How to handle a wall-mounted air conditioner failure during a heatwave: practical tips for Montreal and surrounding areas
When a heatwave hits Montreal, Laval, Longueuil, or even the North Shore and South Shore, a broken wall-mounted air conditioner quickly becomes more than just an inconvenience—it becomes an emergency. At AirGreen, we understand how crucial a comfortable indoor temperature is for families, seniors, and children, especially when temperatures soar past 30 degrees. In this article, we’ll guide you step by step on what to do if your air conditioner stops working in the middle of summer, with concrete advice, mistakes to avoid, and the most effective solutions based on our field expertise in HVAC installation and maintenance across Greater Montreal.
Recognizing early signs of failure: don’t wait until your unit completely stops working
Before your wall-mounted air conditioner completely breaks down, some warning signs may signal an upcoming issue. As an experienced HVAC contractor, we recommend watching out for these symptoms:
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The unit is blowing warm air despite the settings
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An unusual increase in electricity consumption
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Strange noises or excessive vibrations
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Indoor humidity no longer feels controlled
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Blinking lights on the indoor or outdoor unit
If you notice any of these signs, we suggest contacting us before the unit fully stops working. This often helps avoid extended service interruptions during peak heat periods.
Step 1: Check the basics before panicking
Once the breakdown occurs, it’s essential to stay calm. Some basic checks can sometimes solve the issue without needing technical intervention:
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Make sure the circuit breaker hasn’t tripped: This can happen during a power surge caused by using multiple appliances at once.
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Clean or inspect the air filter: A clogged filter can prevent the unit from operating properly.
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Check the remote control or wall-mounted thermostat: Sometimes, a dead battery can cause communication failure.
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Listen to the outdoor compressor: If it's completely silent, it may indicate an electrical or mechanical problem.
If none of these basic checks solve the issue, it’s time to move on to the next step.
Step 2: Avoid common mistakes that can make the situation worse
When the heat becomes unbearable, it's tempting to try fixing the unit yourself. Here are some things you should absolutely avoid:
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Never open the wall-mounted or outdoor unit unless you’re trained: This can worsen the problem or expose you to electrical hazards.
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Avoid placing a fan on the outdoor unit’s motor hoping to “cool it down”: this does nothing and can cause damage.
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Do not use sharp tools to “clean” the outdoor coil fins.
At AirGreen, we’ve often had to step in after clients attempted DIY repairs that ended up making the situation more complex and costly.
Step 3: Call certified HVAC professionals
In the Greater Montreal area, AirGreen is known for its fast response times and expertise with all types of wall-mounted heat pumps and air conditioners (Fujitsu, Gree, Sharp, Daikin, LG, etc.).
When you contact us:
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We conduct a thorough on-site diagnosis, even during heatwaves, thanks to our mobile teams available across Montreal, Laval, Longueuil, North Shore, and South Shore.
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Our technicians inspect your entire system: indoor and outdoor units, condensate line, control boards, fans, sensors, refrigerant level.
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We then offer you fast and transparent solutions, including advice on repair, refurbishment, or replacement if needed.
Real case: urgent intervention in Laval during a major heatwave
Last July, during a heatwave, a family in Chomedey, Laval, called us urgently. Their 12,000 BTU Fujitsu wall-mounted air conditioner, installed 8 years prior, had suddenly stopped working. After a quick diagnostic, our team identified a burnt capacitor in the outdoor unit—a common issue during thermal overloads.
Result:
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Full repair completed within 3 hours of the call
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Immediate return to indoor comfort
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Advice provided on future replacement with a more energy-efficient unit eligible for Hydro-Québec grants
Step 4: Prevent future breakdowns with regular HVAC maintenance
Once the issue is resolved, the key is to prevent it from happening again. At AirGreen, we strongly recommend annual preventive maintenance, ideally before summer begins. This service includes:
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Deep cleaning of filters, coils, and condensate tray
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Checking refrigerant levels
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Thermostat calibration
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Electrical component inspection
This approach helps extend your system’s lifespan and avoid unexpected costs during critical periods.
Grants and replacements: thinking long term
If your unit is old or experiencing frequent issues, it might be time to consider a replacement. The good news: several government grants are currently available for the installation of high-efficiency units:
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Hydro-Québec’s LogisVert Program: Up to $2,172 depending on model and capacity
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Additional federal subsidies
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Low-interest financing available through partner institutions
Our teams guide you through every step—from estimate to grant application submission.
Why trust AirGreen if your air conditioner breaks down during a heatwave in Montreal?
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Quick response during heat emergencies
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Certified technicians for all brands
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Montreal-based customer service, always reachable
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Real-world experience with thousands of successful installations and repairs
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Local expertise: we understand the unique climate needs of every area—whether you’re in Brossard, Boisbriand, or Saint-Hubert
In conclusion: a heatwave breakdown doesn’t have to become a disaster
At AirGreen, we know that every hour matters when your wall-mounted air conditioner fails during summer. Thanks to our fast interventions, proven expertise in HVAC repair, and personalized support, you’ll quickly regain comfort—without stress or surprises.
Contact us today for fast, transparent, and professional service across Montreal, Laval, Longueuil, South Shore, and North Shore.