A broken heat pump on a flat roof: a challenge well mastered by our AirGreen team
At AirGreen , we carry out HVAC repairs every day throughout Greater Montreal. Recently, our team traveled to Sainte-Dorothée (Laval) to diagnose and restart a Sharp wall-mounted heat pump installed on a residential flat roof . This is a typical situation in multi-unit buildings, where managing outdoor installations must balance efficiency, safety, and sustainability.
Background to the call
The customer contacted us after noticing that their heat pump was no longer producing heat. The outdoor unit, a Sharp model mounted on a metal bracket , appeared to be inactive despite having power. In addition, the unit was displaying a flashing error code on the indoor unit. Before our arrival, the customer had already tried resetting the circuit breaker , without success.
Our mission: to identify the cause of the breakdown, assess the condition of the compressor and check the integrity of the electrical and refrigeration installation.
On-site diagnosis: rigorous method and safety above all
Once on the roof, our certified technician immediately checked:
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Power supply via wall disconnect box;
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The pressure switches and control board inside the outdoor module;
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Refrigeration connections , looking for leaks or pressure imbalance.
A visual inspection revealed that the control wiring between the heat pump and the wall box showed signs of oxidation—likely caused by exposure to the elements. The rest of the system, including the insulated refrigerant lines, appeared intact.
A multimeter measurement confirmed unstable voltage at the main relay, which pointed our diagnosis towards a faulty control board .
Intervention: replacement of the electronic card and return to service
After confirming with the customer, we proceeded to completely replace the main electronic board of the Sharp compressor. This part is crucial: it manages communication between the indoor and outdoor units, as well as power modulation.
Key steps of the intervention:
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Complete power cut;
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Safe disassembly of the control panel;
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Removing the defective card and installing an original Sharp card;
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Checking communication wiring and grounding circuit ;
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Power up and complete test of heating and air conditioning modes .
We then measured the R410A refrigerant pressures to ensure the system was operating within the manufacturer's recommended parameters.
Result: restored performance and satisfied customer
As soon as the intervention was completed, the heat pump resumed normal operation. The Sharp compressor started without error, and the indoor unit delivered stable and rapid heat. After 20 minutes of continuous testing, thermal efficiency was optimal, with a temperature differential of 12°C between the intake and exhaust air—an excellent indicator of efficiency.
We also advised the client:
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To visually inspect electrical connections at least once per season;
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Avoid any accumulation of snow or debris around the outdoor unit;
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And to plan annual preventive maintenance , essential to extend the life of the system.
Technical analysis and AirGreen best practices
This type of intervention perfectly illustrates the importance of:
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Correct installation of the units on a stable support;
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Electrically waterproofed for flat roofs exposed to the elements;
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And preventive maintenance of electronic components.
Our AirGreen certified technicians follow strict procedures during every service call, ensuring the safety, performance and compliance of residential HVAC systems in Montreal, Laval and the North Shore.
Local expertise serving sustainable comfort
Sharp heat pump repair is one of our specialties, but our expertise extends to all major brands – Midea, Fujitsu, Gree, Lennox, Goodman, Trane, Zephyr , and many more.
No matter the make or model, our team is equipped to quickly diagnose the most complex problems, whether electrical, mechanical or refrigeration .
Thanks to our local presence in Laval and Montreal, we guarantee:
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Fast response times ;
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Genuine parts and installation compliant with CSA standards;
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And courteous, transparent and professional service at every visit.
Conclusion: a successful repair, renewed confidence
This service call in Sainte-Dorothée demonstrates our commitment to providing reliable and durable solutions for every HVAC system.
The Sharp heat pump , now fully operational, will provide optimal comfort all year round, summer and winter.
At AirGreen , we believe that good service is more than just a repair: it's peace of mind restored to our customers, and a perfectly balanced indoor climate.