TEMP. LIGHT GOES ON ALL THE TIME!

[AUDI1OO@aol.com]

The temp. light on my 91 Audi 100 always goes on when I drive the car.  The 
temp. gauge reads a normal temperature.  I never smell signs of engine 
overheating.  The coolant level is where it should be.  What else can be 
wrong?  Can it be that the fluid is old, and needs to be flushed and 
replaced?  Maybe the fluid isn't cooling as well as it should be?  Is this 
possible?  Any suggestions are greatly appreciated.  TIA for any help.

Nick