Searched the database for a similar problem with no luck. Issue with '06 MCS is that a couple of months ago we noticed fan (high speed) was kicking on after shutting down the engine. I know and have read here that that is common and normal, but for us it has not been common or normal over the years. I replaced the fan due to loss of low side fan a couple years ago with a fan from RockAuto. We have noticed the fan only comes on after shutting down when the AC has been running - no AC running, fan never kicks on.

Today, stopped by parts store for new wipers (AC had been running). When I came back out to the car and cranked it, I had a temp sensor light and temp needle pegged at 250 degrees (hadn't seen this before). Shut it down, puzzled, and decided I'd go ahead and replace wiper blades while it cooled down. Fan immediately kicked on, as I'm sure it was supposed to in this case, and ran for about three minutes or so. Blades replaced (took 5 minutes max), cranked it up - no temp light and needle was sitting right where it always seems to be, straight up at about 200 degrees.

It was about a 10 minute drive to the house, so to troubleshoot, cranked AC full cold, ran car kind of hard, and the needle never moved off 200. Low fan seemed to be running at stop lights (no high speed anyway). Pulled into garage with temp still 200ish, and the fan did not kick on, which does not fit the pattern over the past couple months.

I do not drive the car often, but my daughter drives it daily and has verified fan only comes on after shutdown when AC has been running and not when AC has been off. The light and pegged needle are something new.

Coolant level is normal/good w/ no leaks. AC blows as cold as it always has. Is it possible that it is just a bad sensor? Any input is appreciated.