Bosch worcester 70/90 won't turn off

[stephen85]

Oil central heating at my parents house has started playing up last few days

It's a bosch worcester 70/90 burner, basically it won't turn off, say we put heating on for an hour well after we turn it off at the time clock the boiler keeps running, so no lights on the time clock at all but the system is still running

What could be causing this problem?

Basically we have to go out to garage and turn it
Off at the mains, and when we switch it back on later it will fire itself up again, it's like something is over riding the controls and keeping it on constant.

Any help would be great cheers

 

[stephen85]

Anyone?? Any idea why a boiler wouldn't shut off??

 

[Terrywookfit]

Sticking motorised valve for starters.

 

[Boilerman2]

1) as already said Sticking Motorised valve actualtor
2) Boiler in Garage? incorrectly set Frost Thermostat
3) Faulty Programmer - just because the LED's go out does not necessarily mean that the outputs are shut down

A methodical examination of the system will be required, using a multimeter to prove voltages etc
Happy hunting!