Cooling system/check coolant light 95 wagon

Will someone please tell me what sensor drives the "check coolant" light on the dash cluster? My Chilton's manual seems to have forgotten to mention that. (Chilton's has been going downhill the last 15-20 years, in my opinion) Stupid light keeps flashing on & off even though the coolant level is fine & temp gauge reads normal. I do have a miniscule leak somewhere since I can smell coolant whenever I get out of the car after driving it, but the level never seems to drop. Hope I can find it before it gets worse. Are there any common places for tiny leaks to start? (Have the 1.9 motor)

Thanks!

The switch for the coolant light is inside the reservoir. You will see two wires going into the top of the reservoir. That's what they do. If you unhook the wires the light will probably go out.