I just learned a lesson and thought I should share. If something doesn't work, check the voltage and continuity of the hookup wires before taking things apart.
I traded a smartphone with Josh for a robot claw. When I started to work with the claw, I could not get it to work. I took it completely apart to test the motors, and they were fine. After putting it back together, I started checking the connections and found that I had a broken ground wire... . Wasted a couple good hours all together.