The main thing I learned was to take it to the mechanic when the condition was happening, that is bring it in when the fan wouldn't shut off. In my situation the condition only happened ocassionally so when I brought it in the mechanics were only guessing at the condition and ended up replacing a lot of things (for a lot of money) that were probably OK. The last time I brought it in with the fan on, the mechanic was able to fix it. He didn't go into great detail about the cause (something about a problem with a wire), and I didn't press him.