Abstract: A brush wear indicator for a dynamoelectric machine, such as a direct current motor, comprises a fiber optic conductor coupling an emitter and a detector. The fiber optic conductor is fed into a brush holder where it is supported by a spring holder to which is attached a coiled biasing spring. The fiber optic conductor includes a region of separation where an element actuated by the biasing spring operates to complete or interrupt a light path between the exposed ends of the conductor at the separation. In one embodiment, an angulated tab secured to the spring operates as a shutter to move in and out of the spring holder to complete or interrupt the light path, while in a second embodiment, a rubber flexible diaphragm having an inwardly projecting body portion is actuated by the spring, by moving in and out of said region of separation to complete or interrupt the light path.