A compressor stopped in the middle of winter: a typical case in Sainte-Julie
At AirGreen , our teams work year-round to ensure the proper functioning of HVAC systems throughout Greater Montreal. This service call in Sainte-Julie , on the South Shore , involved a wall-mounted heat pump installed on a house with green siding, typical of the region's quiet residential neighborhoods. The customer contacted us after noticing that the outdoor unit was no longer producing heat despite the indoor fan audibly starting.
Diagnosis: an intermittent electrical failure
When our technician arrived, the first step was to check the power supply to the outdoor unit. It seemed to be operating intermittently—a common behavior when the protective circuit breaker or wiring experiences voltage fluctuations. After opening the control box, a visual inspection identified a poor contact in the service circuit breaker terminal block .
This type of failure, often caused by winter humidity, can prevent the compressor from starting, even if the fan is running properly.
To confirm the diagnosis, we proceeded to:
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a voltage measurement at compressor start-up ,
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a continuity test of the power wiring,
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and a check of the communication between the indoor and outdoor unit via the control board.
As a result, the voltage fluctuated below the required limit, causing the compressor to automatically shut down for safety reasons.
Repair: wiring restoration and electrical stabilization
We have made the following corrections:
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Complete replacement of the outdoor circuit breaker with a waterproof protection model that complies with CSA standards.
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Re-establish electrical connections using heat shrink terminals to prevent moisture infiltration.
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Cleaning and resealing the cable gland connecting the heat pump to the wall.
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Complete system test under load to confirm current and compressor stability.
Once the repair was completed, the heat pump resumed normal operation, with a constant flow of hot air and stable electricity consumption .
Performance verification and optimization
We completed the intervention with:
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a check of refrigerant pressures ;
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an automatic defrost test (essential in cold weather);
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and a check of the insulation of the copper lines , which had recently been redone with white thermal protection.
The unit has thus regained its optimal performance, without abnormal noise or excessive vibration.
Prevention: maintenance tips to avoid winter breakdowns
Our experts remind you that a wall-mounted heat pump installed outside must be protected against:
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snow accumulations under the condenser ,
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water infiltration into the electrical box ,
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and cold-related voltage fluctuations .
At AirGreen , we recommend biannual preventative maintenance , in spring and fall, to avoid this type of electrical failure that can occur at any time.
Final result: restored comfort and increased reliability
Thanks to a quick and methodical intervention, the wall-mounted heat pump in this Sainte-Julie residence is fully operational again. The client enjoys stable heating, even on the coldest nights, and has chosen to sign up for our AirGreen Plus maintenance program to ensure the longevity of their unit.
This repair illustrates our approach: technical rigor, transparency and lasting performance .
Whether in Montreal , Laval , Longueuil , on the North Shore or the South Shore , AirGreen remains the trusted choice for any repair, maintenance or installation service for residential and commercial HVAC systems.