Low Coolant Blinking - 94 Lumi Euro

Recently my Low Coolant signal has been blinking at me. As far as looking at the resevoir it has plenty enough coolant. Is it more likely the sensor is bad or loose, or I have a more serious issue? I haven't noticed the temp gauge go any higher than it normally does.

When my '91 did that same thing, I pulled the switch out to inspect it. It had brown crud on the probe. I drained the radiator, plugged in a new switch, refilled the radiator....problem solved. The switch was $21 at AutoZone, if I remember correctly.