Room thermostat not connecting to CH boiler

[Glyn1959]

Hi my room thermostat (old type) clicks when I turn it but does not stop the boiler heating the rads whatever temperature I choose.
Photos attached. Any ideas please. All connections to the thermostat are clean and tight

 

[CountryFan]

Just the one thermostat? Do you have any test equipment? Is this a new problem or always happened?

 

[Glyn1959]

Probably a long time but my son has only just told me! Only a “live” tester.

 

[CountryFan]

Not sure what a live tester is. If it's a voltstick or similar it won't help. It could be the thermostat has failed, it could be the link is left inside the boiler. Probably going to need a gas safe registered engineer for this one. For the time being you can select hot water only on the boiler to cease firing when heating isn't required

 

[gas112]

does the heating go off when the clock/programmer is set to off

 

[Glyn1959]

No it stays on

 

[gas112]

No it stays on

it will be a faulty motorised valve then , not the stat

 

[CountryFan]

it will be a faulty motorised valve then , not the stat

I thought that, hence me asking if more than 1 stat, but looks like a combi?

 

[gas112]

I thought that, hence me asking if more than 1 stat, but looks like a combi?

i missed the pic of the combi

 

[gas112]

with clock off and stat turned down can you put a pic up of front of boiler and what its doing.
And as per country fan do you just have one stat as in you dont have separate controls upstairs and down stairs or underfloor heating ?

 

[Glyn1959]

Next time I’m at the property I will take a pic.
Only one room stay and no underfloor heating.
Would the individual stats on the rads influence anything??
Thanks

 

[ericmark]

This video

explains how the motorised valve works. 5:37 shows the switch, the thermostat or programmer works the motorised valve, and in turn the valve works the boiler, so if the micro switch sticks, the boiler will not turn off.

My boiler had the same problem, I unclipped the head, gave it a sharp tap on the cupboard base where the valve is hidden, and it freed off and has been working for a year without sticking again.