I have a 97 Grand Prix GT with a 3800 engine. The “low coolant” light comes on occasionally, I checked the coolant in the radiator and reservoir, both are fine. I replaced the radiator cap. There are no signs of engine overheating. Could it be the thermostat? Also where is the sensor located?
It’s not the thermostat, but it could be the sensor. Don’t know where it is, but I’d look at the coolant overflow reservoir.
The sensor should be in the radiator. I believe it would be normally closed because it is sensing the ground through the coolant. When the level gets below the sensor, it has no more ground and opens the switch causing the light to go on. The sensor might be getting crusted up and not able to transmit the ground anymore (you are changing your coolant regularly right?). Look for a wire connected to the radiator about a quarter of the way down. One thing I ended up doing is simply clamping a grounded aligator clip to the sensor to shut the stupid thing off instead of replacing it.
Adding To What Bing Has Said, My Information Indicates The Level Sensor Is Located In The Passenger’s Side Radiator Tank And Is A Square Shaped Gizmo Held In Place By A " Snap Clip ".
Unplug the wires and to unlock the sensor, lift one leg of the snap clip from its locked position and pull outward with a slight twisting motion.