Reset procedures vary widely depending on the model of the Honeywell thermostat, but they include pressing System to reconfigure the settings or temporarily inserting the batteries backwards. Call the Honeywell technical support line or refer to the thermostat's manual for exact reset instruction for a particular model.
To perform a hard reset on a Honeywell programmable thermostat, switch the device off before using a coin to push open the battery door via the small slot. Take out the batteries, and place them back in so positive poles are touching negative terminals and vice versa. Leave them for a full five seconds before removing them and placing them back in the correct way. The display screen of the reset thermostat should initiate at this point.
Reset the system settings of Honeywell VisionPRO TH8000 Series thermostats by pressing System on the screen, and selecting the settings to be adjusted, such as heating, cooling, automatic operation or emergency heating. Save all changes by pressing Done. Reset the fan by pressing Fan in the screen's upper left corner, adjusting the settings before pressing Done. To reset the clock, press Clock near the bottom of the screen, and use the up and down buttons to choose the appropriate time.