A precise and urgent service call
At AirGreen , we often receive calls for electrical or control board issues on Fujitsu wall-mounted air conditioners . This intervention, carried out in an apartment in the Côte-des-Neiges–Notre-Dame-de-Grâce sector of Montreal , perfectly illustrates the type of in-depth diagnosis our technicians perform when an indoor unit stops responding correctly to commands or displays erratic behavior.
Initial diagnosis: a faulty electronic card
Upon arrival, the customer reported that his Fujitsu wall-mounted air conditioner had stopped turning on and that no indicator lights were displayed on the front panel. The outdoor unit, however, showed no signs of starting.
Our technicians immediately carried out a complete electrical check , verifying:
-
Power supply to the dedicated circuit breaker.
-
The voltage at the input terminals of the indoor unit.
-
The wiring between the indoor unit and the control module.
Result: The power supply was intact, but the main control board located in the wall unit was visibly damaged, showing burn marks at the voltage regulator .
This type of failure is common during power surges or electrical fluctuations, particularly in older buildings in Montreal where network stability can vary.
A meticulous and safe repair
Complete disassembly of the front panel of the Fujitsu wall-mounted air conditioner confirmed the diagnosis. We carefully removed the control board, disconnected each connector, and checked the signal transfer between the temperature sensors and the main board .
Next, an original Fujitsu replacement board was installed, followed by a continuity and communication test with the infrared remote control.
Our precise steps:
-
Complete power cut to avoid any residual overvoltage.
-
Removal of the electronic board and visual inspection of the soldering.
-
Installing the new card and methodically reconnecting the connectors.
-
Soft start test — first in ventilation mode, then in air conditioning.
-
Check airflow, condensate drain and noise level.
The system restarted without error. The indicator lights stabilized, and the internal temperature quickly dropped, confirming a return to nominal performance.
Why these cards fail
In residential environments, Fujitsu wall unit electronic boards are often used by:
-
Voltage variations due to powerful equipment on the same circuit.
-
Moisture infiltration if the drain or box is not perfectly insulated.
-
Aging of internal capacitors , particularly after 7 to 10 years of use.
That's why we always recommend homeowners install a surge protector and have the unit checked before each air conditioning season.
Final result and customer satisfaction
After the repair, the Fujitsu air conditioner returned to quiet and stable operation. The customer, who was worried about having to replace the entire unit, was relieved to learn that a simple, targeted intervention was enough to bring his system back to life.
We also cleaned the interior coils and carefully replaced the cover, while explaining to the customer the correct preventive maintenance practices to adopt:
-
Clean the filter every two months.
-
Check the drain at the beginning of each summer.
-
Monitoring of any electrical fluctuations.
AirGreen expertise in Montreal
Every AirGreen intervention is based on a rigorous approach: precise diagnosis, cost transparency and lasting repair . Whether it is for a defective electronic card, a refrigerant leak or a blocked compressor , our RBQ and CCQ certified technicians provide professional service in all areas of Montreal, Laval, Longueuil, the North Shore and the South Shore .
In this specific case, the Fujitsu unit was refurbished without a complete replacement, demonstrating the importance of specialized HVAC expertise .