Abstract: A method and apparatus for detecting a short circuit across a Vacuum Control Switch by electrically connecting the apparatus to that side of the Vacuum Control Switch which should be dead at anytime the Vacuum Control Switch has manually been placed in the off configuration, and utilizing the arcing and shorting voltage felt there in the event of a malfunction to produce a signal to actuate visual and audio alarm circuits. More particularly, the invention is intended for use with Vacuum Control Switches placed in very high voltage circuits such as industrial furnaces. Its primary purpose is to prevent personal injury by warning maintenance personnel of a malfunction which could produce lethal voltage on components that would be expected to be without electrical voltage whenever the Vacuum Control Switch is in the off position. The apparatus is not independently powered for detection, but utilizes that voltage which is felt on the off side of the open Vacuum Control Switch by virtue of the malfunction.