I see that VolvoKurt is experiencing some erratic temperature gauge readings, so I figured I'd add my experience as well.

Has anyone ever had a "good" temperature gauge bottom out while driving?

You see, while I was returning to school a few weeks ago, the temperature gauge needle dropped to nothing, where it normally lies when the car is off. Mind you, this reading came after at least an hour of interstate, 75-mph driving. A few minutes later, the temperature gauge went up to about midrange, perhaps a tad higher than 9 o'clock.

The only alternative to flaky wiring that I can guess is that the sensor did actually get cold. I don't know where it lies in the engine bay, but since I pulled the Aero headlights and put in the quad rounds, I don't think my front end is quite as tight as it used to be. I'm guessing there might be a little more airflow into the engine bay, as I did notice heat "waves" coming from the entire front edge of the hood while idling for a while at one point. With the old headlights, the waves would only come out through the grille area, not over the lights.

So, perhaps some good gusts of wind into the engine bay landed right on the sensor and chilled it for a while. Since then, there might have been one or two instances when the gauge was off, but it's been working fine otherwise, after it warms up in the cool weather we've finally started having. If I'm not right, though, I guess I might be bypassing the temp compensation board at some point.
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'89 244 GL -- 108,700 miles (see profile for info on car)