Hi, I have a '99 saturn wagon. Recently the lights warning of engine overheating have started staying lit. As I understand, these lights are supposed to flash on when the car intially starts, but then only come on if there is danger of the car overheating. The lights have come on, though the car is sitting outside in sub-freezing weather, and the temperature gauge is still showing the car as being cold. Everything works fine, the heater and defrost all work normally.
Still, remove the radiator cap, when the engine is cool, and see if the radiator is full.
Besides a low level of antifreeze/coolant, this problem can be caused by “weak” antifreeze–i.e., antifreeze that has been diluted with too much water.
You need to investigate this situation because if the engine is really overheating, you are courting severe engine damage. With any luck, the problem is just a defective coolant temp sensor. However, you cannot assume that, and you need to have the situation evaluated by someone who is qualified.