In a device for detecting errors in a charging line, the device detects an
error in the charging line connecting the vehicle generator and an
on-board battery. The device includes a bias circuit, a charging line
error detecting means, and a warning means. The bias circuit biases a
voltage of an external terminal receiving the power generation
instruction signal in the vehicle power generation controller with a
voltage of an output terminal of the vehicle generator. The charging line
error detecting means detects the error in the charging line based on a
voltage of an output terminal of the power generation instructing means
that is provided within the external controller and generates the power
generation instruction signal and a terminal voltage of the on-board
battery. When the charging line error detecting means detects the error
in the charging line, the warning means performs a warning operation to
give notification of the error.