Reverse direction of spin on a fan...

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coolchu001

Limp Gawd
Joined
May 27, 2007
Messages
506
Is it possible to reverse the spin of a fan?? (without reversing the case fan)
I have tried flipping the ground and 12v, the fan just doesn't work...Any ideas?
 
Short answer: no.

Modern PC fans use brushless motors. The electromagnet remains attached to the frame, as a circular magnet moves around it. Brushless motors have to switch the current through the elelctromagent to reverse polarity, keeping the fan spinning. This is usually done with a small switching transistor on the board. To reverse its direction, you would have to swap in a new IC that works that way. Alternatively, rewire the phases to pass current in the opposite direction. Either way is not exactly easy.

Besides, the fan blades are designed to work for one direction. Spinning them the other way will really reduce performance and just make a lot of noise.
 
coolchu001 said:
Is it possible to reverse the spin of a fan?? (without reversing the case fan)
I have tried flipping the ground and 12v, the fan just doesn't work...Any ideas?
Click to expand...

Why do you want to? Unless the fan is symmetric and specifically designed for flow reversal, it's not going to provide a good air flow when it is spun backward.
 
Well I modded my Sanyo Denki and the only way fofr this fan to fit is in current orientation, it is pulling in air through the radiator and I want it to blow out...
 
I think you'll either have to flip the entire radiator/fan or get a new fan. Like Brain Recall said most fans are made with specific leading edges and if that edge isn't being used as the leading edge (i.e. reversing the fan rotation) all you'll usually get is a really loud noisemaker.
 
dennisjai said:
The front and back is made differently? can't fix this with a simple flip?
Click to expand...

If you look at the cross section of a blade on a typical fan, you will see that the blade is curved so that it "scoops" the air and pushes it down. If you reverse the direction, the blade can't "scoop". It's kinda like getting ice cream with the back-side of a spoon; you'll get some ice cream that way, but you'd get more if it were turned over the right way.
 
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