Andrew, I tried this with red in terminal A and yellow in B but then had the problem described in my original post of the thermostat screen blanking out when trying to set the date.
Andrew, I posted a supplementary reply last night but then have continued to receive an email request to rate your answer every hour since, a total of 12 so far, not the best way to get a positive response.
I connected the wiring and then inserted the batteries, date screen flashed but as soon as I tried to amend the date with the up/down arrows the screen just went blank. I had not restored power to the thermostat. I removed the thermostat and replaced the old one, then inserted the batteries and it allowed me to adjust date as necessary.
Original wiring as in first post.
OK, can you wait?
Heating did come on with red and yellow connected, which suggests my thoughts on the wiring were correct.
Ok give me a few minutes to connect the new one
Same thing is happening, screen lights up and asks to set date, slider is set to date but as soon as the up button is pressed the screen goes blank and reverts to the factory set dye. The screen then lights up again a few seconds later and asks for the date to be set.
I have not put power back to the unit.
Haven't tried to go to installers menu, the instructions are to set date as the first action
OK thanks for the help.