Honeywell RTH7400 series - Troubleshooting Common Issues; Display is Blank; Unresponsive Controls or Temperature Issues

RTH7400/RTH7500 Series
21 69-2222ES—05
About your new thermostatIn 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
• Check circuit breaker and reset if necessary.
• Make sure power switch at heating & cooling system is on.
• Make sure furnace door is closed securely.
• If thermostat is battery powered, make sure fresh AA alkaline
batteries are correctly installed (see page 19).
No response to
key presses (or
temperature will
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).