Old British Gas Up2 thermostat doesn’t turn off heating

[Delia]

Hi,

I have British Gas thermostat UP2 for 10years, worked very well. I turned heating on yesterday as it was a bit cold. The hot water is in timer , but the heating advance and once button didn’t work , only select the ON button, the light is on and heating comes . But the heating won’t turn off even I select the off . Anyone can help me please?
Thank you

 

[ianmcd]

you will have a 3port valve (Y plan) or 2 x 2port valves (S plan ) post pics of what you have probably next to the HW cylinder

 

[Delia]

you will have a 3port valve (Y plan) or 2 x 2port valves (S plan ) post pics of what you have probably next to the HW cylinder

Thank you @ianmcd
I still couldn’t figure out which one is thatvalve .

 

[Madrab]

On the pipework, usually around where the pump and pipework is (as suggested usually next to the hw cylinder), would look like one of these.