Hi, got a Vaillant 242e and its not igniting for either hot water or heating. It makes all the right clicking sounds, pump starts and flue fan starts (only when running hot water tho?).

I've replaced the Flame Ignition PCB and Fan Module PCB tonight, and the mainboard was replaced 2 years ago. However its still not igniting.
My brother in law is a plumber and we've gone thru the fault diagnosis in the Vaillant manual, all of which lead to it being one of the PCB's.

Could it be the Thermostat PCB that is at fault or might it be something else?

Also worth mentioning, I can't see a pilot light in it, however the reset switch hasnt popped out??

Full Model No. :- VCW GB 242E