A window heating apparatus for use with an automotive vheicle including a vehicle battery, an internal combustion engine, a transmission, and a generator for generating an output voltage corresponding to engine speed. A voltage regulator is switchably connected to the vehicle battery and, when connected, controls current to the field winding to maintain a constant generator output voltage. A heating element is provided for heating a vehicle window when connected to the generator output terminals. A signal indicative of a demand for heating the vehicle window and a signal indicating when the transmission is in neutral or park are provided. A circuit normally connects the generator output terminal to the vehicle battery and the voltage generator. The circuit, in response to a command signal, connects the generator output terminal to the element while disconnecting the generator output terminal from the vehicle battery and the voltage regulator. The command signal, which is produced in response to the vehicle window heating demand signal, is interrupted except when the transmission is in neutral or park to avoid excessive voltage which might damage the heating element. While the command signal is present, engine idling speed is controlled to change the generator output voltage delivered to the heater element, dependent on vehicle-compartment temperature. Also while the command signal is present, current to the field winding is interrupted if the generator output voltage exceeds a predeterminedd value.