A heat pump breaks down just before a heat wave
As a week of high temperatures approached, a customer in Saint-Constant , on the South Shore , contacted us urgently: his Midea wall-mounted heat pump had just stopped blowing cold air. The indoor unit was working, the shutters were moving normally, but the outgoing air remained lukewarm, even in maximum cooling mode.
At AirGreen , we know that such a problem can stem from a variety of causes—from a lack of refrigerant to a compressor failure—and that prompt intervention is essential to prevent the situation from escalating.
Step One: Inspection and Visual Verification
Upon arrival, we inspected the indoor unit, visible in the photo: a properly installed Midea wall-mounted heat pump , with the filters accessible and securely in place . The top cover had been opened by the customer in the hope of restarting the system, without success.
Our technicians immediately proceeded to:
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A check of the filters : although partially clean, they had a fine accumulation of dust blocking the airflow.
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An observation of the evaporator coil : presence of slight frost at the base , a potential sign of underpressure in the refrigeration circuit.
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Careful listening to the fan and outdoor compressor via the communication line — no audible start of the compressor.
These clues pointed our diagnosis towards a failure of the communication module or a refrigerant leak .
Step 2: Electrical diagnosis and communication test
Using our Midea diagnostic equipment, we measured the voltage between terminals 1-2-3. The communication was intermittent: the indoor unit board was sending the signal, but no response was received from the outdoor compressor .
We also noticed a flashing error code on the display , corresponding to a main board failure of the outdoor unit.
To confirm, we temporarily plugged an AirGreen test unit into the same power grid: the signal worked perfectly.
The problem therefore came from the electronic card of the Midea compressor , faulty due to a power surge that occurred during a recent storm.
Step 3: Replacing the electronic card and reconfiguring
After explaining the situation to the customer, we ordered the Midea MSAG-12HRN1 series control card , which is compatible with his installation.
A few days later we came back for:
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Unplug the system and isolate the communication line.
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Replace the outer PCB board.
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Reconfigure the compressor frequency and initialization parameters.
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Perform a full commissioning test .
Upon restart, the compressor activated normally and the indoor unit started blowing air at 10°C , confirming that the refrigeration circuit and temperature sensors were functional.
Step 4: Cleaning and Preventive Maintenance
Before concluding our intervention, we have:
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Cleaned the interior filters and evaporator coil using AirGreen biodegradable product.
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Checked the condensate drain to avoid any risk of overflow.
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Tested the fan speed on all levels.
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Customer advised to schedule annual maintenance to prevent dust buildup and avoid electrical overloads during peak periods.
Result: restored comfort and optimal performance
After the intervention, the system worked perfectly. The customer immediately noticed:
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A stable room temperature .
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More powerful airflow .
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Reduced operating noise through thorough cleaning.
We also added surge protection to the power line, to prevent a future storm from damaging the circuit board again.
Why use AirGreen for your HVAC repairs?
This intervention perfectly illustrates the value of a rigorous and methodical diagnosis . At AirGreen , we combine:
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In- depth expertise in recognized brands such as Midea, Sharp, Fujitsu, Gree, Zephyr and Lennox .
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Advanced diagnostic tools to identify faults invisible to the naked eye.
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Fast and professional service , covering the entire Greater Montreal area, from Montreal to Laval , including Longueuil, the North Shore and the South Shore .
Each repair is carried out with care, in compliance with safety standards and manufacturer recommendations.
Our priority: guaranteeing performance, durability and peace of mind to each of our customers.
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