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Réparation d’une thermopompe murale Fujitsu à Pointe-Claire
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Repair of a Fujitsu wall-mounted heat pump in Pointe-Claire

Electronic fault on a power supply board: an accurate diagnosis and a successful repair

At AirGreen , our service interventions are not limited to mechanical breakdowns. Increasingly, we are called upon to diagnose and repair complex electronic failures , particularly on Fujitsu wall-mounted heat pump systems .
In this case, our team intervened in Pointe-Claire , in the west of Montreal, for a Fujitsu outdoor unit that refused to start despite a functional power supply.

Initial diagnosis: an inactive power card

The customer reported that the Fujitsu wall system was no longer responding to the remote control. No lights were illuminated, and no activity from the outdoor fan was detected.
After the first checks:

  • Input voltage measured at stable 240V;

  • Internal fuses intact;

  • But no output voltage to the compressor or control board.

These clues quickly pointed the diagnosis towards a faulty power electronic board (PCB) – a common problem on inverter technology models.

Step 1: Disassembly and inspection of the main board

After securing the power, our technician removed the front panel of the condenser to access the electronics compartment.
A careful visual inspection revealed:

  • Slight discoloration around one of the inductors ;

  • A smell of burnt component ;

  • And a MOSFET transistor showing signs of excessive heat.

The power supply board, responsible for converting AC to DC voltage for the compressor, had apparently suffered a power surge.

Step 2: Continuity Tests and Component Measurement

To confirm the diagnosis, we carried out:

  • A continuity test on the main tracks of the circuit;

  • Checking electrolytic capacitors with an ESR multimeter;

  • And a control of the power resistors .

The result: a burned-out primary inductor and a faulty control MOSFET . These components prevented the board from sending the start signal to the compressor.

Step 3: Component Replacement and Safe Reinstallation

We have replaced the complete power module , an original Fujitsu part, supplied directly by our authorized distribution network.
During reassembly, all low voltage connections were cleaned, and we added thermal insulation film under the new components to prevent future overheating.

Each cable was checked according to the manufacturer's wiring diagram , including:

  • CN1 connection: main power supply;

  • CN3 connection: communication with internal card;

  • CN9 connection: fan control;

  • CN12 connection: Inverter compressor signal.

Step 4: Power-on Test and Inverter Calibration

Once the board was replaced, we restored power and ran a soft-start test .
The compressor turned on silently again after 20 seconds, followed by the condenser fan.
The measurements showed:

  • Starting current: 2.4 A;

  • Low pressure: 110 psi;

  • High pressure: 245 psi;

  • Indoor blowing temperature: 12.8°C.

We then ran the Fujitsu automatic calibration procedure , which adjusts the compressor frequency according to the thermal load detected by the probes.

Step 5: Maintenance Tips and Surge Prevention

Electronic card failures can often be prevented with a few simple steps:

  • Install a surge protector dedicated to the heat pump circuit;

  • Avoid sudden power outages via the main circuit breaker;

  • Have the connections inspected at least once a year by a certified technician;

  • Maintain free ventilation around the outdoor unit to prevent heat buildup.

Results: restored performance and reassured customer

After the repair, the Fujitsu heat pump regained its full cooling and heating power . The customer was able to enjoy quiet operation , optimized power consumption and precise temperature control .

This type of repair perfectly illustrates the skill of our teams: working with precision on complex electronic systems , while guaranteeing safety, reliability and compliance with manufacturer standards .

In conclusion

This electronic board repair on a Fujitsu wall-mounted heat pump in Pointe-Claire demonstrates AirGreen 's expertise in HVAC electronic diagnostics .
We operate throughout Greater Montreal , in Laval, Longueuil, on the North Shore and the South Shore , to bring Fujitsu, Midea, Gree, Mitsubishi systems and several other leading brands back to life.

Every repair is an opportunity to extend the life of the equipment , avoid premature replacement and ensure lasting comfort for our customers.