HI, Re: the honeywell Chronotherm III . all summer it has been at 64 degrees... now that is September and colder.. I went to press arrows up to warm up the house. Came back a few min later and all was gone from the screen but the words: Repl Bat (replace batteries). So even though we had just replaced them not to long ago and at the time we did the whole screen did not go blank we preplaced again.. It still shows those words only. So with that my question is, What has happened? thank you, Julie