Not batteries, the buttons simply don't work no matter how hard you press them to change temperature. Known fault with the earlier CM927 thermostat. It has to be at least 10 years old by now. The display gradually packed up on first one and the current one was a replacement by Honeywell as it...
Hi,
We have a next to useless Honeywell CM927, very old no longer available, the temperature buttons no longer work so adjusting temperature is impossible as they got harder and harder to press to make changesand finally gave up.
The thermostat still turns the boiler on/off but cannot change...