A diagnosis on the roof of a West Shore residence
During the hot season, a Goodman central heat pump installed on the roof of a residence in Beaconsfield , in the West Island of Montreal, stopped producing cold air. The owner immediately contacted AirGreen , aware of the importance of an efficient HVAC system to ensure indoor comfort during heat waves. Our team quickly arrived to perform a complete diagnosis and restore this essential unit to service.
A rooftop unit exposed to the elements
The Goodman condenser, mounted on a metal stand, was exposed to direct sunlight and harsh weather. These conditions often accelerate the wear of critical components such as:
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the condenser fan ,
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the starting capacitor ,
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and moisture-sensitive electrical contacts .
Upon arrival, we noticed that the fan was no longer spinning despite the indoor thermostat being actively controlled. The unit was emitting a low humming noise , typical of a weakened capacitor unable to start the fan motor.
Steps of the diagnosis carried out by AirGreen
Our technician followed a methodical procedure to isolate the exact cause of the failure:
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Turn off the main circuit breaker to secure the intervention area.
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Opening the condenser side panel to access the electrical components.
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Visual inspection : no signs of burning or damaged cable.
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Measuring the capacitor using a capacitance multimeter. Result: 9.4 µF for a nominal 15 µF capacitor — well below tolerance.
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Relays and main contactor checked — tested and working.
So the diagnosis was clear: the fan start capacitor needed to be replaced.
Repair and restart
We installed a new Goodman compatible capacitor of the same capacity and high temperature rating, designed to withstand direct sunlight on roofs. After reassembly, our technician restored power and observed an instant restart of the fan .
The refrigeration circuit pressures were then checked:
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Suction pressure: 120 psi
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Discharge pressure: 340 psi
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Superheating and subcooling within manufacturer's tolerances.
No signs of refrigerant leakage were detected — compressor performance remained excellent.
Additional check of the internal system
As always at AirGreen , we don't just fix the symptom. We checked the communication between the outdoor unit and the indoor electric furnace , to confirm that the control relay (24V) was sending the start signal. An inspection of the air filtration was also performed: the MERV 11 pleated filter was clean and properly installed.
This preventative step is essential, as restricted airflow inside can cause the compressor to overheat and damage the new condenser in the medium term.
Result: comfort restored and reliability assured
In less than an hour and a half, the Goodman central heat pump was back operating at full capacity. The owner immediately noticed the return of consistently fresh air to every room. We concluded our intervention with personalized recommendations:
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Install a protective sunshade to extend the life of the electrical components on the roof.
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Schedule annual preventative maintenance including coil cleaning and capacitor checking.
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Monitor fan vibration , a potential indicator of motor imbalance.
The Importance of Capacitor in HVAC Systems
The start capacitor acts as a power reserve to initiate the movement of the fan or compressor motor. Over time, its capacity decreases due to:
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extreme temperature variations ,
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frequent start cycles ,
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or even moisture accumulation in the electrical box.
A weakened capacitor results in:
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a fan that no longer starts,
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a noisy compressor,
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increased electricity consumption,
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and, ultimately, a complete system failure.
AirGreen: your HVAC partner in Montreal and on the West Shore
Whether for urgent repairs or preventative maintenance , our team works on all types of central heat pumps in Montreal, Laval, Longueuil, the North Shore and the South Shore . We work with the most recognized brands such as Goodman, Lennox, Trane, Bosch and Midea , and we always favor original parts to guarantee reliability and performance.
Each service is accompanied by a detailed intervention report and personalized advice to help our customers maximize the lifespan of their equipment.
Conclusion: fast, accurate and professional service
Thanks to rapid intervention and a thorough diagnosis, the Beaconsfield family was able to return to the comfort of their home the same day. At AirGreen , our commitment is clear: to offer lasting repairs, transparent explanations, and local expertise recognized throughout Greater Montreal.