The LCD screen of my Honeywell CMS927 thermostat mostly stopped working.
See here how I fixed the display using a toaster.
(Also applies to the CM927 the S indicates it was sold with the receiver. The 921 is the 1 day rather than 7 day version.)

The site for user manuals:
https://heatingcontrols.honeywellhome...

I have another video with the background music removed here:    • Honeywell LCD fail and repair  no ba...  

Inspiration from:
   • Honeywell cm901 Thermostat Display re...