In a condo in Rosemont–La Petite-Patrie , we received a call with a very common complaint: "The heat pump is working, but it's no longer comfortable." The wall unit displayed the air conditioning mode (snowflake symbol) and a set temperature of 16°C , yet the room remained lukewarm at times, with an uneven airflow and performance that varied throughout the day.
On site, our AirGreen technician quickly confirmed that it was a Tosot wall-mounted heat pump (mini-split) and began by objectively assessing the situation with simple but very telling measurements: outlet air temperature , airflow stability, condition of the damper and heat exchanger, and then checking the operating parameters. The photo taken during the service call also shows a temperature reading taken with an infrared thermometer, a practical field check that allows for immediate verification that the unit is actually producing consistent cooling.
Observed symptoms: unstable performance and uneven comfort
Before dismantling anything, we took the time to listen to the client and cross-check the clues:
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The cooling effect was considered "less severe" than before, especially during the hottest hours.
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Airflow that sometimes seemed reduced
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The impression is that the device is working hard (for a long time) without achieving the expected comfort.
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In some similar cases, we also see the appearance of odor, unusual condensation, or the beginning of frost — all signs that we systematically check
These symptoms do not automatically point to a single cause. On a Tosot (often very reliable), the most frequent scenarios are: fouling (filters/evaporator), partially obstructed drainage, drifting temperature probe, disrupted fan speed, or refrigerant charge affected by a micro-leak (rarer, but to be checked seriously).
AirGreen diagnosis: we eliminate the causes in the right order
Our approach is deliberately methodical: we start with what most influences daily performance, then we move towards refrigeration.
1) Inspection and access to the internal heat exchanger
The unit was opened (panel lifted), which allowed us to verify:
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Condition of the filters (fine dust typical of condos)
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State of the evaporator (fins that can become charged and "stifle" heat exchange)
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Actual flow rate : if the air doesn't flow well, the machine may cool "on paper", but not in the room
2) Checking drainage and condensation
A partially blocked drain can cause poorly managed condensation, sometimes excessive humidity at the wall outlet, and in the long run, a loss of performance (not to mention the risk of water damage). Therefore:
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Controlled the slope and flow
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Cleaned/sanitized the pathway if necessary
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Checked that there was no return of odors or backflow
3) Probe and regulation control
On a wall-mounted heat pump, a faulty temperature sensor can disrupt the modulation: the machine "thinks" it has reached the setpoint or starts to oscillate. Therefore, the consistency of the readings, the sensor's location, and the stability of the control system were checked.
4) Refrigeration control and performance validation
Once the "air" section is optimized, the cooling performance is validated: pressures, stability, anomaly detection, and temperature consistency (return/supply). The measurement visible in the photo (supply air temperature) serves precisely to confirm that the unit delivers sufficiently cold air in a stable manner, which is essential for maintaining consistent comfort.
Intervention: complete overhaul (cleaning + correction of the causes)
In this case, the repair consisted of restoring the system to its optimal operating condition by combining:
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Complete cleaning of elements that directly affect flow rate and heat exchange (filters, exchange zone, accessible sections)
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Checking and securing drainage (smooth flow, no obstructions, no residual moisture)
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Parameter check and validation that the machine modulates correctly in air conditioning
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Performance measurements after intervention to confirm stable cold air delivery and regular operation
The goal is not just "to get it working again", but for the heat pump to do the job it is supposed to do : cool down quickly, maintain the setpoint without straining, and distribute the air comfortably.
Result: comfort restored and customer reassured
After the repair, the Tosot wall-mounted heat pump returned to normal operation: improved airflow, cooler and more consistent airflow, more coherent cycles, and above all, an immediate feeling of comfort. The customer also gained peace of mind: they received a clear explanation of what was affecting performance and how to prevent it from happening again (filter maintenance, warning signs to watch for, and recommended maintenance frequency).
Why is this type of repair common in condos in Montreal?
In areas like Rosemont–La Petite-Patrie, installations often run frequently during the summer, exposed to urban dust, humidity fluctuations, and intensive use. A wall-mounted unit can then lose efficiency without actually "breaking down" in the strictest sense. This is precisely where our AirGreen approach makes a difference: concrete diagnosis, targeted actions, and validation through measurements .