Outside temperature indicator

[LGREGF@aol.com]

The outside temperature gauge on my 1987 5000Q has gone bonkers.  Currently it
reads about 15 degrees F below the actual temperature.  Since the car spends a
lot of time on the road to Vermont, I miss knowing more accurately when the
outside temp is +/- freezing. Seems to also affect the internal thermostat as
well. Since I still haven't solved my ABS problem, this has the potential to
put the wrong type of excitement in my driving experience.  Re-booting by
battery disconnect has had no effect.  Any ideas appreciated?  Thanks.

Regards, 
Greg F.
'87 5KQ