Sudden breakdown in a renovated bathroom
A homeowner in Saint-Léonard , Montreal, recently contacted us after noticing that his Sharp wall-mounted heat pump had suddenly stopped blowing hot air. The unit, installed high up in a recently renovated bathroom , was exhibiting behavior typical of a faulty circuit board or sensor : the indicator light would come on, the damper would open, but no airflow would come out.
In this type of environment, where humidity is naturally high, wall-mounted devices must be perfectly sealed and well maintained . It is often in humid rooms that the first signs of failure appear—internal condensation, sensitive sensors, or corrosion of connectors.
Diagnosis: Internal communication failure
Upon arrival, we undertook a complete diagnostic of the Sharp wall-mounted heat pump , model ZU1 range , a series popular for its quiet performance and compact design. After unplugging the unit and removing the front cover, our technicians observed:
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No obstructions in the filter or in the evaporator , proof of regular maintenance.
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Flashing red light in code E5 , indicating loss of communication between the main board and the fan motor .
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Slight traces of moisture on the internal temperature sensor connector .
We then checked the voltages on the electronic board: the values were stable at 230V AC, but the DC control signal to the motor was not responding. The diagnosis was clear: the main control board was damaged .
Intervention: card replacement and complete calibration
1. Safe disconnection and disassembly
Before any intervention, we cut off the power supply at the wall source. The unit was partially disassembled to access the main PCB , located on the right under the front panel.
2. Installing the new card
We replaced the defective board with an original Sharp model , compatible with the ZU1 and ZU2 series. Before assembly, we applied a protective dielectric coating to the connectors to prevent moisture from reappearing.
3. Calibration and functional test
After reinstallation, we performed a full system reset . Final measurements showed:
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Blown air temperature: 42°C in heating mode.
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Noise level reduced to 23 dB.
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Smooth and stable restart cycle.
The device has regained its full performance, with perfectly silent operation and uniform air diffusion throughout the room.
Prevention: Protect your heat pump in a humid environment
In bathrooms, kitchens or laundry rooms, we always recommend adopting a few simple reflexes:
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Install an effective moisture extractor to reduce condensation.
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Clean the heat pump filters every 4 to 6 weeks .
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Avoid directing the airflow directly towards the shower or sources of humidity .
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Schedule an annual professional maintenance including an inspection of the electrical connections and the control board.
These precautions extend the life of the unit and greatly reduce the risk of corrosion or electronic failure.
AirGreen expertise in Saint-Léonard and throughout Montreal
At AirGreen , we work weekly on Sharp, Fujitsu, Gree, Midea and Bosch wall-mounted heat pumps throughout the Greater Montreal area. Our RBQ and CCQ certified technicians are fully proficient in repairing electronic boards, temperature sensors, motors and defrost probes .
Our approach is always based on transparency:
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Clear diagnosis before any repair.
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Exclusive use of original parts .
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Written guarantee on each intervention.
Thanks to this rigor, we were able to give this Saint-Léonard customer immediate thermal comfort , without costly replacement.
Caution: Working on heat pump circuit boards and motors requires advanced technical expertise and calibrated tools. Never attempt to disassemble or short-circuit a wall-mounted unit yourself. Call a certified professional.