BMW Repair: Thermostat, losing coolant, accurate gauge

Question
Within 10 minutes from cranking 1991 325i, the temp. gauge was reading HOT. What problems am I looking at? I have a feeling that it's the thermostat. Was replaced about three years ago. Within the past 3 days, temp gauge has been reading hotter and hotter, gradually. My SI Board wouldn't make the temp gauge read hot, it would just not work, right?

Answer
Depending on if you are losing coolant.I doubt its a thermostat.I would have an accurate gauge and check the temperature.Check the temp of the radiator and all the hoses.If one is hotter than the other it may be  blockage in the cooling system.Having other electrcal problems could make the gauges read false readings.