H10
Panasonic Mixing / Outlet Temperature Control Error

Panasonic water heater shows H10; unit may start but then shut down with unstable temperature.

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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 outlet thermistor, Sticking modulating gas valve, Scale in heat exchanger affecting heat transfer, Defective control PCB temperature regulation

How to Fix / Troubleshooting

Safety: Risk of scalding if temperature control is faulty. Test water temperature carefully.

  • 1. Confirm set temperature: Ensure the set temperature on the controller is reasonable (e.g., 40–50°C) and not at maximum.
  • 2. Check flow rate:
    • Very low flow can cause unstable temperature. Open the tap more fully.
    • Clean aerators and shower heads.
  • 3. Inspect outlet thermistor:
    • Follow steps similar to H07 to check wiring and condition of the outlet temperature sensor.
    • Replace if damaged.
  • 4. Descale heat exchanger: If the unit is older or in a hard‑water area, perform a descaling procedure to restore proper heat transfer.
  • 5. If H10 continues: The modulating gas valve or PCB control algorithm may be faulty. Have an authorized Panasonic technician test and replace components as needed.
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Repair Difficulty

Hard 4/5

Required Part

Outlet Water Temperature Sensor (Thermistor)
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