Troubleshooting DC motor I worked on the starterkit project #9 motorized pinwheel, and the motor worked just fine.

I then tried to add a potentiometer, and now the motor won't rotate at all any more (neither in the current nor in the project's baseline configuration). I also tried connecting the motor to the 9V battery directly, to no avail.

I did check the battery by briefly connecting a LED right away. The motor apparently also still generates current if I turn it manually (checked with a directly connected LED either).

What else can I do to check what's wrong with the motor? Is it possible that I somehow accidently killed it with my attempts with the potentiometer?
If your motor doesn't work when connected to the 9V battery, either the battery is flat (which is likely since you were able to connect the LED without destroying it!! - they are a 2.5-3v part, not a 9v part) or the wiring to the motor is damaged. When you connect the motor directly to a 9v battery, it should turn pretty fast - may also work if you connect it to between 2 &amp; 4 AA batteries. 

9v batteries don't have that much energy in them... you would be better off with a battery pack with 6 AA batteries in it.