Funky outside temp display problem solved.
Yesterday, the outside temperature display on the C230 was locked at +15C. This was regardless of the actual temp being about 26C.
I called the dealer, and explained that the display seemed "locked." I had checked the sensor output through the diagnostics mode on the ACC panel, and the sensor was reading the proper temp, just not displaying it properly.
I shut the car off for a while, and came back. Same thing. Well, the dealer explained that they'd have to replace the sensor, the display, and a whole bunch of other parts.
Since they can't get the car in for two weeks, I thought I'd try something kinda novel. I pulled fuses 19 and 30, which are instrument panel fuses. I waited about 1 minute, and replaced them. Guess what? The outside temp display works just fine again. No problems encountered.
Microsoft would be proud! I just "reset" it...
1998 C230 "Black Betty"