A wall-mounted air conditioner stuck in cooling mode despite the heating request
A resident of Montreal's Rosemont–La Petite-Patrie neighborhood contacted us for an urgent service call : their Fujitsu wall-mounted air conditioner was no longer producing heat, despite the temperature being set at 24°C. In the midst of the fall transition, this outage was causing significant discomfort.
At AirGreen , we immediately dispatched a certified technician to diagnose and repair the unit.
First inspection: a cluttered interior and disturbed airflow
The indoor unit, installed high above wall shelves (as seen in the photo), had restricted air circulation .
The shelves were obstructing airflow, causing:
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A disturbed return of hot air , preventing the internal probe from correctly measuring the ambient temperature.
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Repeated short cycles , tiring the external compressor.
When I turned it on, the green light on the panel would come on, but the air conditioner would stay stuck in cooling mode , a potential sign of an electronic board or temperature sensor error .
Diagnosis: A communication problem between the indoor unit and the outdoor compressor
Thanks to our Fujitsu diagnostic instruments, we have identified:
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An error code “E0” , indicating a loss of communication between the two units.
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Fluctuating voltage at the external terminal block , a symptom of a main board slightly damaged by current variations.
The customer confirmed to us that he had experienced a brief power outage the previous week – a perfect context for this type of outage.
Repair steps: precision and electronic protection
Our AirGreen technicians undertook a complete repair in three phases:
1. Checking and securing the wiring
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Continuity test between terminals L, N, S.
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Cleaning and tightening electrical connections, often a source of micro-oxidation.
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Application of a protective dielectric gel to prevent moisture.
2. Replacing the communication card
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Removing the inner PCB board , responsible for the signal between the modules.
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Installation of an original Fujitsu card supplied by our certified warehouse.
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Quick reprogramming of synchronization parameters.
3. Reorganization of the space around the unit
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Recommendation to the customer to move the shelves to free up the airflow.
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Complete cleaning of the filter and temperature sensor.
Once everything was turned back on, the heating mode started immediately . The associated Daikin outdoor compressor returned to its nominal frequency, and the customer felt the heat in less than two minutes.
Result: restored comfort and stabilized consumption
At the end of the intervention:
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The blown air reached 41°C at the outlet of the wall unit.
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Communication between the modules remained stable at 230 V.
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The system has resumed quiet and smooth operation , as it originally did.
The customer was impressed with the speed of the diagnosis and the accuracy of the repair . We also recommended the addition of an AirGreen surge protector , specifically designed for inverter heat pumps and air conditioners.
AirGreen Expertise: Reliable and Certified Repairs
At AirGreen , our technicians are trained to work on the main brands on the market, including Fujitsu, Daikin, Gree, Midea, Sharp, Trane and Mitsubishi .
Each repair follows a strict protocol:
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Complete electronic diagnostics using specialized tools.
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Use of original parts only.
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Post-repair performance control (pressure, temperature, communication, consumption).
Our goal: to offer sustainable, effective and transparent interventions , throughout Montreal, Laval, the North Shore and the South Shore .
AirGreen Tips to Extend the Life of Your Wall-Mounted Air Conditioner
To avoid this type of breakdown in the future:
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Always install your unit in an open space , without shelves or curtains nearby.
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Schedule a complete maintenance in the spring and fall .
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Have the electronic card checked every 3 years to prevent oxidation.
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In the event of a power outage, unplug the unit for 5 minutes before restarting it.
These best practices can prevent up to 70% of electronic failures on Fujitsu wall systems.
Conclusion: another successful intervention by AirGreen
Thanks to a quick and methodical intervention, we restored the heating and reliability of the Fujitsu wall-mounted air conditioner in this apartment in Rosemont–La Petite-Patrie.
Once again, AirGreen demonstrates its commitment to quality, precision and customer satisfaction in the field of residential HVAC in Montreal and its surrounding areas.