Abstract: A headlight warning system incorporates an engine running sensor and a headlight sensor coupled to a control circuit for activating a warning device, such as a buzzer, when the headlights have been left on for a first period of time after the engine has stopped running, and for deactivating the warning device either after a second period of time, if the engine is started, or if the headlights are shut off. The engine running sensor inductively senses a vehicle ignition signal. The headlight sensor magnetically senses the current in one of the battery cables using a Hall effect sensor in series with a magnetic flux collector encircling the battery cable. If the battery current exceeds an adjustable threshold, the headlights are assumed to be on. Following the deactivation of the warning device after the second period of time, the headlight warning system is reset by either starting the engine or by shutting off the headlights.