Fanuc Magnetic Sensor Error

[symage]

I have a Fanuc 6M control with a Magnetic sensor for spindle orientation. I frequently get sequence errors because the spindle has difficulty finding orientation in order to tool change. Is there a way to tell if the problem is with the sensor, amplifier or board without paying Fanuc a gazillion dollars for the new parts? Thanks

[Mitsui Seiki]

Does the sensor have a diod so you tell if it's affected?A green or a red diod. Or maybe it shows both colors.Not at the same time of course. Turn the spindle by hand and see if it lights up.If you see two colors(Red and green)the red shows first and then the green.Maybe the sensor is too far away from the cam.
9 times out of 10 it is the sensor.