Circuit fault detecting device and method

摘要

To detect accurately an insulation fault in a load circuit, Power supply lines and an electric heater (a load circuit) are connected by a detecting portion to detect a detected voltage (detected value) in accordance with the magnitude of a leakage current Id that flows through a ground between the power supply lines and the electric heater, and an evaluation as to whether or not there is a breakdown of insulation of the electric heater relative to the ground is performed by an evaluating portion based on the detected value obtained when the relay contact points are open.