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Why cant fans operate in both directions?

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So when you mount a fan, the airflow goes in one direction, and to change the direction you need to unscrew the fan and turn it around. I wish you could just make the fan spin in the other direction, so clockwise instead of anti-clockwise, so then your airflow would push rather then pull, or vice versa.

Or would that not work? Maybe it doesn't, otherwise fans would be made to do so right?

Reason for this is when i install a rear fan in my case, i would prefer it bringing in air from outside the case, but to do that i need to have the "ugly" side of the fan visible, the side with the frame support and motor and cable visible, when the other side is just the sleek and simple fan blades which give a much nicer look. So i have the rear fan sucking air out atm just because it looks nicer for my system haha.
 
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Most fans are built with single direction blades. This allows the manufacturer to make the fans more silent and efficient. I have seen some fans that have a magnetic clip on them so you can flip the entire fan assembly, but not sure how good they are.
 
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Technically speaking, they could. A DC motor can operate both directions via flipping the positive and negative around. Fans only go one way simply because that's how they were designed. Pretty sure if you swapped the positive and negative leads, a diode on the fans PCB wouldn't allow it.
 
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Reason for this is when i install a rear fan in my case, i would prefer it bringing in air from outside the case, but to do that i need to have the "ugly" side of the fan visible, the side with the frame support and motor and cable visible, when the other side is just the sleek and simple fan blades which give a much nicer look. So i have the rear fan sucking air out atm just because it looks nicer for my system haha.
Mount the fan externally so it is blowing in to the case. Problem solved.
 
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Processor Intel Core i7 9700KF @4.4
Motherboard Gigabyte Z390M Gaming
Cooling Noctua NH-U9S / NA-FC1+Noctua and Be Quiet! Fans
Memory Corsair LPX DDR4 32GB 3200MHZ
Video Card(s) Asus Dual RTX 3060 12GB
Storage Samsung 970 EVO 500GB NVMe
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Audio Device(s) A] Onboard > Logitech Z623 B] Denon DRA-295 > JM Lab Cobalt 810
Power Supply EVGA G+ 650W with APC 1400VA UPS
Mouse Asus Strix Carry + Corsair MM300
Keyboard Ducky One 2 TKL MX Silver
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Interesting idea.
 
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