Boiler not switching off

[simonpdl]

I've got a Worcester 240 combi which used to switch off when it reached a certain temp. Now it just runs permanently until the timer switches it off. Is this a thermostat issue? And is it easy to change?

 

[jackthom]

Have you tried turning the room thermostat up and down to see if it clicks ON and OFF and if so does this have any effect on the boiler at all?

If you are confident with electrical repairs it's easy to replace but note that it carries mains voltage.

 

[simonpdl]

I don't have any room thermostats so I presume that boiler has an internal thermostat as it used to switch off and on.

 

[methaneman75]

surely it must be going off when the overheat stat trips, otherwise it would just boil, turn into steam and burst heat exchanger