Drayton Thermostat not turning boiler off

[Secret_Sipper]

We have an old Baxi Solo boiler which is will be replaced in the next few years and repositioned but until then I'm gonna have to try and keep her running!

Last night I noticed the temp getting warmer than normal. After turning the thermostat down (British Gas RS2 rebadged Drayton for 2 wire installs) noticed the boiler not knocking off. I also have a British Gas UP2 (Again rebadged Drayton) which has some funny quirks but I believe it's the way it's been wired (which is a different matter but I have to run both HW and CH together if I want the heating on, although I can run just HW if needed or turn the tank stat down)

Before rushing out to Screwfix to buy I've tried I few things which haven't made any difference. 1 being checking all the connections, turning the UP2 off and on. I'm not convinced but I think it's the programmer as the 2 wire to the thermostat is at 2.8v and 0v when switching, but assume it would be 240v? This doesn't alter the boiler state and continues to run regardless of stat position.

Any help would be appreciated if you've had this happen before yourselves before replacing bits.

Cheers

 

[Secret_Sipper]

Ok bit more info. Its decided to work again. The thermostat works NC with 240v at a lesser temp. Switching it to run gives 0v. I wasn't getting these voltages before so I'm edging my bets it's a relay in the programmer that's breaking down.

 

[CBW]

It could be the programmer yes, this is what would send the 240Vac to the stat.

 

[Secret_Sipper]

Thanks Chris for the confirmation. Glad I've been able get this far!