# Can I "convert" a 18v fan to be strictly 12v?



## TechnicalFreak (Mar 17, 2010)

Sorry for bad english, but I have a Papst fan that was on a "machine" and is rated to 18v. I got it running on 12v, but it runs so slow.
The fan is a 140mm, dual ball bearings and is "brushless". 

I have managed to remove most of the fan details such as, the fan "blades" and so on just so I can reach the electronics of it. However, from that point on I have no clue whatsoever what to do.

I'll take a picture if anyone needs one. (At school right now)


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## tacgnol (Apr 9, 2010)

Why do you want to run it at 12v? If it's in your PC you can connect one wire to +12V and the other to -5V giving 17 volts which is almost 18 

I wouldn't try to mod the fan itself...


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## PVTCaboose1337 (Apr 9, 2010)

Putting a 12v and 5v line in series to make a 17v connection is a bad idea unless you have a voltage regulator.  Otherwise, your power supply with die.  You just need a 10 cent part.  Picture and link coming soon!


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## newtekie1 (Apr 9, 2010)

tacgnol said:


> Why do you want to run it at 12v? If it's in your PC you can connect one wire to +12V and the other to -5V giving 17 volts which is almost 18
> 
> I wouldn't try to mod the fan itself...



I'm pretty sure if he did that, it would give him 7v, this used to be an old trick to make fans run slower and hence quieter, before fan controllers were mainstream.


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## brandonwh64 (Apr 9, 2010)

a LT1170 switching regulator would work







source


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## PVTCaboose1337 (Apr 9, 2010)

newtekie1 said:


> I'm pretty sure if he did that, it would give him 7v, this used to be an old trick to make fans run slower and hence quieter, before fan controllers were mainstream.



CORRECT UNLESS you do what I say and get power from the motherboard (ATX power from the power supply).  








brandonwh64 said:


> a LT1170 switching regulator would work
> 
> http://obs.nineplanets.org/meade/1812/1812.gif
> 
> source



This is very clever!


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## tacgnol (Apr 9, 2010)

12 - (-)5 = 17v

If you use the +5v and the +12v you get 7v, if you use +12 and -5 then you get 17v.

I saw something about it a while back here:

http://www.afrotechmods.com/fanmod.htm

I would imagine with the amount of current drawn it won't do the PSU any harm, it definitely works but yeah a regulator would work too and is a less ghetto way to do it...


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## OneMoar (Apr 20, 2010)

a 18v fan will run on 12v just fine (albit at a slower speed)


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