Abstract: A hand-held probing device is adapted for use in testing the existence and amount of electrical potential in an automobile engine block or other object under investigation. The device has a specially formed housing from which extends a probe and a ground lead at opposite ends. The housing also includes a voltmeter and an electric bulb connected in parallel between the probe and ground lead. The housing also includes a switch which enables the device to be operated while held in one hand thus enabling the other of the user's hand to be free and usable for other functions.