Ideal Isar HE35 CH-HW changeover problem

[Leighfire]

Hi I have a problem with my Boiler. Ideal Isar HE35

Fault:-
boiler operates fine providing hot water on demand.
I tested the heating yesterday, all worked fine until I called for hot water, it would not change over and provide hot water, I then cancelled the CH but the boiler would not change over, I finally reset the boiler and reverted back to original position, ie providing hot water on demand fine.

I tried the same process, enable CH, call for HW and same happens.

Any ideas or thoughts please?

Thank you

 

[Leighfire]

Any thoughts please?

 

[Leighfire]

New PCB fitted, still not right.
Before i spend for a new diverter valve any help please?

 

[gigz]

Yeah get a boiler engineer. Not being funny but why go straight for the pcb ? If your'e going to guess at least go cheapest first.