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 gas supply to property and the inlet on the gas valve.
Has the gas supply pipework been purged?
Check for low pressure when the gas valve opens.
Gas valve failing to open: check for voltage to the valve and for possible blockage on inlet filter of the gas valve.
Check spark is present,.
If there Is no spark, check the plug connection or replace the faulty ignition transformer.
Obstruction in the air intake to the fan leading to incorrect O2 levels. Check if non-return valve (bearing plate) is damaged or stuck.
Check the spark electrode or the lead failure.
Check the flame sense or the lead failure.
Check the rectification ground (black wire to heat exchanger).
Check the burner for damage.
Heat exchanger is blocked or restricted.
Condensate trap is blocked or restricted. Condensate pipe is frozen.
Flue is blocked or restricted.