Have the above boiler that's making all the right noises but fails to ignite.
You can hear a faint ticking from control board like ignition spark but no spark appears in the window of boiler.
The boiler has been taking longer to ignite of late.
If you let the control board swing down with it's cover removed you can see a spark visible on component SG1 not sure if this is what you should see or not.
Any suggestions welcome
Thank you

David, September 2014

http://www.keeptheheaton.com/acatalog/Potterton_Spark_Generators.html

Mavis, September 2014

SG1 will be a spark generator
It sends a high voltage pulse to jump an air gap - the spark lighting the pilot flame - if the high voltage finds an easier route it will run to earth the easy way and the pilot flame will not light.

Make your test with the lights out or with a coat over your head - see exactly where the spark is going - try to make it work correctly - it may be that the spark is being attracted by some conductive dirt.

Otherwise replace the circuit board yourself or have a professional do it.

Good luck...

PL Travers (Mrs), September 2014