What car is it? what are the symptons?
Most likely cause for failure of the outside temp. is the sensor, they are approx. £12-£14, and is fitted in the front bumper on the passenger side, most likely behind the lower small bumper grill.
If its reading wrong check that it is located properly whet its meant to be, we see a lot that read higher as that have fallen in behind the bumper & get the heat from the engine
Hi,
As your car is quite early you might not be able to change just the sensor with early vehicles the sensor is part of a cable assembly that runs from the bumper (sensor) to the back of the cluster, but do enquire with MB as I,m unsure at what point they changed to a replaceable sensor.
That is of course if the display is ok, and not bled as the above post suggests, but if its just a blank screen then it can still be the sensor at fault.