MB Urquattro temp gauge help request

["Jouko Haapanen" <joukoh@vtoy.fi>]

The more I watch my temp gauge on the Urquattro, the more I wonder if
something is not right.  The temp will run at or just below normal on steady
highway speeds, but on long uphill sections where the cruise control opens
the throttle some more to retain speed, the temp gauge quickly shuffles over
to the right, eventually to start flashing.  Once the ascent is over, the
gauge quickly returns to normal.

The gauge does not exhibit this when the car is driven hard, but when the
increased load is steady and long.  Even at the track, I never saw the temp
gauge approach hot in the summer, but today at sub-freezing temps, running
around 100km/h on cruise the gauge started flashing after a very gradual
500m climb in 5th gear.  Weird.

Where does the gauge pick up the temp?  Bad gauge?  Bad sensor?  Bad
$omething el$e?

Jouko Haapanen
Pori, Finland