Problem Worcester Bosch Boiler!

[ecpcsb]

Ok guys, got a tricky one for you.
I have a Worcester Bosch 240 BF Boiler.It's been serviced fairly regularly and the last service was about 18 monthsago. I fitted a room thermostat and connected this to the boiler a few yearsago and all's been working well.
A couple days ago I noticed I wasn'tgetting any hot water. Checked the boiler and there was no power to it. Checkedall the fuses and found a small fuse on the PCB to be faulty, so I replaced it.So I then had power. I also checked the diverter valve and that was still ingood condition.
The pilot light was off, so I re-lit it. Theswitch for hot water was on, but when the tap was opened the boiler didn’t fireup. I could hear the little click you get when you create demand and I couldhear the pump, and when I turned the hot water switch off the pump stopped.
Now the only way I can get hot water, is byrunning the tap, switching the hot water switch to on, lighting the pilot andby doing so the boiler fires up and hey presto I have hot water. As soon as thetap is closed though, the boiler fires down and the pilot light goes out.
Another thing that’s puzzling me, is thateven with the central heating in the off position, when the boiler fires up forhot water, all the radiators get hot too. This may be a red herring, butthought I’d mention it.
Any ideas?

[ecpcsb]

Just noticed something else. When I can get the pilot light to stay alight, if I flick the switch to turn the hot water on, the boiler fires up without any tap being open!

[diamondgas]

ecpcsb ... You need someone qualified first of all as it sounds like you have an issue that may become dangerous! If the burner is on without any demand then that isn't safe!

Radiators heating up on water only indicated a problem with the diverter ... If it's stuck that could be the reason why there appears to be a demand when there is not! The pilot could be going out because the boiler is overheating! It will if the flame is staying on and the pump is turning off! There are other possibilities but they are the most likely culprits I'd say!

Old boiler now however, do you want to be trying to keep the old doll going or is it time for something new and much more efficient? that's your choice of course! Seen plenty on here spend fortunes keeping old boilers running when in reality replacement is the best option! IMHO