Yesterday, the "Low Coolant" indicator on the dash lit. I checked the reservoir and it is not low. This morning the light is not lit and the car is cooling normally (as it had been). A cool front passed through here yesterday dropping the temp from the mid 80s to low 60s -- probably the lowest temp the car has seen since getting a new water pump and coolant about mid-summer. That's about the only thing I can associate with the appearance of the light. How is the low coolant lamp driven?