Remedy
Tip: Check the ceramic insulator is not damaged, this can cause the spark to earth, twist and pull the ceramic insulator to ensure it is not broken.
Check the flame sense and the lead and replace if required.
Check electrode assembly for damage and replace if required.
Check the earth tags on the appliance and on the electrodes.
Check the operation of the condensate trap and that no water is collecting in the sump.
Replace the electrode assembly.
Replace the gas valve.
Replace the control unit.