the air flow was stable and the temperature at the outlets reached 42°C after a few minutes.
Technical analysis: causes and prevention of this type of breakdown
Control board failures are among the most common problems in electric and gas furnaces. In this case, the fault was caused by repeated micro-arcing in the relay, causing overheating and oxidation of the internal contacts.
Possible aggravating factors include:
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Excessive vibrations in the shaft or motor;
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Dust accumulation on electronic components;
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Winter condensation in the engine compartment;
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Poor ventilation of the technical room.
We therefore recommended annual preventive maintenance to the customer, including cleaning the blower compartment , checking the electrical connections and calibrating the thermal probes .
Regained comfort and a more reliable system
Once the board was replaced and testing was completed, the ambient temperature returned to normal. The customer immediately noticed an improvement in airflow , indicating that the engine was now operating at full capacity.
We also took advantage of the intervention to tighten the main electrical connections and measure the current intensity on each heating element - everything was in order.
At the end of the intervention, our technician provided the customer with a complete service report , including the electrical measurements taken and personalized advice to extend the life of their Lennox equipment.
Why Trust AirGreen for Electric Furnace Repair
At AirGreen, our expertise covers all residential and commercial HVAC systems, whether electric furnaces , central heat pumps , or hybrid systems .
Our clients in Montreal, Laval, Longueuil, on the North Shore and the South Shore benefit from:
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Certified technicians familiar with major brands (Lennox, Trane, Goodman, Bosch, etc.);
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Original parts guaranteed and installed according to CSA standards;
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Fast and precise diagnosis , thanks to advanced measuring tools;
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Transparent service , no hidden costs, with full explanation of the work.
AirGreen Tips for Maintaining Your Lennox Furnace
To avoid costly breakdowns and maximize your system's performance:
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Have the air filters cleaned every two to three months;
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Schedule a professional interview every fall;
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Keep the electrical compartment clean and dry ;
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Listen for unusual motor or relay noises —these often precede a failure.
A well-maintained furnace uses less energy and provides consistent comfort throughout the winter.
Conclusion: reliability by AirGreen
This Lennox electric furnace repair in Saint-Constant perfectly illustrates our approach: a methodical diagnosis , a rapid intervention , and a lasting result . The customer regained the comfort of his home in a few hours, while benefiting from a refurbished system that is better protected against future breakdowns.
At AirGreen , we pride ourselves on offering comprehensive, professional, and compassionate HVAC service—keeping every home in Greater Montreal comfortable, no matter the season.