No hot water from worcester 24cdi Combi

[archerybrian]

My boiler has started to play up with the hot water. The heating works fine but the hot water will run cold after a short while. The HW demand light is not on.
I tried turning the heating off and then turned on the tap. The light came on and the burner ingnited for about 15 secs then went out and the light went off. Checking the book it could be the control board, microswitch or water diverting valve. As the it runs for a short while I feel it might be the valve. Can anyone confirm my suspisions.
Brian

[gasman]

I doubt that the PCB is at fault and i would go for the diverting valve to be the problem especialy if it has not been serviced and had its daiphragm changed witnin the last couple of years.

[archerybrian]

Thanks gasman

I have been doing some more investigating and the plunger on the valve moves out when the tap is turned on and makes the microswitch and the hw demand light comes on and the burner fires but goes out (Light and Flame) after about 15 secs. If i push the microswitch with a screwdriver it works. The plunger comes out but doesn't go fully back when the light goes out. I think it could probably be a damaged diaphram.