Set Appliance State:

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

Observation:

Thoroughly check all three electrodes for cracks and damage to the electrode ceramics and good general condition.
Confirm correct spark gap between the white spark electrodes of 4.5 mm (+/- 0.5 mm), adjust as required.
Note:
This component requires the air/gas manifold and fan assembly to be removed therefore the gasket between the gas air manifold and the heat exchanger must be changed.