Oil boiler problems, can you help?

[oilhead]

If you can feel no resistance to the manual lever on the valve, then it is in the heating position. Switch of all power to the boiler at the fused spur, and the diverter valve should close. If it doesn't, then sounds faulty. Take off the cover, and then release the synchron motor from the head and make sure the valve closes. If it does, then the motor is seized open and needs to be replaced. Available from most stockists.
If when you turn off the power, the valve closes, then something in the control circuit is holding it open, or the DHW stat is broken.

 

[Burnerman]

Maybe its just the powerhead that needs replacing on the DV - done a few of these.
John

 

[spraggo]

Ok well i will have to get someone out to look at it, but thanks for all your help, very much appreciated

It could also be a problem with the flow/proximity switch. This would be the case if the boiler does not fire when a hot tap is turned on with the heating switched OFF.