It looks like "HunterF12" posted about this exact problem two months ago, but no solution was posted.
I am currently doing my second attempt at building a wind simulator for use with iRacing and other racing sims. It utilizes an arduino uno, adafruit motor shield, ac adapter, and two cpu fans. I have followed every step precisely, done a good job (decent) on the soldering, but in the "shake it motors effect profile," clicking "test" under speed doesn't power the motors at all. Below is a link to the tutorial at the point where they upload the sketch and test the fans. On the motor shield, the power light is green and on. On the uno, the on light is on and green, and the L, TX, and RX lights are on, not flashing, and yellow. Thank you in advance for any help.
This has been mindbogglingly frustrating and, given this is my second set of uno and motor shield, and the cost of 3D printed parts, increasingly expensive. I have a multitool but am still learning how to use it. If someone could help me with the settings, I could maybe test the m1 and m2 outputs to see if power is going to the fans?
Hi !
2.3 board should be the same, have you tried manufacturer test sketch : https://learn.adafruit.com/adafruit-motor-shield-v2-for-arduino/install-software#running-the-example-code-2045935-8 , that's the fastest way to ensure there is no issue with the board.
Also maybe a simple issue, have you mapped the "wind" effect on the channel ?
Depending of the inertia of the fan a simple "channel or short effect test" may not be relevant, in this case i would suggest to enable static wind effect and disable the "run only in race" option so it will generate a permanent output for easier testing, if you configured it properly you will see a permanent output here : 
Nicolas
Ive got exactly the same problem and followed boosted medias video to a T and i have also replaced both arduini and ada fruit boards INCASE THERE WAS AN ISSUE and no success still 0v dc on the motor output of the ada fruit when testing . there is no mention in any videos of updating drivers . wish this link was simple its anything but and totally confused me trying trying to update software. https://learn.adafruit.com/adafruit-motor-shield-v2-for-arduino/install-software#running-the-example-code-2045935-8 /p>
PLEASE HELP as i cant let it go as it should work