the hot water only works when the central heating is put on,and the timer seems to do nothing,,the hot water sometimes works for about 10 mins then stops for no reason...

bri, September 2006

I have this problem on a ravenheat boiler - Just changed the diaghram on the diverter valve - and both ch and dhw censors . no joy . Ranenheat told me over phone its probably the heat exchanger - at 200.00 a pop ill replace the whole boiler ( 439.00 for the condensing equivalent from toolstation ) Wish I had invested in an antiscale device !

Jon Hinch, January 2009

Found this page searching to an answer to the exact same problem that I have! I hope Bri has fixed his by now. In my case I've isolated the fault to the diverter valve behind the hot water cylinder. Seems its sticky and a bit of pressure on the actuating arm completes the elec circuit for the boiler to start up.

Can I just replace the diverter valve with a new one? Is that a diy job? Would I need to drain the system?

Richard M, September 2007

either the diverter valve is sticking or the diapragm is split id go with changing the diapragm first ok

tony joint south wales, October 2006