Valiant help

[jctilingservices]

Hey guys,
I am just after a bit of help/ advise, my mother has a valiant combi boiler, not sure what model, but its about 10 years old and it gets serviced every December, within the last 2 weeks it has been displaying an intermittent fault, with the room thermostat turned off, and no hot water running ( she is just sitting watching tv on her own ) all of a sudden the room feels warm, she gets up and feels the radiator and its warm /hot, same in back kitchen, unsure about upstairs rads as she never checked those. Could anyone shed any light on what could possibly be causing this.
Thanks in advance

 

[picasso]

Usual cause is the diverter valve passing when the hot water preheat kicks in, the boiler cant reach temp so keeps running heating the rads, turn off the preheat till the diverter valve is replaced.

 

[jctilingservices]

Cheers for the reply mate, appreciated