Real cases from Montréal, Laval, and the South Shore that go beyond online guides and require on-site expertise from AirGreen
In the world of residential HVAC in Québec, wall-mounted heat pumps have become essential. They’re efficient, discreet, cost-effective — and yet, some problems that arise after installation seem to defy logic. Clients sometimes call us with situations so specific that no forum, no YouTube tutorial, and no Google search can provide an answer.
That’s when the intervention of an experienced HVAC technician, on-site, becomes crucial. At AirGreen, we’ve seen it all. Here’s a collection of odd cases we’ve encountered throughout Montréal, Laval, Longueuil, and surrounding areas — issues that only real-world experience can detect and resolve.
A heat pump that works… but doesn’t heat a specific room
📍 Real case – Rosemère, North Shore
The client had just installed a Fujitsu KZAH 18,000 BTU wall-mounted heat pump, perfectly suited for the size of the ground floor. The unit worked correctly, BTU capacity was sufficient, airflow was consistent… yet one room stayed freezing, even with the door open.
🔍 AirGreen diagnosis: After a thermal inspection, we discovered that an old forced-air return duct (from a retired electric furnace) was causing heat loss into the crawlspace. We sealed the duct and added a small air transfer fan — the issue was resolved within 48 hours.
A dripping sound… that never happens during testing
📍 Gree Extreme 12,000 BTU installation in Longueuil
The client reported a constant dripping sound inside the wall at night. But during our tests, no sound could be heard. The indoor unit was level, the drain was functioning, and there was no backup.
🔧 Solution: When we inspected at night with the client, we found the noise only occurred when the outdoor temperature dropped below -12°C. It turned out to be condensation forming on an uninsulated refrigerant line inside the wall — it would freeze and then thaw. Replacing that section of pipe with reinforced insulated tubing eliminated the noise entirely.
A remote control that changes settings on its own
📍 Sharp ZU1 heat pump in Saint-Hubert
A client complained that her wall-mounted heat pump was switching modes by itself, without anyone touching the remote. Every night, it changed from heating to fan mode — sometimes even to “dry.”
🔍 After several attempts, we discovered the client had two Sharp remotes in the house, for two different units, operating on similar frequencies. Pressing a button in the basement was also triggering changes in the upstairs unit.
💡 Solution: We reprogrammed the remotes to different channels (a lesser-known but possible feature on some Sharp ZU1 models).
An outdoor unit that ices up… but never during inspection
📍 MIDEA25 installation in Laval
The unit worked perfectly during our visits. But according to the client, early in the morning, the outdoor unit was completely frozen, and indoor airflow was weak.
🧊 Hypothesis confirmed using an outdoor security camera: the unit wasn’t entering defrost mode during specific time slots. We updated the control board firmware and adjusted the defrost cycle. No issues since.
A burning plastic smell in cooling mode
📍 Montréal-Nord – Gree Lomo heat pump
A client complained of a burning plastic smell when using the heat pump in cooling mode. Everything looked clean: filter, coil, drain, motor…
🔬 After fully dismantling the unit, we found a small piece of plastic bag that had been sucked in during installation and was stuck near the fan. At low temps, the plastic would stiffen and rub against the motor blades.
✔️ Removed the fragment + full inspection = no more smell.
A room that overheats even though the heat pump is off
📍 Beaconsfield – Fujitsu 24,000 BTU installation
The client claimed that a guest bedroom was becoming abnormally warm, even though the heat pump was completely turned off. No airflow was active.
🧠 After investigation, we discovered that the piping passed behind the wall of that room. Thermal conduction from the refrigerant lines (embedded in the wall) was heating the drywall continuously, even when the compressor wasn’t running.
🛠️ Solution: We insulated the refrigerant lines with double-layer thermal sleeves in the exposed wall sections.
A brand-new heat pump… that smells bad at every restart
📍 Gree Sapphire installation in Sainte-Julie
A client noticed a musty smell every time the wall-mounted heat pump restarted automatically.
🔍 Diagnosis: After testing, we found that the unit was perfectly level, but it had been installed in a space with very little natural airflow, causing condensation to linger in the coil. We slightly tilted the unit toward the drain and added a humidity exhaust mini fan on a timer.
Result: problem solved, smell gone.
Conclusion: What Google can’t see, we detect on-site
Forums, YouTube videos, and search engines offer useful advice, but some anomalies require sharp on-the-ground experience and local technical know-how.
At AirGreen, our technicians work daily throughout Montréal, Laval, Longueuil, the North Shore, and the South Shore to resolve strange, unique, or invisible issues that online guides simply can’t diagnose.
For every service call, we analyze not only the equipment, but also the installation context, environment, user habits, and local climate conditions. That’s what makes us reliable and effective.