This evening I was going to take care of a few quick maintenance items on my 240:

1.) Replace the air filter,
2.) Clean the air mass meter,
3.) Clean the idle air valve, and
4.) Clean the throttle plate.

Of course, along the way I was going to check for any leaks in the system, and clean out the accumulated junk that gets in the air box. When I opened up the box I noticed that valve controlled by the thermostat was in the "open" postion, it was 81 degrees outside, and the car had not be running for over 24 hours.

What I know: If it is hot outside and the flap is closed, it will open if you place an ice cube on the thermostat. If it is cold outside, and the flap is closed, if you use a cigarette lighter or hair dryer on the thermostat, it will open. I also know that it usually fails in the open position, and that a lot of people just plug theirs up, so as to avoid a roasted AMM.

What I am wondering is if anyone knows the operating temperature range for this thermostat? I'm wondering if maybe mine is not operating correctly? It seems like it should be closed if it is 81 degrees outside. I'm going to tear into it tomorrow after work when it is nice and hot outside (should be 95-100 or so) and see if it is closed.

The current thermostat is about 2 1/2 years old and was bought from FCP. When I applied heat to it (gently, from a cigarette lighter) it closed.

Any replies would be appreciated.
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If it needs to be maintained, repaired or replaced on a 1990 240, I've probably done it. '90 240DL, 249K looking forward to 300K badge (or sticker??). >>You haven't really worked on a car until you draw blood<< :-}