Worcester 28i hot water intermittent fault

[mark o'neill]

The Ch and hot water work fine for a few weeks, but then the hot water will stop working, with the hot water tap running if you tap the boiler very gently the boiler will burst into life and the hot water works. This will happen a few times then no problems for a week or so and then same fault.
I changed the flow turbine and no fault for a month, but same fault back again now.
Any ideas.?

 

[ollski]

Pcbs are notoriously flakey on the 28i

 

[mark o'neill]

Thanks for fast reply. Any idea how big a job a PCB change is.