This happened to me also. When I first got my car, my father picked me up and he must have hit the seat heater button by accident. It was a warm day and when I got in the car, the seat was red hot. The button is in a bad location. Very easy to hit by accident. I think he was trying to adjust the seat and he hit the seat warmer button by accident.So I was borrowing her minivan and she was using my Malibu over the weekend. She calls me and says, "The seat is getting hot! How do you turn this thing off?!?!?"
Whoops... I hadforgotten to tell her about the heated seat option (not like we'll ever have much need to use it down here). She must have bumped it on.
After talking, she found the switch for the seat heater.
Also, in my opinion, you don't need the seat warmers with the ultralux seats. The seats never get really cold in the winter time and the few times I used the seat warmers, the seats got way too hot - even on the low position.
This feature is really for use on leather seats. Not a necessary feature for the ultralux. Even on the coldest days, I never used it. I was really surprised that they included this feature on non-leather seats. I don't think that any other cars offer this feature on non-leather seats.