My Thermostat is on Crack

I love fall.  But with the awesome weather comes some not-so-awesome thermostat fiddling.  You know, because it's cold in the morning (I need heat!), then warm in the day (uh oh, too hot-better flip on the a/c), then cold at night again (and back to the heat).  Not that I'm constantly flipping back and forth-I try to either hold out when it's too cold and don a sweatshirt and/or blanket, or just stay a little bit warmer than I would like.

But yesterday it was cold in our house at the kids' bedtime, so I decided to turn on the heat.  Now our downstairs vents are still closed (because we've been mostly on a/c, and if the vents are open then I would have to wear a parka).  I thought nothing of it, because the thermostat was set to turn itself off after reaching a certain temperature.  Pete and I watched a show, exercised, etc.  When I came upstairs, though, I felt like I was stepping into a sauna.  The temperature?  83 degrees!

WHY did the thermostat not kick off?  Dude.  It's done this every once in a while (like three times ever), but I've caught it before it gets too high.  So then I flipped it to a/c.  And...it did nothing.  So then I forced it to blow cold air.  We also opened a few windows to try to cool it down even just a little bit.  We slept with the windows open, which means that this morning-you guessed it-it was freezing cold in our house again.

But I didn't dare touch my thermostat, because I didn't want it to do the weird stay-on-even-though-I'm-supposed-to-turn-off thing.  Also?  I don't know where it senses what temperature it says that it's at.  There are times when I am boiling, and it says it's 66 degrees, and times when I'm shivering under a blanket when just the air in the house should keep me warm enough on its own.  What's up with that?

My only conclusion: crack.