Wiper Motor - its spins or swivels?

[BigSky71]

I recently got a used wiper motor from a parts supplier when I was ordering some other parts. I went to install it last night and either I don't have it installed correctly, or maybe the motor isn't working correctly...

The motor when activated spins in one direction the arm attached to the wiper linkage [both slow speed and fast speed work this way]. Problem is the linkage at the wipers binds up before one revolution of the arm can be made. My old wiper motor has been dead for so long I can't remember if it stopped and started to move the wiper linkage or just spun in one direction. I know the remedy is simple, but I haven't figured it out... Any suggestions?