Honeywell Smartfit Room Unit Blank LCD

[Swheaton]

Hi,
We have a problem with our Honeywell Smartfit room unit, T8677B1006. It has suddenly developed a blank display on the LCD on the old unit.
We have checked the following;
Power to the Base Unit - 230v to the base unit,
Power at the room unit connection on the base unit - Yes 12v
Power supply to the room unit - Yes 12v
Checked for break in the wire from Base Unit to Room Unit - Yes all ok
We managed to find a new, old stock room unit, connected it hoping to fix the problem but the room unit LCD on the new unit is still blank!!
We are a bit stumped and have now just ordered a new old stock base unit hoping this will solve the problem.
Any input and help will be greatly appreciated
Thanks in advance
Simon

 

[Swheaton]

Quick update
We fitted the new Base Unit, connected everything and the room unit and boiler leapt back into life.
Apparently if the base unit isn’t sending info to the room unit, the room unit will stay blank.