Malleus
Far west of Siegen
FWIW, these sensors can be checked with a multimeter, when removed. Just check for voltage change when a steel part is moved in front of the sensor face. If it's a wiring problem, and these are really easy to break at the potted junction at the rear of the sensor due to the age, the meter won't show an increase.
And for the good of the group, the early sensors are not compatible with the later models ('95 and up).
And for the good of the group, the early sensors are not compatible with the later models ('95 and up).