I've bought a cheap 12V 3-pin DC brushless fan a while ago. I didn't know much about why it had 3 pins instead of 2 when I bought it but now I know the third (yellow) wire is for measuring the fan speed. However, the fan does not spin when given the 12 volts between the black and red wires (ground and positive). It wobbles around a bit and then stops.
My first thought was that it's an AC 3 phase fan, but that makes no sense, first of all it clearly states "DC" on the fan, which could be a lie. Secondly, if it was an AC fan it would not wobble around at all when given 12 V, so what's going on here? Maybe I just bought a bad fan that doesn't work, maybe some of you guys know what's going on?