A service call in an open-plan residential office
At AirGreen , we respond to service calls every day in a wide variety of settings: single-family homes, condos, duplexes, and even home office spaces. Recently, our team traveled to Sainte-Julie , on the South Shore , to diagnose a Midea wall-mounted heat pump that was no longer blowing cold air into an open-plan office on the second floor of a house.
Symptoms observed: a device that operates without cooling
The customer, who is permanently working from home, contacted us after several days of intense heat. His Midea wall-mounted indoor unit was turning on normally, the operating lights were on, but the expelled air remained lukewarm, even at 18°C. Outside, the compressor appeared inactive , although the fan was running intermittently.
These clues pointed us towards a communication problem between the indoor unit and the condenser , or towards a malfunction of the control module .
Step 1: Complete diagnosis and communication test
Upon arrival, we performed a continuity test on the 4-wire cable connecting the two units. The result: fluctuating voltage and an erratic communication signal. Further analysis revealed that the control wire (data signal) had abnormal resistance.
The cable, installed for several years, showed signs of oxidation at the external terminals, probably due to humidity and salt accumulated during the winters.
Step 2: Replacing the communication cable
Our technician completely replaced the shielded 14/4 cable , in accordance with the Midea manufacturer's recommendations. Once the connection was reestablished and insulated in a rigid sheath, we restarted the system.
This intervention immediately restarted communication between the electronic boards. The compressor restarted, and fresh air began circulating in the room a few minutes later.
Step 3: Verification of parameters and calibration
To ensure proper operation, we performed the following steps:
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R410A refrigerant pressure control;
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measurement of the blowing temperature (dropped to 8.7°C after 15 minutes);
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checking power consumption to ensure the compressor was operating at full capacity;
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Recalibrating the room sensor using the Midea diagnostic tool.
The entire system was then tested on a complete cooling/heating cycle to validate the performance of both modes.
Step 4: Preventive maintenance and personalized advice
Taking advantage of the repair, our team carried out a preventive cleaning :
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dusting of the interior coil and washable filters;
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cleaning the tangential fan;
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disinfection of the condensate tray using a biodegradable antifungal product;
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drain check to prevent future overflow.
We also recommended that the client perform a complete annual maintenance before each summer , especially for facilities used daily as workspaces. This routine reduces the risk of breakdowns due to overheating and maintains the system's energy performance.
Results: Restored comfort and regained performance
Once the repair was completed, the office's ambient temperature dropped from 27°C to 22°C in less than 20 minutes.
The delighted customer was able to resume his professional activities in a comfortable and quiet environment. The Midea wall-mounted heat pump was once again operating at full efficiency, with stable power consumption and optimal performance.
AirGreen: HVAC expertise serving the South Shore
This intervention perfectly illustrates AirGreen 's philosophy: rigor, transparency, and efficiency. Our technicians are trained to quickly diagnose electrical, electronic, or mechanical problems on all major brands— Midea, Gree, Fujitsu, Sharp, Lennox, Friedrich, Bosch, Goodman , and more.
We operate on the South Shore, in Sainte-Julie, Saint-Bruno, Boucherville, La Prairie and Brossard , with a constant commitment: to offer durable repairs that comply with the standards of the Régie du bâtiment du Québec (RBQ) and the Commission de la construction du Québec (CCQ) .
Warning:
Work on HVAC systems should only be performed by certified technicians. Incorrect wiring or calibration can permanently damage the device's electronic board.