H23
Panasonic Ambient / Internal Temperature Sensor Error

Panasonic water heater shows H23; unit may not start or may shut down with sensor‑related issues.

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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

Faulty internal thermistor, Loose sensor connector on PCB, Damaged wiring, Defective PCB sensor input

How to Fix / Troubleshooting

Safety: Disconnect power before opening the unit.

  • 1. Power reset: Turn OFF power for several minutes, then restore and test.
  • 2. Locate internal sensor (qualified persons):
    • Remove the front cover.
    • Identify the small thermistor used for internal or ambient temperature monitoring on the PCB or chassis.
  • 3. Inspect wiring and connector:
    • Ensure the sensor connector is firmly seated and wires are intact.
  • 4. Replace sensor: If wiring is good but H23 persists, replace the internal temperature sensor with a Panasonic‑specified part.
  • 5. If still unresolved: The PCB may be faulty and should be replaced by an authorized technician.
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Repair Difficulty

Medium 3/5

Required Part

Internal Temperature Sensor
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