I have a question about DC fan, such as the ones inside a computer.
I was discussing with a friend and he told me than when you clean such fan with a vacuum cleaner, you should block the fan so it doesn't turn (which I never did), because it could damage the motherboard (which never happened to me). He couldn't explain to me because he isn't into electronics.
I replied that it didn't matter because there was most likely some protections inside the fan (such as a diode?), which disallowed any power to be sent back into the motherboard.
After testing with my multimeter connected to the wires of a disconnected fan, and using the vacuum cleaner to make it turn, it appears that there is a small amount of power being generated and sent into the wires. I tried with 3 different fans, same thing. I knew fans could be used as generators, but I didn't expect computer fans to be like that.
Why is that? And what happens when computer is shut down and the fan is still turning for a while?
Sorry for noob question!