Why is this warning light showing up on my car?

I have a 2000 Ford Taurus Wagon.

For some reason I can’t parse, the “Low Coolant” light keeps popping on. My coolant is absolutely not low (I’ve neurotically checked it about a thousand times). I cannot find any evidence of a coolant leak. The temperature gauge is not showing the engine reaching any sort of even kind of dangerous heat even during long trips, and even with ambient temperature in the low 90s.

If this is just a touchy/overactive sensor, is there any way to stop it from reading false positives? I’d like to not have to disable it, lest the radiator fail at some point and I actually need the warning.

My go-to mechanic is a retired old dude. He’s good, but he doesn’t charge for diagnostics, and I would rather not take up time he could be making money on exploratory surgery. He likes me because I figure out the problems before I come to him.

Thanks for the help.