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Réparation d’une thermopompe murale Mitsubishi à Lachine
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Repair of a Mitsubishi wall-mounted heat pump in Lachine

A blower failure occurred in the middle of the summer heat

At AirGreen , we often receive urgent calls in early summer when wall-mounted heat pumps stop blowing cold air. This is exactly what happened in a modern residence in Lachine , where a customer reported that their Mitsubishi Electric unit was no longer producing any airflow, despite the operating indicator light being on.

Initial diagnosis: the system turns on, but no longer blows

Upon arriving on site, our technician noticed that the Mitsubishi wall-mounted heat pump , installed in a central corridor serving several rooms, was displaying a green indicator light but no airflow was coming out of the shutters. However, the wall-mounted thermostat was indicating a temperature set at 21°C.

Our initial checks have confirmed that:

  • The outdoor compressor started normally;

  • The indoor unit was receiving the expected electrical voltage ;

  • No error codes were visible on the status light.

So we continued the diagnosis at the fan control module level.

The origin of the problem: a faulty control board

After opening the front panel, we tested the voltage on the DC Inverter blower motor . Result: no voltage was reaching the motor. The problem was therefore the indoor unit's control circuit board , which was no longer transmitting the power signal.

The most likely causes in this case:

  • Electrical surge or fluctuation on the network,

  • Excessive condensation having damaged components,

  • Aging of the electronic module (the device was more than 10 years old).

Repair carried out

We offered the customer an immediate replacement of the electronic card, a part available in our AirGreen Montreal service inventory.
The repair steps were as follows:

  1. Safe disconnection of the power supply ,

  2. Disassembly of the front panel and extraction of the defective card ,

  3. Complete cleaning of the internal compartment ,

  4. Installation of the new card and calibration ,

  5. Restart and full functional test .

Results after intervention

The system has resumed normal operation:

  • Air blown at 8°C ,

  • Smooth and silent ventilation ,

  • No voltage anomalies detected.

The customer immediately felt the difference: thermal comfort in the corridor and adjoining rooms was restored in less than 15 minutes.

Maintenance advice given to the customer

We took advantage of the intervention to remind you of some simple rules for maintaining a Mitsubishi wall-mounted heat pump :

  • Clean the filters every 3 to 4 weeks,

  • Avoid frequently turning the device off and on again at short intervals,

  • Protect the circuit with a dedicated circuit breaker or surge protector,

  • Have the refrigerant pressure checked at least once a year.

These best practices help prevent electronic failures like the one that occurred here and optimize the system's lifespan.

The AirGreen commitment: expertise, reliability and transparency

At AirGreen , we work daily on residential and commercial HVAC systems in Montreal, Laval, Longueuil, the North Shore and the South Shore . Our RBQ and CCQ certified technicians provide fast, methodical service that complies with the latest industry standards.

No matter the brand — Mitsubishi, Gree, Daikin, Fujitsu, Midea, Sharp or Bosch — we put our expertise at your service to diagnose accurately, repair sustainably and restore your comfort .

Is your wall-mounted heat pump no longer blowing?
Contact AirGreen , your trusted HVAC partner in Lachine and throughout Greater Montreal, for a quick diagnosis and reliable repair.