A quiet heat pump… too quiet
At AirGreen , we often receive calls from customers surprised by the complete silence of their wall-mounted system. This was precisely the case during this service call in Longueuil , where a customer contacted us because their Midea wall-mounted heat pump seemed to be completely unresponsive—no noise, no display, and no airflow.
On site, our technician confirmed the symptom: no sign of life from the indoor unit. The remote control worked, but the heat pump remained inert, with no LED flashing or response to the infrared signal. This type of failure, often linked to the power supply or the control board, required a complete and methodical diagnosis .
Step 1: Checking the power supply and protections
The first step was to check the power supply voltage at the wall unit's input. Using a multimeter, we measured a stable voltage of 240 V , confirming that current was reaching the indoor unit. However, no current was flowing to the main circuit board.
A quick inspection revealed a blown internal fuse , likely due to a voltage spike that occurred after a power outage . This type of surge is quite common in residential areas on the South Shore, especially during periods of mass network restarts.
Step 2: Inspection of the electronic board
We then removed the front cover and removed the control board. The signs of heating around the fuse confirmed our hypothesis. As a precaution, we also checked:
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Continuity of the low voltage transformer ,
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The state of the main capacitor ,
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The connectors connecting the board to the display module and the fan motor.
Result: only the input protection section was defective , the rest of the circuit was intact.
Step 3: System Repair and Calibration
At AirGreen , we always favor targeted repairs over complete appliance replacement when possible and safe. In this case, we replaced the thermal fuse and the ignition resistor , then applied a dielectric insulating varnish to the repaired welds to prevent future electrical arcing.
Once the board was reassembled and the system reconnected, we powered the unit back up. The power indicator light instantly lit up, a sign that the Midea heat pump was coming back to life.
Step 4: Functional Tests
To validate the repair, we ran a full heating cycle. In less than two minutes, the hot airflow reached 36°C at the outlet, and the outdoor compressor started normally. No abnormal noise was detected, and the automatic defrost cycle began after 25 minutes, proving that the system was once again responding to all its internal commands.
We finished with a communication test between the indoor unit and the outdoor module , essential on Midea models with inverter technology. The control PWM signals were stable, confirming the complete success of the repair.
Step 5: Prevention Tips
Before leaving the premises, our technicians advised the client to install a dedicated surge protector for their heat pump. This often-overlooked accessory prevents most circuit board failures caused by voltage fluctuations. We also reminded them of best practices:
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Avoid unplugging the heat pump frequently ,
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Clean the filters monthly ,
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Schedule an annual professional maintenance before each heating season.
Result: restored comfort and secure system
Thanks to a quick and meticulous intervention , the Midea wall-mounted heat pump was restored to optimal operation. The customer was able to enjoy its comfort without having to replace the entire unit, a considerable saving.
At AirGreen , we provide precise and durable repairs for all types of HVAC systems in Montreal, Laval, Longueuil, on the North Shore and the South Shore , with an approach focused on reliability and customer satisfaction.