Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove ignition / rectification electrode
(remove 2 black plugs on top of boiler casing, this will allow access to undo bolts with 3mm Allen key & pull electrode up and bend around heat exchanger)

Measurement:

Check electrode is in good overall condition:
  • Ceramic not cracked
  • Electrode not warped or distorted
    Measure the resistance across the electrode (if needed clean tip of electrode to get a good connection).

    Resistance should be short circuit (zero resistance).