An aging wall-mounted air conditioner that stops blowing cold air
At AirGreen , our technicians are often called upon to work on Fujitsu wall-mounted systems that have been installed for over ten years. These devices, known for their reliability, however, eventually show signs of wear over time. This is exactly what we observed during a service call in Ville Mont-Royal , where a customer reported that their Fujitsu wall-mounted air conditioner was no longer producing cold air despite the fan being on.
Initial diagnosis: warm airflow and an inactive compressor
Upon arrival, we noticed that the indoor unit seemed to be operating normally: the shutters opened, the fan ran, and the remote control responded. However, no cold air was felt, even after several minutes of waiting. This symptom pointed our diagnosis towards:
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a communication problem between the indoor and outdoor units;
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a lack of refrigerant due to a slow leak;
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or a faulty electronic card preventing the compressor from starting.
Our technicians therefore carried out a complete inspection of the communication circuit and the outdoor condenser . After checking the voltages and control signals, we found that the compressor was not receiving the start command, despite a stable supply voltage.
Step 1: Analysis of the electronic circuit
We opened the indoor unit cover to check the Fujitsu control board . Using our multimeter, we identified a burnt resistor on the power module, a typical sign of a previous power surge. This failure prevents the board from transmitting the signal to the compressor start relay.
We then confirmed that the outer board was intact, allowing us to target the issue to the inner main board.
Step 2: Replacing the faulty electronic board
Once the fault was confirmed, we replaced the control board with a genuine Fujitsu part compatible with this series of wall-mounted air conditioners. This delicate operation requires:
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Complete shutdown of the system.
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The careful removal of connectors and sensors.
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Installation of the new card with verification of polarities and wiring.
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The gradual restart of the system , ensuring synchronization between the two units.
After reinstallation, the system returned to normal operation. The compressor started, the blowing temperature dropped to 8°C , and the customer immediately felt the difference.
Step 3: Final checks and preventive maintenance
To avoid future problems, we have also:
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Cleaned the air filters and coils of the indoor unit .
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Checked the condensate drain to make sure it was not clogged.
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Measured the pressure of R-410A refrigerant , confirming that it was within the manufacturer's specifications.
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Tested power consumption to ensure no components were drawing excessive current.
The system passed all tests successfully.
Lessons Learned: Why This Failure Is Common on Older Fujitsu Units
Fujitsu wall units from 2010–2015 have a control circuit that is sensitive to electrical fluctuations . In older homes without surge protection, the boards can be damaged as a result of fluctuations in mains voltage.
This is why we strongly recommend installing a dedicated HVAC protection circuit breaker , especially in residential areas of Montreal, Laval, Longueuil, the North Shore and the South Shore , where electrical stability varies depending on the area.
Our tips for extending the life of your wall-mounted air conditioner
To avoid breakdowns like this, AirGreen recommends that all owners:
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Have their wall system inspected once a year , before the summer season.
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Clean the filters every 4 to 6 weeks.
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Install a surge protector on the HVAC circuit.
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Leave the system in “ventilation” mode for a few minutes after air conditioning to evacuate residual humidity.
These simple actions extend the life of the system and maintain optimal energy efficiency.
Result: comfort restored and system stabilized
Following our intervention, the client in Ville Mont-Royal regained immediate comfort and a quiet system . The Fujitsu wall-mounted air conditioner returned to its original performance, guaranteeing efficient cooling throughout the summer.
This type of repair perfectly illustrates the expertise of our AirGreen team : combining precise diagnosis, targeted replacement and preventive maintenance to provide lasting results.
Our technicians are trained to work on all major brands— Fujitsu, Sharp, Gree, Midea, Lennox, Goodman, Trane, Bosch, Comfortmaker —throughout the metropolitan area.
In conclusion
At AirGreen , every service call is handled with the same rigor: comprehensive analysis, lasting solutions, and customer satisfaction . If your Fujitsu wall-mounted air conditioner is showing signs of weakness, don't wait for the next heat wave . Our teams are available quickly in Montreal, Laval, Longueuil, and on the North and South Shores to bring your HVAC system back to life.