DUAL MODE WINDSHIELD HEATER CONTROL

摘要

A windshield heater element for an automotive vehicle is controlled to provide a maximum power deice mode of operation and a reduced power defog mode of operation. The deice mode of operation is initiated in response to an operator actuated deice command and is terminated in response to the first to occur of expiration of a predetermined time period after initiation, or an operator actuated off command. The defog mode of operation is initiated in response to termination of a preceding deice mode of operation provided that such termination was not in response to an operator actuated off command, or an operator actuated defog command. The defog mode of operation is terminated in response to the first to occur of expiration of a predetermined time period after initiation provided that such initiation was not in response to an operator actuated defog command, or an operator actuated off command. Further, the deice mode of operation is permitted only when the vehicle transmission is in the park or neutral state, and the idle speed of the engine is raised above the normal idle speed to ensure that the power produced by the engine driven generator is adequate to meet the combined power requirement of the windshield heater element and other vehicle loads during the deice mode of operation. Additionally, the energization of the heater element is terminated or prohibited in response to detection of an abnormally high windshield temperature condition, an abnormally low battery voltage condition, an abnormally low heater current condition, or vehicle ignition shut-off. Alternative embodiments employ three operator actuated input switches, and a single operator actuated input switch, respectively.