How to reverse fan rotation (answer: you don't)

Hi all,

For fitting reason I need to reverse fan rotation with my 120mm case fans. I tried to switch the red and black color wire and thought it would work. After I did that, the fan didnt rotate at all. I thought I burned the motor and then I switched the wires back to original position (red in the middle and black on the side) and it start rotating again.

I am confused because I thought reverse the + and - wires should make the motor (fan) rotation reversed. Unless fan manufacturer put some protection circuit to make motor only rotate one direction.

I would really appreciate any advise!!
Epox 8k3a+ (rev. 1.2)
AMD 2000XP
Corsair XMS3000 -- 199 @ 2-2-2-5-1
Kingmax PC2700 -- 180 @ 2-2-2-5-1
TwinMos PC2700 (Windbond chip stamping A version) -- fail @ 2-2-2-5-1
Samsung PC2700 (ATP designed; still waiting for Samsung original) -- 201 @ 2-2-2-5-1
CoolerMaster ATC210 modified with 8 fans
Thermalright AX-7 with Delta 80CFM
PC mods rheobus 4 channel fan controller (17W per channel)
digiDoc5 for temp hardware monitoring
2 x IBM ATA 100 HD
Toshiba 16x DVD and Pelxter CD-ROM

MV99

Many fans are polarity protected. Im curious why you didnt just turn the fan around 180* It will blow the opposite direction then.

If your looking to use two fans in a counter rotating fashion, I have not seen any fans for sale that can accomplish this.


PS If the fan wasn't polarity protected you may have fried it

Undo the screws, turn them around, better now?

The fans wont reverse rotation because they are built to not rotate when you accidently reverse the wires. It's a safety feature because nobody wants their fan rotating the wrong way. The fins are built to be optimized rotating in a certain direction. Change that direction and the fans will barely push any air at all.

Your solution: Take the fan out of the case and simply turn it around and stick it back in the case. This is the only way you would want to be able to reverse fan direction.

PS: damn you Sam! I was posting a reply to this in General hardware. By the time I hit the post button, it was no longer existing! Good thing I copied the text I wrote.

Thank you all for the advise.

I do know the simple way of just turn the fan and will get it done... However, one side of fan blade is almost flash with the frame of fan which will give me trouble.

The reason is that I originally had 4 fans installed on the side panel. The 2 on the bottom are 92mm intake fans. I am now trying to replace with two 120mm fans. With larger fan, one of them will be able to cover my OCed LeadTek Ti4600 and put a lot more cool air into case.

The problem is that I am little lazy to re-drill the hole again. I plan to just live with the holes I drilled for 92mm fan. In order to keep my aluminum mesh fan filter stick on the side panel, I need to use some screws and those screws will touch the fan blade. If I can reverse the fan rotation, I can have more clearance so the fan blade wont touch the screws (BTW, I have already used the smallest nuts for screws).

If I have no way to revese fan rotation. The only two solutions I can think of are -->

A. (harder way)--> make the hole bigger and perfectly fit for 120mm fan.

B. (easier way but not as pretty)--> put those standard fan guard to raise the fan and cut out few metal wires which would touch those screws and use tape to fix 120mm fan insde the side panel.

If anyone can give me better option it would be great!!!


Epox 8k3a+ (rev. 1.2)
AMD 2000XP
Corsair XMS3000 -- 199 @ 2-2-2-5-1
Kingmax PC2700 -- 180 @ 2-2-2-5-1
TwinMos PC2700 (Windbond chip stamping A version) -- fail @ 2-2-2-5-1
Samsung PC2700 (ATP designed; still waiting for Samsung original) -- 201 @ 2-2-2-5-1
CoolerMaster ATC210 modified with 8 fans
Thermalright AX-7 with Delta 80CFM
PC mods rheobus 4 channel fan controller (17W per channel)
digiDoc5 for temp hardware monitoring
2 x IBM ATA 100 HD
Toshiba 16x DVD and Pelxter CD-ROM

MV99

rewiring

the fan blades arent always curved. in most cpu fans, yes but not case fans.

the three wires are yellow 12volt black ground 12v and a 5v wire usually red. if you swap the black and yellow wires the fan will spin the opposite way. iv done this to create a turbine affect by monting two opposite spinning fans ontop of each other.
if there is a fourth wire that is your control line. alows you to conrol speed. but that wont alow you to reverse the fan


myspace.com/ematep

Ematep said:

the fan blades arent always curved. in most cpu fans, yes but not case fans.

the three wires are yellow 12volt black ground 12v and a 5v wire usually red. if you swap the black and yellow wires the fan will spin the opposite way. iv done this to create a turbine affect by monting two opposite spinning fans ontop of each other.
if there is a fourth wire that is your control line. alows you to conrol speed. but that wont alow you to reverse the fan


myspace.com/ematep

Click to expand...

Actually, on ANY 3 wire fan, RED is 12v+, Black is Ground, and yellow, green, or blue (depending on fan manufacturer) is RPM or "sense" signal...

4 wire PWM controlled fans are the same as above with the only difference of RPM or "sense" being green, and the PWM "control" signal being blue...

..This thread was bumped from 2002.

Still though, turning a fan around is really the easiest way to do this.

Oh god. I saw he had an Athlon XP 2000+ and a Ti4600 and I was like wtf?

I have to know...why in the world would you join OCF and, with your very first post, dredge up a thread from 2002?

hokiealumnus said:

I have to know...why in the world would you join OCF and, with your very first post, dredge up a thread from 2002?

Click to expand...

Yeah, I seen that as well, figured since he already posted, and put up the wrong info on the fan wiring, I'd respond and put up the correct info, so if some poor soul was searching and used the info, they wouldn't try wiring up a new fan and have something go *poof*...

Maybe they dont like the search feature, and were protesting of sorts?

PsycoPhreak said:

Yeah, I seen that as well, figured since he already posted, and put up the wrong info on the fan wiring, I'd respond and put up the correct info, so if some poor soul was searching and used the info, they wouldn't try wiring up a new fan and have something go *poof*...

Click to expand...

trying to change the direction of Arctic Cooling TC fan will quietly destroy it, no poof, just dies!

happend to me 5 min ago..

frodel70 said:

trying to change the direction of Arctic Cooling TC fan will quietly destroy it, no poof, just dies!

happend to me 5 min ago..

Click to expand...

While we appreciate new members using the search feature (not being sarcastic), this thread is from 2002.

Was going to say....only post in an 8 yr old thread lol...

funny thing is, this is the 2nd time this thread has been necro'd. I think reversing fan direction is an awful idea though...just turn the fan around pysically, the screws are easy enough to get out.

Quailane said:

Oh god. I saw he had an Athlon XP 2000+ and a Ti4600 and I was like wtf?

Click to expand...

I still have an Athlon XP 1700+ and a Ti4200 that's chuggin' along quite nicely.



btw...I love necro'd threads, they're a part of history plus it's cheap & easy time travel!

It's not doable, the hall effect triggers are in the wrong spot if the fan is turning the wrong way.

I think it laughable when people point out an older thread (what? got nothing better to do?) Information is information and information never gets old. Necro smeckro who cares go out in the yard and play.

The sensorless drives are "easily" reversed by switching two phases around. (If you could disassemble the motor and drive without destroying it, that is.) But the bigger issue of the blades having the wrong curve is basically impossible to fix.