Radiators won't cool down, no hot tap water

[loveaduck]

I have an Ariston 20/1 MPS Combi boiler, ageing but still in pretty good condition. No major issues recently.

This morning I discovered that the radiators were blazing hot, hotter than normal, despite the fact that they should have switched off (they were on a timer switch). When I switched off the timer switch at the plug, it made no difference. Also, I can't get any hot water, even though the boiler fires normally when I twist the taps.

Any ideas what could cause this strange behaviour?

 

[loveaduck]

I moved the function switch from 'Central Heating+Direct Hot Water' to 'Direct Hot Water only' and now the radiators are cooling down and I have hot water through the taps again.

Any ideas? Thanks.

 

[gas4you]

DV sounds as though it was stuck in ch position