Check Guages light

I have just purchased a 1993 chrysler Lebaron Sedan six cylinders 149,000 miles and it seems to run fine. However, when I tuen the engine on the Tachometer does not work at all and a light comes on that says check guages. The company I bought the car from told us that they recently replaced the alternator. Can any body tell me what might be wrong with the car and if the new alternator might be at fault?
Thanks: Wayne