H27
Panasonic Internal PCB Communication Error

Panasonic water heater shows H27; may be related to internal communication between PCBs on multi‑board models.

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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

Loose inter‑board connector, Damaged communication cable, Faulty sub‑PCB, Defective main PCB

How to Fix / Troubleshooting

Electrical safety: Disconnect power before accessing internal PCBs.

  • 1. Power reset: Turn OFF power for 10 minutes, then restore and test.
  • 2. Inspect inter‑board connections (qualified persons):
    • Remove the front cover.
    • Locate ribbon cables or harnesses between the main PCB and any sub‑PCBs.
    • Reseat connectors firmly.
  • 3. Check for corrosion or moisture:
    • If there are signs of water ingress, locate and repair the leak source before replacing electronics.
  • 4. If H27 persists: One of the PCBs is likely defective and should be replaced by an authorized Panasonic technician.
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Repair Difficulty

Hard 4/5

Required Part

Sub‑PCB Assembly
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