[93fxdl]

most wiper motors have a set of parking contacts which tell the motor it has reached the end of its travel and it sounds like this has failed
just had a look at mine and behind the multiplug there are some wires which connect to the backplate of the gearbox and i would check there first but if you take it apart it is possible there may be little parts that can fly out if all is ok there then you should check any relays for the wipers but since all other functions are ok imho i doubt this but then i am just a enthusiastic fiddler so what do i know
best of luck glenn