Boiler locks out with E18; may indicate gas valve or gas train fault.
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.
Possible Causes
How to Fix / Troubleshooting
Safety: Gas components must be serviced only by licensed gas technicians. Do not attempt to open or adjust the gas valve yourself.
- Visual inspection: With power off, inspect the gas valve wiring harness for loose plugs, damaged insulation, or signs of overheating.
- Connector check: Ensure the gas valve connector is fully seated and locked.
- Reset: Restore power and clear the error once. If E18 returns, stop resetting.
A licensed technician must test the gas valve coil resistance, verify correct voltage from the control board, and replace the gas valve or board as required.