When a wall-mounted heat pump stops working during the harshest days of a Québec winter, every second counts. A sudden failure can quickly compromise your home’s thermal comfort—especially in exposed areas like Montréal, Laval, Longueuil, the North Shore, or the South Shore. In a moment of panic, some instinctive actions might actually make things worse, cause irreversible damage, or even void your unit’s warranty. At AirGreen, we receive distress calls every winter. Drawing from our real-world experience, here are the 5 most critical mistakes to avoid immediately if your wall-mounted heat pump breaks down in winter.
Why Wall-Mounted Heat Pump Failures Are More Critical in Winter
Québec’s winter climate is extreme. When temperatures drop below -15°C, even the best high-efficiency heat pumps are pushed to their limits. A breakdown—even a short one—can:
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Freeze indoor piping
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Cause condensation and excess humidity
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Lead to costly energy bills if a backup system kicks in
Mistakes aren’t an option: one wrong move can be expensive.
1. Never Try to Manually Defrost the Outdoor Unit
This is hands down the most common mistake. If you notice ice buildup on the outdoor unit—especially on the coils—do NOT use a sharp object, broom, or hair dryer to remove it. That ice is usually part of a normal automatic defrost cycle built into the heat pump.
Real case in Laval: a homeowner punctured the coils while trying to “clear the ice.” Result: full coil replacement and warranty voided.
AirGreen Tip: let the unit complete its defrost cycle. If the ice is still present after 90 minutes, call our technical support.
2. Avoid Restarting the Unit Repeatedly
When a wall-mounted heat pump breaks down, the natural instinct is to turn it off, back on, adjust settings, switch from heat to fan mode… But this disrupts the compressor and can trigger a safety lockout.
Installation in Longueuil: a customer restarted her Gree unit 7 times in 10 minutes. The system went into a hard error code (safety mode), requiring an emergency service call.
AirGreen Tip: if your system doesn’t restart properly after a glitch or strange behaviour, turn it off for 10 to 15 minutes, then try powering it back on once.
3. Do Not Cover the Outdoor Unit
Some people try to protect the outdoor unit with a tarp or cover to block snow. Huge mistake. A wall-mounted heat pump runs year-round, even during deep winter. Covering it will:
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Block airflow
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Cause the motor to overheat
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Damage electronic components
Installation in Saint-Eustache: after placing a plastic tarp over the unit, the internal temperature reached 68°C, damaging the control board.
Correct approach: keep snow cleared around the unit, but never place anything directly on it.
4. Never Pour Hot Water or Salt on the Unit
When snow turns into ice around the base of the outdoor unit, some try to pour hot water or salt to melt it. Thermal shock or chemical reactions can severely damage internal components and accelerate corrosion.
Service call in Montréal: a customer poured a bucket of boiling water on the unit. This cracked the drain pan and misaligned the fan.
AirGreen Solution: if the base is frozen, we recommend a low-pressure warm air cleaning, which our technicians perform using professional-grade tools.
5. Never Force a Mode or Use an External Thermostat Without Verifying
Some homeowners connect their heat pump to a standard wall thermostat thinking it will improve control. But if not fully compatible, it can interrupt the defrost cycle, send false signals, or shut down the unit altogether.
Case in Terrebonne: a Bosch heat pump stopped heating because the wall thermostat blocked it from entering defrost mode. Result: major frost buildup and total shutdown.
AirGreen Recommendation: always use the manufacturer-supplied remote or interface, or consult us before installing a smart thermostat.
What AirGreen Recommends If Your Heat Pump Breaks Down in Winter
If your wall-mounted heat pump stops working during winter, follow this recommended protocol:
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Take note of the symptoms: flashing lights, sounds, error codes, outdoor temperature
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Shut off the unit, wait 10 to 15 minutes
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Inspect visually without touching anything: excess ice, blockages, strange noises
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Call our AirGreen technical team: we prioritize winter emergency calls
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Don’t adjust the settings, and avoid multiple restarts
What AirGreen Does During an HVAC Emergency in Winter
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Rapid response (under 24 hrs) in most cases across Montréal, Laval, Longueuil, North Shore, and South Shore
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On-site diagnostics, including cycle analysis and electronic checks
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Controlled defrosting, filter cleaning, fan inspections
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Immediate repairs if parts are available in our mobile fleet
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Express replacement for defective or out-of-warranty equipment
Conclusion: Act Methodically, Never in Panic
When it’s -20°C outside and your heat shuts off, panic is understandable. But those are the moments when rash actions can do the most harm. Modern wall-mounted heat pumps are complex, precise systems that require professional intervention to maintain performance, durability, and safety.
At AirGreen, we’re here to advise, act quickly, and help you get your comfort back—without making things worse.
Need urgent service for your wall-mounted heat pump this winter? Contact AirGreen right away. Our teams are active throughout Greater Montréal and can respond fast—even in extreme cold.