A call for service at height: rooftop unit in Ville Mont-Royal
At AirGreen , our interventions often take place in a variety of settings: residential ground floors, condo buildings, or rooftop terraces. On this day, our team traveled to Ville Mont-Royal , where a client reported a complete shutdown of their Gree wall-mounted heat pump installed on the flat roof of their building.
The unit, a Gree Multi+ wall-mounted model , served two separate indoor areas. The customer had noticed for a few days that one of the indoor units was blowing lukewarm air , while the other was no longer starting at all.
Complete roof diagnosis
Our team undertook a thorough, step-by-step diagnosis to determine the cause of the failure.
Step 1: Checking the power and electronic cards
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Stable 240V power supply confirmed.
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Fuses intact, no short circuits detected.
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However, the outdoor unit control module was not sending any signals to the electronic expansion valves.
Step 2: Inspect Wiring and Connections
In rooftop installations, electrical connections are often exposed to moisture and temperature fluctuations. Upon opening the side box, we discovered traces of oxidation on the main control board , probably caused by condensation.
Step 3: Checking the refrigeration circuit
The R-410A gas pressures were normal, ruling out a leak. The compressor, meanwhile, showed abnormal resistance on the start winding , indicating a faulty power board .
Repair: Replacement of the external control board
After discussion with the customer, we proceeded to completely replace the main electronic card .
The steps taken:
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Safe disconnection of the unit.
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Removal of the oxidized card and complete cleaning of the compartment.
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Installation of a new Gree OEM card , updated version compatible with the model's firmware.
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Communication test with indoor units.
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Complete restart of the system with measurement of electrical intensities and blowing temperatures.
The result: stable operation, smooth compressor start-up and an air outlet temperature of 10°C.
Results and recommendations
The customer immediately noticed the return of comfort and the disappearance of the error noise at startup.
We then added additional moisture protection with a dielectric sealant and an insulating membrane on the lead-in cables —an essential precaution for all flat roof installations exposed to the elements.
At AirGreen , we always insist on prevention :
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Perform annual preventive maintenance , particularly for exterior roof installations.
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Check the ventilation of the units and clear any dust accumulated on the fins.
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Inspect electrical boxes in the spring, before the air conditioning season.
AirGreen expertise at the service of reliability
This intervention in Ville Mont-Royal illustrates our commitment to combining technical rigor and durability . Thanks to our experience with brands like Gree, Fujitsu, Midea, Sharp and Zephyr , we know that the reliability of an HVAC system depends as much on the quality of the components as on regular maintenance and protections applied on site.
Our teams respond quickly throughout Greater Montreal, Laval, Longueuil, the North Shore and the South Shore , for repairs to wall-mounted heat pumps, MultiZone, and central systems — always with attention to detail and lasting performance.
AirGreen — reliable and long-lasting HVAC repairs, even on Montreal's most demanding roofs.