Those are indeed crazy readings.
I would measure between the positive battery terminal to a solid ground, such as the frame.
Even 20 volts would be way too high (assuming a 12 volt system) and 375 would be deadly.
Are you sure you are reading DC volts set to the correct voltage range?
@ceorl good ol car. Battery ordered. Thanks!
@b4cks4w
That is perfect! ;)