An electrophotographic image forming device according to one example embodiment includes a replaceable unit having a toner reservoir, a rotatable shaft positioned within the reservoir and a magnet in the reservoir movable in response to rotation of the shaft. A magnetic sensor is supported by a housing that is mounted to a stationary frame of the image forming device. The housing is movable relative to the stationary frame between an operating position of the magnetic sensor and a home position. In the operating position, the magnetic sensor is positioned to sense the magnet during rotation of the shaft. In the home position, the housing is positioned in a path of insertion of the replaceable unit into the image forming device and the replaceable unit contacts and moves the housing from the home position to the operating position during installation of the replaceable unit into the image forming device.