H4
Fujitsu
Indoor PCB Overheat or Power Supply Error
Indoor unit shows H4, unit may stop unexpectedly
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Blocked indoor unit ventilation around PCB, High ambient temperature in installation location, Failing indoor PCB power supply components, Loose connections causing arcing and heat
How to Fix / Troubleshooting
Safety first: Turn off power at the breaker before removing covers. Electronic components can remain hot after shutdown.
- Check installation: Ensure the indoor unit has adequate clearance from the ceiling and walls for ventilation as per Fujitsu installation manual.
- Clean dust: Carefully vacuum dust from around the PCB and power supply area without touching components.
- Inspect connectors: Look for discolored or melted connectors on the indoor PCB. Reseat them if they appear loose.
- Technician repair: If H4 persists, the indoor PCB power supply may be failing and should be replaced by a professional.
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Repair Difficulty
Hard
4/5
Required Part
Indoor Main PCB
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