Worcester Bosch 28cdi diverter valve

[rafal135]

Hi
I am replacing suspect diverter valve on old Worcester Bosch 28cdi. There is a small black slotted screw there (see the photo).
Could someone advise me what is it for, is it an adjustment?
Thank you very much
Rafal

 

[ShaunCorbs]

What’s the fault ?

 

[rafal135]

DHW not getting hot, the plate heat exchanger looks nice an shiny inside

What’s the fault ?

 

[rafal135]

I already replaced the diverter valve ( bought reconditioned) but the valve was leaking from that "black screw" so I put the old one back