Thanks to you and woodz428 for the info.
I checked the shaft, the play is within specs and the "teeth" are lined up. After I reaasembled it it ran great for about 5 minutes and then it acted up again. I let it cool down ( it is -17C here ) and it worked again for a few minutes and then acted up again.
It would appear that the heat is causing it to go flaky, so replacing the sensor would seem to be in order.
[ February 13, 2003: Message edited by: CET ]</p>