Honeywell RTH6400 - Troubleshooting Common Issues; Blank Display Solutions; Temperature Setting Issues

Operating Manual
69-2211EF—05 20
In case of difficulty
If you have difficulty with your thermostat, please try the following suggestions.
Most problems can be corrected quickly and easily.
Display is blank • MakesurefreshAAalkalinebatteriesarecorrectlyinstalled
(see page 15).
Temperature
settings do not
change
Make sure heating and cooling temperatures are set to acceptable ranges:
• Heat:40°to90°F(4.5°to32°C).
• Cool:50°to99°F(10°to37°C).