Thermostat not working properly

[altondykes]

Trane tcont802as32da thermostat when programmed the wake, leave, & return temps all change correctly, but the sleep temp dose not change , but when you check the setting the sleep setting is blinking and the correct temp is *

[Freon]

How old is the thermostat.

Did it ever work correctly.

Who installed and programmed it.

[altondykes]

Thermostat is about 10 years old; Installed and programed by the installer and it has worked properly. This the 3nd thermostat since the unit was new.

[Freon]

Since the thermostat has worked properly and assuming you have made no changes to the system, then I would try replacing the batteries as a last attempt. Unless there's an obvious change in your system, it seems the problems you face could be due to the thermostat especially since you're replaced it 3 times. You might review all the installer settings in case one has become changed by an act of a poltergeist.