[Birdhunter1]

Bird this is a simple question, but when was the last time you changed the batteries in your T-stat? I have seen that right there cause some strange problems, but usually the stat doesn't work at all if the batteries are bad. (reminds me I need to change mine)

Only other thing I can figure is if your unit is in the sun it will work harder, but you said it has worked fine for years up until recently.