rosalie, actually, the motor is doing exactly what it is supposed to do. It does turn "full circle". It is actually your windshield wiper linkage that cause the arc movement of the wipers. Check oo your Olds to see if that is in working order and not binding anywhere. Once you remove the motor, see if you can move the wipers by moving the linkage or vice versa. Here is how to remove the linkage:"
Disconnect the negative battery cable.
Remove the wiper arms.
Remove the shroud top vent grille.
Loosen (but do not remove) the drive link-to-crank arm attaching nuts.
Loosen the two nuts, then separate the transmission drive link from the wiper motor crank arm using tool J-39232 or equivalent.
Unscrew the linkage-to-cowl panel retaining screws and remove the linkage by guiding it through the access hole in the shroud upper panel.
Some models you will need to unsnap the two water deflectors from the transmission assembly.
[http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0996b43f8039382b|source]
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Hope this helps, good luck