E18
Thermona
Internal Electronics / PCB Fault
Boiler shows E18, no operation, often after power surges or lightning.
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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
Damaged main PCB on Thermona boiler, Internal short circuit, Overvoltage or surge damage, Corrupted firmware (on advanced models)
How to Fix / Troubleshooting
Safety: Isolate power before opening the boiler. Electronic repairs should be done by qualified personnel.
- Power cycle: Turn off the boiler at the isolator for several minutes, then restore power. If E18 reappears immediately, the PCB is likely faulty.
- Check supply voltage: Verify that the mains voltage is within the specified range and that polarity and earthing are correct.
- Inspect PCB: Look for obvious burn marks, swollen capacitors, or water damage on the Thermona PCB.
- Replace PCB (engineer level): A Thermona technician should replace the PCB with the correct part number and transfer any configuration links or EEPROM modules as required, then commission the boiler.
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Repair Difficulty
Professional Required
5/5
Required Part
Main Control PCB
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