Wiper motor parking up??

My wipers were working fine, just slow, so I took out the motor. I only opened the cover on the gears, cleaned and re-greased them and put the cover back on. I did not move the gears or the arm etc. When I re installed the motor and hooked it up it now parks the wipers in the up position. I do not know why. Any help appreciated????
On the good side they do move more freely smoother and faster.