E12
Delta Dore Non-Volatile Memory (NVM) Error

E12 displayed and thermostat cannot read or write schedules; programming changes are not saved.

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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

Corrupted EEPROM/flash memory, Power loss during firmware update, Main PCB fault, Excessive electrical noise on supply

How to Fix / Troubleshooting

Safety first: For mains-powered units, isolate power before opening the housing.

  • Soft reset: Perform a soft reset via the menu: Menu > Settings > Reset. Re-enter a simple schedule and test if it is retained after a power cycle.
  • Factory reset: If soft reset fails, perform a full factory reset (consult the Delta Dore manual for your model). Reconfigure the thermostat from scratch.
  • Stabilize power: If the thermostat is on a circuit with frequent brownouts or interference (e.g. shared with large motors), consider moving it to a more stable circuit or adding surge protection.

If E12 continues and schedules are not saved, the internal memory chip is defective. Replacement of the thermostat or main PCB is required.

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Repair Difficulty

Hard 4/5

Required Part

Delta Dore Thermostat Main PCB (Memory Circuit)
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