Repair of a Midea wall-mounted heat pump in Sainte-Dorothée

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:

• Stable supply voltage at the input terminal: 240 V confirmed.

• Communication between indoor and outdoor unit: absent.

• Fuses and thermistors tested: in good condition.

• 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:

1. Safe disconnection of the unit and discharge of the capacitors.

2. Removing the power module , including terminal blocks and connectors.

3. Reassembly of the new PCB respecting the Midea color wiring codes.

4. Continuity and insulation test before re-energizing.

5. 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 :

• Discharge pressure: Meets Midea specifications.

• Power consumption: stable.

• 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:

• Installing a surge protector dedicated to your HVAC system.

• Annual cleaning of filters and coils to reduce electrical load.

• 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.