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Réparation d’une thermopompe murale ComfortStar à Rosemont–La Petite-Patrie
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Repair of a ComfortStar wall-mounted heat pump in Rosemont–La Petite-Patrie

A quick service call to a Montreal apartment in the middle of summer

When one of our clients in Montreal 's Rosemont–La Petite-Patrie neighborhood contacted us one July afternoon, it was over 30°C outside. Their ComfortStar wall-mounted heat pump , installed on a painted brick wall, hadn't been blowing cold air for two days. At AirGreen , we know that every minute counts when an air conditioning system breaks down during a heatwave, so our team came out the same day.

Diagnosis: A blocked interior fan and a faulty thermal sensor

Upon arrival on site, our technician noted that the indoor unit—a ComfortStar mini-split wall-mounted model —appeared to be intact, but that no airflow was coming out despite the noise of the outdoor compressor.

After opening the hood, the problem quickly appeared:

  • A buildup of dust and lint was partially blocking the tangential fan.

  • The evaporator temperature sensor (thermistor) was sending incorrect readings, preventing the electronic board from allowing ventilation.

These two failures combined explained why the unit would start, but automatically shut down after a few minutes.

Repair steps: cleaning, replacement and recalibration

Our technicians have undertaken a complete upgrade procedure :

  1. Complete disassembly of the casing and removal of the internal fan.

  2. Careful cleaning of the blades and coil using a biodegradable detergent.

  3. Replaced the temperature sensor with an original ComfortStar model to ensure an accurate reading.

  4. Checking the control wiring and the electronic card, without traces of oxidation.

  5. Refrigerant circuit pressure test (R410A) — meets specifications.

  6. Reassembly and final performance test .

After 10 minutes of operation, the measured air outlet temperature was 8.7°C , confirming optimal performance.

Result: restored efficiency and comfort regained

Thanks to this intervention, the client was able to enjoy immediate comfort again.
The ComfortStar heat pump has resumed smooth, quiet and precise operation, with better distribution of fresh air in the main room.

We also scheduled an annual maintenance visit , to prevent further dust buildup on the internal sensors—a common problem in Montreal's urban apartments.

Maintenance advice given to the customer

Before leaving the premises, our AirGreen technician shared some practical tips:

  • Clean filters every 4 to 6 weeks during the summer.

  • Avoid air fresheners or aerosols near the unit, which can clog the sensors.

  • Schedule preventive maintenance before the start of each warm season to avoid sudden breakdowns.

Simple but regular maintenance guarantees the longevity and performance of any wall-mounted heat pump.

AirGreen: your HVAC partner in Montreal and on the North Shore / South Shore

Whether you are in Montreal, Laval, Longueuil, on the North Shore or the South Shore , our certified technicians respond quickly for any repair, maintenance or HVAC installation .

At AirGreen , we put our expertise at the service of your comfort, whatever the brand — ComfortStar, Gree, Midea, Fujitsu, Sharp, Trane and many others.

Each intervention is carried out with rigor, transparency and respect for the standards of the Régie du bâtiment du Québec (RBQ) .