A simple wall-mounted air conditioner can hide many unexpected traps. In Montréal, Laval, Longueuil, the North Shore and the South Shore, we receive panic calls every summer. What do these clients have in common? They tried to repair their air conditioning system themselves… before things went terribly wrong. At AirGreen, we believe it’s essential to share these stories to help others avoid the same costly — and sometimes dangerous — mistakes.
When DIY air conditioner repairs turn into a really bad idea
The idea of fixing your own wall-mounted air conditioner might seem like a money-saver at first. But in reality, without the right tools, knowledge of refrigeration, and electrical safety training, the consequences can be serious: worsened breakdowns, risk of injury, voided warranties, or in extreme cases, fires.
Here are five real stories that happened in the Greater Montréal area that we personally handled. They show just how badly a DIY repair can go — and why calling professionals like us is often the only real solution.
1. Heat exchanger accidentally punctured – Laval, Chomedey neighborhood
A homeowner noticed that his Fujitsu wall-mounted air conditioner (model 12RLFW1, 12,000 BTU) was no longer blowing cold air. After browsing a forum, he decided to take apart the wall unit himself. While trying to "clean" the fins, he used a wire brush that was too harsh and accidentally punctured the evaporator, causing a massive leak of R-410A refrigerant.
➡️ Consequences:
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Complete refrigerant leak
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Irreversible internal damage
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Full unit replacement required
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Manufacturer warranty voided
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Final cost: $2,850 instead of a $180 professional maintenance visit
2. Short circuit and fire hazard – Longueuil, Vieux-Longueuil area
A DIY enthusiast attempted to replace the start capacitor of his Gree Lomo 18,000 BTU wall-mounted air conditioner. Without turning off the power, he accidentally touched two terminals on the circuit board. A spark ignited the insulation on the power wire.
➡️ Consequences:
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Short circuit and smoke release
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Fire department intervention
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Insurance company involvement
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Complete CVAC system shutdown
3. High-pressure cleaning disaster – Montréal, Rosemont
A client wanted to “do the right thing” and used a pressure washer on his Goodman central air conditioner’s outdoor unit. Unfortunately, water infiltrated the electrical circuits and sensors. The result: the control board and fan motor were damaged.
➡️ Consequences:
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Total system failure
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Replacement of two major components
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Over $1,200 in unnecessary repairs
4. Wrong replacement part installed – South Shore, Brossard
A client tried to replace a temperature sensor on his Haier Flexis heat pump with a part purchased online. Although the connector looked the same, the calibration was incorrect. The compressor ran continuously for 12 hours without stopping.
➡️ Consequences:
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Compressor overheating
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Skyrocketing electricity consumption
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Complete failure requiring a new compressor ($1,900)
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Loss of LogisVert subsidy eligibility
5. Illegal refrigerant refill – North Shore, Terrebonne
Thinking his unit was low on refrigerant, a homeowner purchased a canister of R-32 online and attempted a refill “the old-school way.” Not only was this done without a vacuum gauge, but the excess pressure cracked the compressor.
➡️ Consequences:
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Real risk of explosion
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Illegal release of gas into the environment
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Full replacement of the Mitsubishi Zuba 24,000 BTU system
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Intervention from Environment Canada for illegal refrigerant handling
Why are these mistakes so common?
Many people underestimate the complexity of modern CVAC systems. Every component — from the indoor unit to the refrigerant lines to the electronic boards — is precisely calibrated. Any untrained intervention can severely compromise home safety.
The hidden risks of DIY air conditioner repair
Here’s a list of common issues we see at AirGreen after amateur repair attempts:
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Incorrect initial diagnosis
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Handling refrigerant gases without certification (illegal)
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Use of improper tools
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Damage to welds and refrigerant connections
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Electrical risks: electrocution or fire
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Immediate voiding of the manufacturer’s warranty
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Ineligibility for government subsidies (Hydro-Québec, LogisVert, etc.)
How AirGreen handles these situations
At AirGreen, every CVAC maintenance or repair service starts with a full inspection by certified refrigeration technicians. We use professional diagnostic tools, original branded parts, and follow Québec’s safety protocols to the letter.
Our certified technicians operate across Montréal, Laval, Longueuil, the North Shore, and the South Shore. Whether it’s a repair, a refrigerant check, preventive maintenance, or a full wall-mounted AC installation, we guarantee professional work, fast service, and compliance with the highest standards.
Practical tips to avoid these mistakes
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Never open an air conditioner without cutting power
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Never try to recharge a system without proper certification
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Avoid non-original or online replacement parts
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Call a certified professional at the first sign of malfunction
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Never use high-pressure water on an outdoor unit
One simple solution: call us before things get worse
Calling AirGreen means peace of mind. Our teams are here to diagnose, repair or replace your air conditioning system with precision and transparency. In many cases, a proper repair can prevent the need for a full system replacement.
Still hesitating?
Let us inspect your wall-mounted air conditioner before it gets out of hand. A professional assessment today can save you thousands tomorrow.