A central system down in the middle of summer
At AirGreen , we know that a central air conditioning system that stops working in the middle of a hot day can quickly turn a home's comfort into total discomfort. That's exactly what happened to a family in Brossard , on Montreal's South Shore , when their Lennox central heat pump stopped blowing cool air.
Symptoms observed: warm air and silent compressor
The customer contacted us after noticing that the system was blowing lukewarm air , even though the thermostat was set to 21°C. Upon arriving on site, our technicians immediately noticed that:
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The compressor would not start , although the outdoor unit fan was running.
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The inrush current at startup seemed abnormally low.
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The refrigerant pressure remained stable, indicating that there was no leak.
These signs pointed to a failure of the start relay or the compressor capacitor , two components frequently put under strain during periods of intense heat.
Complete diagnosis: electrical tests and verification of the refrigeration circuit
Our experts carried out a thorough electrical inspection :
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Measurement of the supply voltage at the compressor input.
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Continuity check on the main contactor .
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Capacitance test on the starting capacitor .
The results confirmed a weakened capacitor —its actual capacity was down to 60% of its nominal value. This defect prevented the compressor from starting properly, causing complete cooling failure.
Repair: capacitor replacement and return to service
We replaced the faulty capacitor with a certified Lennox part and then performed a restart test. Upon first start-up:
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The compressor started normally .
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The refrigeration pressures have balanced within the ideal ranges.
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The air distributed inside quickly dropped to 12°C at the outlet of the ducts .
Once the system was stabilized, we cleaned the outdoor condenser , removed any plant debris that had accumulated around the unit, and checked the amperage draws to confirm everything was operating at full efficiency.
Preventive maintenance: advice from our technicians
Our technicians took advantage of this visit to remind the customer of some good maintenance practices:
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Have the condenser coils cleaned every spring.
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Replace air filters every 2 to 3 months.
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Check clearance around the unit to avoid obstruction of ventilation.
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Schedule a complete annual inspection before each summer.
These simple actions extend the life of the heat pump and ensure optimal energy efficiency.
Result: comfort restored and system optimized
After our intervention, the Lennox central heat pump in the Brossard residence regained its full performance. Cooling became rapid and uniform again , and the client noticed an immediate drop in compressor noise .
This repair demonstrates how a minor component like a capacitor can immobilize an entire system, but also how a quick and methodical intervention can restore comfort to a home in less than an hour.
AirGreen expertise: sustainable and professional solutions
At AirGreen , every repair is carried out with rigor, transparency, and attention to detail. Our technicians are certified to work on all major brands, including Lennox, Trane, Goodman, Carrier, Bosch, Fujitsu, and Midea .
We operate daily in Montreal, Laval, Longueuil, and across the North Shore and South Shore , offering:
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Accurate diagnostics using electronic measuring instruments.
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Original or equivalent quality parts .
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Fast and courteous service , adapted to each type of residence.
AirGreen: the trusted HVAC partner in Brossard
Whether it's preventative maintenance , an urgent repair or a complete central system replacement , our mission remains the same: to ensure the comfort, performance and durability of your HVAC system.
AirGreen is the promise of clean air, a stable indoor climate and service that meets your expectations — everywhere in Brossard and the greater metropolitan area.