UK based. Worcester-Bosch combi-boiler (Greenstar 25si combi Mk IV). Pin timer.
Our problem is we can only get the central heating to turn on by setting the timer wheel (and obviously the thermostat).
The boiler has an off/timer/on switch and it doesn't matter if the switch is on timer or constantly on. We still can only get the heating to come on by setting the pin wheel to "on" at the time we want the heating on.
Hot water (on demand) works perfectly.
Thermostat seems OK, too - if not a little stiff to change temperature. The heating seems to regulate when on.
Any ideas what might have broken?