The comfort of your home depends largely on the proper functioning of your wall-mounted air conditioner. In Montréal, Laval, Longueuil, on the North Shore and the South Shore, seasonal temperature shifts make these systems essential. Yet many homeowners overlook the early warning signs of a failing wall-mounted AC unit. At AirGreen, our on-the-ground experience has helped us diagnose and repair hundreds of malfunctioning wall-mounted air conditioners, and we know exactly what to watch for.
Here are the three most common signs that your unit may be breaking down — and why ignoring them can lead to bigger problems.
Noticeable Drop in Performance: The Air Isn’t Cooling Like It Used To
One of the first symptoms we regularly encounter during our HVAC maintenance calls in Montréal and surrounding areas is a clear decrease in cooling performance. If you notice that the air coming out of your system isn’t as cool as it once was, or if it takes longer to reach your desired temperature, this could indicate:
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A heavily clogged filter or evaporator coil.
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A refrigerant leak (often R-32 or R-410A, depending on the model).
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An aging or overloaded compressor.
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A poorly calibrated thermostat.
At AirGreen, during our interventions in homes across Laval and Longueuil, we’ve found that even reliable models like the Fujitsu KZAS 12,000 BTU or the Gree Lomo can show these symptoms after several seasons without proper maintenance.
Our Concrete Recommendations:
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Don’t wait to call a professional as soon as you notice a drop in performance.
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Have the refrigerant levels checked.
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Schedule annual preventive maintenance in spring to avoid breakdowns in summer.
Unusual Noises: Vibrations, Clicking, or Rumbling
A wall-mounted AC unit should operate almost silently. If you suddenly hear metallic sounds, knocking, excessive vibrations, or low rumbling, something is definitely wrong. We were recently called to a condo in Boisbriand (North Shore) where a Sharp ZU1 18,000 BTU made a deep rumble every time it turned on.
Our diagnosis revealed:
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A bent fan blade caused by accidental impact.
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Loose internal screws.
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Early-stage blower motor failure.
In other cases, noise issues can stem from improper leveling of the outdoor unit, or poorly secured wall brackets, as we saw during an installation in Saint-Bruno (South Shore).
What You Should Do Immediately:
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Turn off the unit to prevent further damage.
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Book an inspection with a certified AirGreen technician.
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Don’t open the unit yourself — the components are sensitive and can be easily damaged.
Water Leaks or Excessive Moisture Around the Indoor Unit
A properly maintained wall-mounted air conditioner should never leak or create excess moisture. If you see puddles on the floor under the indoor unit or dripping water, this may be due to:
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A clogged condensate drain (often blocked by dust or mold).
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A malfunctioning condensate pump — common in high-rise apartments in Montréal.
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Improper leveling of the unit during installation.
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Ice buildup on the evaporator caused by abnormal pressure in the refrigerant circuit.
We recently repaired an installation in Saint-Léonard, where a Toshiba 15,000 BTU wall-mounted AC was improperly installed: the drain wasn’t positioned for proper water evacuation. The result: wall seepage and mold growth.
Typical Interventions by AirGreen:
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Complete condensate drain cleaning using specialized tools.
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Realignment of the indoor unit to ensure correct slope.
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Replacement or repair of the condensate pump.
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In-depth analysis of the refrigerant circuit to detect anomalies.
Why You Should Call AirGreen at the First Sign of Trouble
We don’t just diagnose issues: we provide long-term solutions tailored to each residential or commercial setup. Thanks to our wide service coverage — from Montréal to Terrebonne, including Boucherville and Lavaltrie — we respond quickly with experienced and certified technicians.
Our interventions rely on advanced tools, proven expertise, and complete transparency in diagnosis and repair. Every service call is an opportunity to advise you on:
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The energy performance of your current system.
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Whether a replacement is a smarter long-term option.
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Available grants (like Hydro-Québec’s LogisVert Program).
When to Replace Instead of Repair?
Sometimes, repair is no longer the most sensible option, and it’s time to replace your wall-mounted air conditioner. We generally recommend replacing the unit when:
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The system is over 10 years old.
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Breakdowns are frequent.
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Repair costs exceed 30% of the price of a new unit.
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The model no longer complies with new refrigerant regulations (switch to R-32 or R-454B).
In these cases, AirGreen supports you in choosing and installing a new energy-efficient system, such as Bosch BIVA, Fujitsu KZAS, or Gree Sapphire models, all of which qualify for current grant programs in Longueuil, Laval, and the greater Montréal area.
A Local Commitment, Tangible Results
Our numerous interventions in cities like Repentigny, Brossard, Rosemère, or Verdun have helped hundreds of families regain their comfort. Every HVAC installation or wall-mounted air conditioner repair is a chance to show our professional thoroughness and attention to detail.
AirGreen is more than just an installer — we’re a trusted partner for all your heating, ventilation, and air conditioning needs.