Display shows 'Er3' and thermostat cannot store new schedules or settings.

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.

Possible Causes

EEPROM/flash wear-out, Memory write failure, Corrupted configuration sector, Power loss during write operation

Safety: No mains work is required.

Factory reset: Perform a full factory reset to clear corrupted data. Re-enter schedules and preferences.
Avoid rapid changes: After programming, avoid rapidly changing settings to reduce write cycles.
Stable power: Ensure batteries are fresh or mains supply is stable to prevent power loss during writes.
Replace thermostat: If Er3 persists and settings are not retained, the memory chip is defective. Replace the thermostat.

Medium 3/5

Non-Volatile Memory (EEPROM/Flash) on PCB

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