Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Remove the electrode assembly

Observation:

Thoroughly check the white spark electrodes for cracks and damage to the electrode ceramics and good general condition.
Check for correct spark gap. Gap should be 4.5mm +/- 0.5mm between the white electrodes.
Refit assembly after test
Note:
Before reassembly check the integrity of all disturbed gaskets and seals and replace as necessary.