How to Replace Ignition Electrodes on Bosch Water Heaters

How to replace ignition electrodes on Bosch water heaters since there is no spark and the error code EC or EA is shown? What is the problem and how to fix the heater?

There are two error codes that are related to the ignition and flame rod problems: EC - ionization failure during operation and EA - no flame ionization detected with water flow. In order to fix the problem, components have to be cleaned or in worst case replaced.

Tools: Phillips screwdriver, small adjustable wrench and the fine steel wool for cleaning the electrodes.

ignition electrodes and flame rod on bosch tankless water heater


  • Unplug the water heater and turn off the gas supply on the manual shut off valve.

  • Remove the front cover by taking off the two screws, which are located in the lower and rear part of the unit.

  • Locate two upper and two bottom clips that are holding the combustion chamber cover, and unclip them.

  • Once the cover has been removed, locate the ignition electrodes located in the middle of the combustion chamber.

  • Disconnect two yellow wires and one small flame sensor wire.

  • Take off two nuts from the ignition assembly.

  • Now, remove the ignition electrodes, flame rod, and gasket from the unit. The flame sensor rod is located on the left.

  • Check out the gasket for damages and color changes. If it is needed replace it with the new one.

  • Use the steel wool to clean the flame rod and ignition electrodes from any residues.

  • Put the gasket on one stud.
  • Either you are installing the cleaned electrodes or replacing, do it carefully.

  • Make sure that there is a correct seal between the heat exchanger and ignition group. This is very important.

  • Tighten the two 8-mm nuts.

  • Reconnect the wires.

  • Put the combustion chamber cover and the front cover back.

  • Turn on the manual shut off valve and resume the power.

If interested in more details, check it out here.

(photo credit to Bosch)

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