A typical winter intervention for AirGreen in Montreal
On a frigid January morning, our AirGreen team was dispatched to the Rosemont–La Petite-Patrie neighborhood of Montreal for a service call on an Ameristar wall-mounted heat pump . The owner of a red brick duplex reported that his unit was no longer heating properly, despite recent maintenance by another contractor.
The outdoor unit, installed on a galvanized steel wall bracket, was already showing signs of frost buildup—a telltale sign of a defrosting problem. This time of year is especially common: ambient humidity and temperature fluctuations around 0°C can easily disrupt the normal cycle of a wall-mounted heat pump.
Diagnosis: a blocked defrost cycle
Upon arrival, we performed a thorough inspection of the Ameristar unit. Upon verification, the R-410A refrigerant pressure was within normal limits, but the outdoor fan would not engage during the defrost phase. This symptom is typical of a faulty defrost sensor or a control board issue .
By observing the machine's behavior, we quickly confirmed that the system was attempting to enter defrost mode, but the temperature sensor was sending an incorrect reading. As a result, the compressor continued to run while frost persisted on the coil, significantly reducing airflow and, consequently, heating efficiency.
Intervention: sensor replacement and complete maintenance
Our technician took the following steps:
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Power supply cut-off to ensure safe intervention.
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Removing the side panel of the Ameristar outdoor unit.
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Removal and replacement of the defrost sensor with an original part supplied by our distribution partner.
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Complete cleaning of the coil to remove any buildup of ice and dirt.
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Restart the system and check the automated defrost cycle.
After these interventions, the heat pump restarted normally. In less than 10 minutes, we were able to observe a functional defrost cycle , followed by a return to a stable heating mode with a hot air flow of 41°C.
Prevention: Tips for optimal performance in winter
During our interventions, we always take the time to advise our customers on good winter maintenance practices . In the case of this Ameristar heat pump, we recommended:
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Never turn off the device completely during the winter, even during periods of prolonged absence.
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Maintain a clearance of at least 30 cm around the outdoor unit to promote air circulation.
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Schedule a complete annual maintenance before the cold season to check sensors, pressures and electrical connections.
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Install a specialized snow shelter if the unit is exposed to significant accumulations.
With these precautions, the life and performance of the system can be greatly extended—a lasting investment in home comfort and energy efficiency.
Result: comfort restored and efficiency regained
At the end of the repair, the interior temperature of the duplex returned to a comfortable level, and the owner regained the quiet, consistent operation typical of Ameristar systems. Electricity consumption also decreased after a few hours, proving that the heat pump was returning to its original efficiency.
This type of intervention perfectly illustrates AirGreen 's mission: to offer reliable, fast and transparent HVAC service , based on precise diagnostics and lasting repairs.
AirGreen expertise: Ameristar, but also all the major brands
Our certified technicians work on all major brands of wall-mounted heat pumps: Ameristar, Fujitsu, Midea, Gree, Sharp, Goodman, Bosch, Trane, Hitachi , and many others. Each repair follows a rigorous protocol: complete diagnosis, replacement of defective parts with original components, and verification of energy efficiency.
Whether you are in Montreal, Laval, on the North Shore or the South Shore , AirGreen is your trusted partner for all your HVAC repair and maintenance needs.
Technical details of the intervention
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Device Type : Ameristar Wall-Mounted Heat Pump (R-410A)
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Problem found : Defective defrost sensor
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Solution applied : Replacement of the sensor + cleaning of the coil
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Location : Rosemont–La Petite-Patrie, Montreal
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Result : Heating restored, defrost cycle functional, optimal performance
AirGreen: year-round comfort, guaranteed
Every service call is an opportunity for us to demonstrate our expertise and commitment to our customers. With certified technicians , genuine parts , and professional support , AirGreen ensures the performance and longevity of your HVAC system, summer and winter.