An intermittent outage caused by an electrical connection problem
At AirGreen , we are often called out for intermittent breakdowns on residential HVAC systems. This is exactly the case with this Fujitsu wall-mounted heat pump installed on a duplex in La Prairie , on the South Shore of Montreal . The customer noticed that his heat pump worked perfectly some days, but would suddenly stop heating for no apparent reason.
The outdoor unit was installed on a wall combining brick and vinyl siding , a configuration typical of semi-detached dwellings. On the surface, nothing was amiss: the fan was running, there were no suspicious noises, and no errors were displayed on the remote control.
Diagnosis: unstable voltage at the outdoor unit
During our inspection, we immediately suspected a power supply problem. Using our multimeter, we measured the voltage at the input terminals: the voltage fluctuated between 170 V and 225 V , while it should remain at a stable 240 V.
After tracing the power line, our technician discovered a loose connection inside the wall junction box , just before the heat pump input. Natural vibrations from the compressor, combined with seasonal freeze-thaw cycles, had slightly loosened the neutral terminal . This micro-interruption was causing random system restarts.
Repair: securing and complete overhaul of the wiring
Once the cause was identified, we proceeded with the following steps:
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Complete power cut to secure the intervention.
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Opening the junction box and inspecting all connections.
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Replacement of the weakened connector with a waterproof compression model (exterior rated).
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Check grounding and tighten all main terminals.
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Hot voltage test after power-up: stable voltage at 239 V.
Once these adjustments were made, we restarted the Fujitsu heat pump and checked the behavior of the indoor unit: smooth start-up, constant hot air at 36°C at the outlet, and no voltage fluctuations detected during 20 minutes of continuous testing.
Recommended maintenance and prevention
To ensure the longevity of the system, we recommended to the customer:
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Annual preventive maintenance to check electrical connections and coil cleanliness.
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Installing a dedicated circuit breaker if multiple devices share the same line.
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Preventive replacement of the power cable if it shows signs of aging or excessive rigidity.
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A grounding check before each heating season.
Result: stability and performance restored
After our intervention, the heat pump resumed perfectly stable operation . The customer immediately noticed the difference: no more unpredictable restarts, constant heat and normal energy consumption.
We also took the time to explain to the owner the importance of good electrical contact on this type of highly sensitive electronic system. Fujitsu control boards are renowned for their efficiency, but they require stable voltage to operate optimally.
AirGreen expertise in La Prairie and on the South Shore
Whether it's Fujitsu, Midea, Sharp, Gree, Zephyr or LG , our certified technicians diagnose and repair HVAC systems throughout the greater Montreal area, from Brossard to Varennes and La Prairie .
At AirGreen, every service call is handled methodically and transparently :
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Accurate diagnosis before any intervention.
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Complete explanation of causes and solutions.
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Compliance with electrical and environmental standards.
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Post-intervention follow-up to ensure customer satisfaction.
Conclusion
This Fujitsu wall-mounted heat pump repair in La Prairie perfectly illustrates the difference between a simple apparent failure and a subtle electrical cause . Thanks to a rigorous diagnosis, our technicians were able to restore system stability, ensure the safety of the installation, and extend the life of the device.
At AirGreen, we combine experience, precision and customer commitment to provide impeccable HVAC service on the South Shore and throughout the greater Montreal area.