Circuit Description

The defogger switch is a momentary switch to ground. The Intelligent Switching Unit (ISU) monitors the status of the defogger switch. The ISU energizes the internal rear defogger relay when it detects a change of status in the defogger switch. The ISU de-energizes the internal rear defogger relay when it detects the next change of status in the defogger switch or a predetermined on time interval has elapsed.