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Appel de service pour une thermopompe murale Fujitsu à Outremont
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Service call for a Fujitsu wall-mounted heat pump in Outremont

Diagnosing an Intermittent Fault on a Residential Wall Unit

Recently, our AirGreen team was called in for an HVAC service call in Outremont , a typical residential neighborhood in Montreal. The customer contacted us after noticing that their Fujitsu wall-mounted heat pump was intermittently no longer producing cold air, despite a normal display on the remote control. This situation is typical of an internal electronic problem or a blockage in the condensate drain .

Initial inspection: a subtle, but recurring failure

Upon arrival, we performed a complete diagnostic on the wall unit, a Fujitsu Halcyon series model of approximately 12,000 BTUs, installed in an open-plan living room. The unit, well maintained by the owner, however, showed some signs of internal overheating after several cycles.

Initial findings:

  • The unit powered on properly.

  • The outdoor compressor started normally.

  • After 10-15 minutes the indoor unit would shut down on its own with no error code displayed.

  • A slight clicking noise came from the electronic panel upon restart.

These observations pointed us towards a fault related to the control board or a faulty temperature sensor .

In-depth diagnosis: faulty control board

We first checked the air filters , fan motor , and condensate drain – all in good condition. Then, using our multimeter and thermistor tester , we tested the evaporator and return air temperature sensors.

The results showed an inconsistent reading from the air outlet thermistor , a critical component in regulating the cooling cycle. However, the intermittent failure suggested a fault on the main control board (PCB) , which is responsible for processing this data.

After consulting the Fujitsu technical database, the diagnosis was confirmed: defective PCB board .

Intervention: replacement of the electronic card

We have undertaken the following steps:

  1. Power supply cut-off to ensure the safety of the intervention.

  2. Removing the front cover and control panel from the wall unit.

  3. Replacement of the PCB board with an original Fujitsu part, compatible with the serial number of the device.

  4. Careful reconnection of sensor cables, fan and electronic expansion valve.

  5. Complete system calibration and functional test in air conditioning and heating mode.

After restarting, the heat pump operated stably for more than 40 minutes without interruption or error, confirming the success of the repair .

Result: performance and reliability restored

Thanks to this intervention, the Fujitsu unit regained its original efficiency and quiet operation . The customer, who often used the heat pump in supplemental heating mode in the winter, noticed better temperature control and increased cycle stability .

Our team also took the time to explain to the client some good preventive maintenance practices , including:

  • Clean air filters monthly.

  • Avoid blocking air circulation around the indoor unit.

  • Have the system inspected once a year before the hot season.

AirGreen expertise in Outremont and throughout Montreal

At AirGreen , we put our expertise at the service of homes and businesses in Montreal, Laval, Longueuil, the North Shore and the South Shore . Our qualified technicians work on all major brands, including Fujitsu, Midea, Gree, Lennox, Zephyr, Sharp and Bosch .

Each intervention aims not only to repair the breakdown , but also to improve the reliability and energy performance of your HVAC system.

Is your Fujitsu wall-mounted heat pump experiencing frequent shutdowns or irregular cycles?
Call AirGreen , your trusted HVAC specialist in Montreal, for a professional diagnosis and lasting repair.