When a faulty electronic card paralyzes comfort
At AirGreen , we work weekly on residential HVAC systems that, after years of faithful service, are showing signs of electronic failure. This is precisely what happened during this service call in Sainte-Dorothée, Laval , where a Midea wall-mounted heat pump refused to start, displaying an intermittent error code on the indoor digital panel.
Diagnosis: Main board failure
Upon arrival, the customer reported that the unit had stopped blowing cold air for a few days. The wall display would turn on briefly, then turn off completely.
Our technicians carried out a series of checks:
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Stable supply voltage at the input terminal: 240 V confirmed.
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Communication between indoor and outdoor unit: absent.
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Fuses and thermistors tested: in good condition.
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Main PCB : traces of overheating visible on a relay module.
Upon opening the unit, we found that the power module showed blackening around a connector—a classic sign of a short circuit due to a faulty relay. The display board was also unstable, with some LED display segments partially off.
Solution: Replace the complete control module
After confirming the fault, we proceeded to completely replace the original Midea main board and display module , both supplied directly by our authorized parts network.
This replacement requires precise calibration:
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Safe disconnection of the unit and discharge of the capacitors.
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Removing the power module , including terminal blocks and connectors.
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Reassembly of the new PCB respecting the Midea color wiring codes.
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Continuity and insulation test before re-energizing.
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Reprogramming of factory settings (auto mode, vertical scanning, default temperature).
Result: comfort and reliability restored
Once the installation was complete, the system restarted normally. The compressor started after 3 minutes, and the heat pump immediately began blowing air at 18°C in cooling mode. We performed a complete performance test :
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Discharge pressure: Meets Midea specifications.
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Power consumption: stable.
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Internal/external communication: restored without error.
The relieved customer found optimal comfort in his living room—proof that a methodical diagnosis and professional intervention can often significantly extend the life of a heat pump.
AirGreen tips to avoid similar breakdowns
Heat pump circuit boards are sensitive to voltage fluctuations and humidity. To prevent future failures, we recommend:
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Installing a surge protector dedicated to your HVAC system.
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Annual cleaning of filters and coils to reduce electrical load.
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A preventive inspection every spring to check connections and relays.
Our certified technicians serve all of Laval, Montreal, Longueuil, the North Shore and the South Shore , and have a complete stock of original electronic parts for Midea, Fujitsu, Sharp, Zephyr, and many other brands .
Every repair is performed according to CSA safety standards and manufacturer guidelines, ensuring long-lasting performance and quiet operation.
At AirGreen, we know that a small component can make all the difference between a comfortable summer and a breakdown in the middle of a heatwave. That's why our teams respond quickly, accurately, and always with certified parts.