An electronic card problem on a residential wall system
At AirGreen , we were recently called for an HVAC repair service in the Côte-des-Neiges–Notre-Dame-de-Grâce neighborhood of Montreal . The customer contacted us after noticing that their Midea wall-mounted air conditioner was no longer responding to the remote control and was not displaying any indicator lights, despite confirmed power.
Our team quickly diagnosed a faulty circuit board —a common problem on some wall-mounted air conditioner models exposed to voltage fluctuations or excessive humidity.
Initial inspection: power supply correct, but system inert
Upon our arrival, we carried out a series of tests:
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Checking the supply voltage at the main terminal: stable at 240 V;
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Continuity test on the connections between the indoor terminal and the outdoor compressor;
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Visual inspection of the control board , located on the right side of the unit, where slight oxidation was visible on the main relay connectors.
This oxidation, probably due to excessive condensation caused by irregular maintenance, had caused a minor short circuit that prevented the air conditioner from starting.
Intervention: replacement of the electronic card and internal cleaning
After confirming the diagnosis, we replaced the main circuit board with a genuine Midea part. Before reinstallation, our technician carefully:
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Cleaned and dried the card slot ;
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Checked the resistance of the evaporator sensor ;
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Cleaned the heat exchanger fins and air ducts;
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Tighten all electrical connections with dielectric compound to prevent future oxidation.
We also applied a UL94V-0 compliant protective coating to the new board to extend its durability against humidity—a precaution we consistently recommend in Montreal residential environments with high thermal variation.
Restart and Calibrate: Return to Full Efficiency
Once the new board was installed, the system rebooted without delay. The LEDs lit up, confirming proper communication between the indoor unit and the outdoor compressor.
We then carried out:
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A full cycle test (cooling and dehumidification);
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A check of the air flow at the fin outlet;
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A temperature control at the outlet, recording a difference of 11°C, proof of optimal performance.
The customer was able to observe smooth and quiet operation , with uniform air diffusion in the room.
Prevention and maintenance advice
We reminded the customer of some essential tips to preserve his system:
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Clean air filters at least once every 4 to 6 weeks during the summer;
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Avoid abruptly switching off the power supply after use, to allow the card to discharge properly;
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Schedule an annual professional maintenance , including checking the condensate drain and temperature sensors;
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Install, if possible, a dedicated surge protector to protect the card from network voltage spikes.
These simple measures ensure increased longevity and significantly reduce the risk of electronic failure.
AirGreen: HVAC expertise and guaranteed service in Montreal and surrounding areas
At AirGreen , we don't just repair—we analyze, explain, and optimize each system to ensure lasting comfort. Our technicians operate throughout Greater Montreal, Laval, Longueuil, the North Shore, and the South Shore , and are trained to repair all major brands: Midea, Fujitsu, Gree, Sharp, Zephyr, Bosch, Goodman, and more.
Each intervention is documented, tested and guaranteed. Our customers thus benefit from transparent monitoring , rapid service , and execution in accordance with Quebec HVAC standards .
Result: a Midea air conditioner ready for the summer season
Thanks to a precise and preventive intervention, this Midea wall unit has regained its full performance and energy efficiency. The customer, delighted with the speed of the service, has already scheduled his next annual maintenance with AirGreen.
It is this rigor, this expertise and this proximity that make AirGreen the trusted partner of Montreal households for all their HVAC repair and maintenance needs.