Chattering Thermostat

[eggpasta]

Hi,

I am hoping someone can help me out. I have for the first time this autumn turned on my heating, and have been faced with an odd problem. I have searched the forums but cant find anyone having anything similar.

I have a standard glow worm conventional boiler

With the controller set to hot water on and heating off my room thermostat relay chatters continuously and the heating is continuously on even when the thermostat is set to minimum . Once the heating is turned on then the chattering stops and the thermostat will function as intended.

Basically, I am up to the task of swapping out the thermostat as I can get a straight like for like replacement, but before I splash any cash on something I may not need and just get a plumber in, I thought someone on here may be able to shed any light either way, and give me some clues whether it is something I could attempt myself or just bite the bullet and get a plumber in.

TIA

 

[eggpasta]

Think I have sorted it, although the water was on the OH went to run a bath and no hot water hence I gave the 3 way valve a good slap and it changed position, things are cooling down now and no more chatter on the stat

Still a little confused as to how this would have caused the stat to chatter in the first place so if anyone has any suggestions it may explain things as to whether my stat is on the way out.

Also if my 3 way valve has stuck once is this the beginning of the end and should I look to getting it replaced or see how it goes?