I have the same problem, and my mechanic told me that the sensor can go bad and the entire coolant reservoir needs replaced. Is this true? The level in my reservoir is where it is supposed to be, and the light comes and goes intermittingly.
Our 2001 Escape does the same thing. I believe the sensor in the coolant tank needs replaced, but I see no sense in spending the money to replace it. I just check the coolant level once every other month to make sure.