Or, really what I'm asking is: "Did I screw up my wiper motor because I didn't bother indexing it before i reassembled it?"

The motor on my car started making the noise that is typical of separated magnets. I had a spare of unknown origin sitting around, but before I installed it I opened it up to take a look inside, at the magnets and electrical contacts. I think the rotor turned a bit as I put it back together.

Now, when I have the wipers set to intermittent, they run constantly, just like they were on low speed, and even when I shut them off they sometimes complete a few additional sweeps before stopping. Did I screw up how the motor is indexed, causing it not to park correctly, or is another cause more likely?