BMW Repair: Temp on a 1986 BMW 325, coolant level, 1986 bmw 325

Question
My BMW has recently been "running hot."  The needle on the temp gauge goes past halfway but not past 3/4.  This has been happening just recent and with increasing frequency every month.  My coolant light is constantly on in the check display near the sunroof.  My mechanic says that I just need to buy a new sensor to allieviate that problem.  My question is, does this mean my engine is starting to tire(it has only 97000 orginal miles) or is it something that can be easily dealt with like a thermostat or water pump? I live in San Francisco where the weather is mild but inland can get very hot and it seems to be a long summer.
Thank You
David Garza

Answer
In the overhead the light is for coolant level, it has nothing to do with temp, unless the coolant level is really low in the reservoir. I wuld suggest thermostat be the first thing to replace and make sure that the coolant is not being lost somewhere.