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Since turning the heating back on our hot water has cooled down to minimal heat and the radiators do not get hot at all even when the stat is turned up full, boiler was checked over when heating was put back on as it wouldnt light shortly afterwards, this was the fan and now it lights no problem, heat was a problem before this but as weather was still ok we did not realise until after the engineer had left so couldn't ask him! boiler is fine and the pump feels as though it is working as it does slow down when turned to a lower speed and hums quietly. heat in the pipe before and after the diverter valve is the same (not hot at all) so I don't think it is this, hot water does get properly hot when immersion is switched on though. Could this be faulty tank stat or room stat? or both? What I can't understand is if one of the stats are faulty why is it affecting both hot water and rads? the boiler is an ideal and is only 4 years old, pump, stats, diverting valve are all also only 4 years old, timer seems ok. system has a cold water feed to a tank in the loft and all rads have been bled to no avail, any help will be appreciated. :cry:

The logical explanation is that the boiler thermostat is either set too low or faulty. There is a slim possibility that you have poor circulation which is preventing the hot water from leaving the boiler and reaching the radiators. When the pump is running and the boiler has "reached" it's temperature, feel the feed pipes as close to the boiler as possible. If they are red hot, suspect a flow problem. If cool, you have a boiler problem still.

We finally had the boiler man look at the boiler and he found a small circular thingy (tube like) which was faulty, apparently they don't often go but it was stopping gas getting through to the boiler after the initial burst and then cutting it off. A warm house and hot water at last! best of it was the part was only £10 and total price fitted was a very reasonable £47.