Room unit not functioning - Honeywell Smartfit programmer T8677B1006

Jan 17, 2024 Last reply: 2 years ago 4 Replies

Good evening and thank you for allowing me to join your forum. I'm pretty handy with most things but this is driving me mad !!! I have a Honeywell Smartfit programmer T8677B1006 7 Day Optimised Room Unit and the LCD display has stopped working. I have checked the voltage to it from the base unit and it is 12v. I therefore assumed that the unit was defunct. I sourced a new old stock direct replacement and expected it to work. Alas, it didn't work which I assume means that the fault is elsewhere. I have checked what I can on the base unit.



240v in and 12v out. The wire between the base unit and the room unit is good. What am I missing ??? TIA Ian Freezing cold in Cornwall !!!

Does it have batteries ?

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John T.

It's not clear what the "base unit" and "room unit" means in this explanation. Looks like this is UK. In the US thermostats are typically powered by 24V AC from the system transformer and/or batteries.

On Thu, 18 Jan 2024 04:55:16 -0800 (PST), trader_4 posted for all of us to digest...

Bingo! Batteries or bad transformer. Hard to tell over the pond...

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