Halstead ace high combi - no independent hot water

[jayvee]

I have a Halstead Ace High Combi boiler, the central heating is fine but the burner for the hot water does not always fire, when it does fire it does not always remain on.
The central heating has to be on or it doesn't work at all.
The bathroom basin hot tap is always ok if the tap is turned fully on first.
The shower (mixer tap) is intermittent.
The kitchen tap does not ignite the burner even if fully on ?????
Any ideas please?
Thankyou.

 

[chrishutt]

Diaphragm failure in diverter valve (assuming this boiler has a Giannoni diverter). Do a search for more details.