the boiler operates the central heating but not the hot water ,however if cenral heating is on i get a small amount of hot water

dave, December 2009

Hi again, Steven is also correct. As I said a number of causes can result in DHW issues. Depending on the exact symptoms the solution is varied. If the fault is the DHW not firing up by itself then that is more likely the solution I mentioned. If your hot water fires up but then feeds the radiators and not your taps (this symptom gradually gets worse overtime) then its your diaphragm inside the diverter valve. They can be purchased for about £5. It will mean removing the diverter valve and stripping it to open it to replace the diagpram. You can purchase the whole diverter valve for about £50 if you shop around. This would save about a 1/2 hour of DIY time, if you are a competant DIYer it will take about an hour or so to replace the diverter valve.

Steve, January 2010

The diaphragm within the divertor valve could be worn
life span usually two years, when the hot tap is opened
the pressure against the diaphragm pushes out a pin
onto the microswitch calling the demand for domestic
hot water, if this diaphragm starts to split there is less
pressure to push out the pin, resulting in the microswitch
not being operated, part £20.00 and half hours labour.

Steven, January 2010

Hi Dave
I have had a similar problem and even though it may not be the solution to your issue it may help. I checked the diagnostic fault finding flow chart and it indicated 2 areas, firstly the microswitch and secondly the diverter valve. I checked and found two issues, namely, at the end of the diverter valve under the plastic casing (the microswitch and cover) the round shouldered plastic actuator had broken in half and was in two pieces, this would mean it could not switch to hot water, secondly the microswitch was intermittent, jiggling the two wires around it could make it work. i suggest you try this area first, its exactly as the diagnostics suggest and doesn't involve whacking the boiler at the top right hand corner as some alternative forums have suggested!!
Good luck

Steve, January 2010