How do I enable auto change over on the TH6110D1005, TH6220DXXXXX, TH6320U1000?
- To begin, press and hold the Up arrow and FAN buttons until the display changes.
- Press Up or Down to change settings.
- Press NEXT to advance to next function.
- Press DONE to exit and save settings.
ISU 12 needs to be set to 1 for Heat/Cool/Auto/Off to be available
If set to 2 the only system option will be Auto
If your thermostat does not have option 12 it is an older generation where this option was not available