Why does my Low coolant light stays Smoke blows through ac vents when ac is off and the engine is at normal running temp?

Most cars will not run hot if the radiator is a little low. It sounds like you may have a pin hole in your heater core (coil) and the stem could be coming through your vents. This should have some smell to it. Most cars will not run hot if the radiator is a little low. It sounds like you may have a pin hole in your heater core (coil) and the steam could be coming through your vents. This should have some smell to it.