E18
Chaffoteaux Flame Ionization / Grounding Fault

Furnace displays E18, may be related to ionization current or grounding.

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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

Poor earth connection, Contaminated flame electrode, Incorrect polarity of mains supply, Faulty control board ionization circuit

How to Fix / Troubleshooting

Safety: Isolate power and gas before accessing the burner compartment.

  • Check mains polarity and earth: Have a qualified electrician verify that live, neutral, and earth are correctly connected and that earth resistance is within limits.
  • Clean flame electrode: Remove the flame sensing electrode and clean the tip with fine emery cloth. Ensure it is correctly positioned in the flame path when refitted.
  • Inspect wiring: Check the ionization lead from the electrode to the control board for damage or loose connections.
  • Reset: Restore power and reset the furnace. If E18 persists, the control board may require replacement by a professional.
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Repair Difficulty

Hard 4/5

Required Part

Flame Detection Electrode
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