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Is it fine to plug a PWM fan for the CPU in a chassis fan slot?


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#1
zxcymn

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Please read it all so you know exactly what I meant by the title.

Long story short I ended up with an extra fan so I decided to throw it on the other side of my Hyper 212 Evo to get a push/pull system going. My MOBO has two connections marked for a CPU fan, called CPU_FAN1 and CPU_FAN2. FAN1 has 4 pins like normal, but FAN2 only has three (which is pretty dumb, I think). My extra fan is kinda loud at full blast so I really would rather use all 4 pins. I looked and I only have one more 4 pin, but it's for a chassis fan, marked CHA_FAN1.

I know it's more than likely perfectly safe to plug the extra fan into those pins, but since it's for a chassis fan, will it accurately report my CPU temperature to the fan so that it can speed up/down accordingly? Or will it use a different temperature (such as ambient) to control the speed? I don't exactly know how that works, so I wanted to check here before trying it out.
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#2
Veeg

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Please read it all so you know exactly what I meant by the title.

Long story short I ended up with an extra fan so I decided to throw it on the other side of my Hyper 212 Evo to get a push/pull system going. My MOBO has two connections marked for a CPU fan, called CPU_FAN1 and CPU_FAN2. FAN1 has 4 pins like normal, but FAN2 only has three (which is pretty dumb, I think). My extra fan is kinda loud at full blast so I really would rather use all 4 pins. I looked and I only have one more 4 pin, but it's for a chassis fan, marked CHA_FAN1.

I know it's more than likely perfectly safe to plug the extra fan into those pins, but since it's for a chassis fan, will it accurately report my CPU temperature to the fan so that it can speed up/down accordingly? Or will it use a different temperature (such as ambient) to control the speed? I don't exactly know how that works, so I wanted to check here before trying it out.



Yes it will be fine,the chassis or system fan option is on most MOBO's..the 4th wire is just a sensor wire and you don't really need it,the fan will run fine on 3 wires..
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#3
zxcymn

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Yes it will be fine,the chassis or system fan option is on most MOBO's..the 4th wire is just a sensor wire and you don't really need it,the fan will run fine on 3 wires..


Sorry, I don't believe you understood what I meant. I want it to run on all four pins. It's a fan designed to be controlled by the CPU's temperature. Using only 3 pins, the fan stays at 100% speed and it's loud. I want it to be on a 4-pin connector so that it won't be obnoxious. The only 4-pin connector I have left is marked for a chassis fan. My ultimate question is do the different pin areas read different temperatures? Such as, does the 4-pin CPU_FAN1 read the CPU's temperature, while the CHA_FAN1 reads the ambient temperature?

I don't want to plug the CPU fan into a chassis connector unless I know that it will still accurately control the speed according to my CPU's temperature.
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#4
Veeg

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Only if your MOBO sensors are set up for any control and or temp monitoring... as i said it will not matter if you put one there it will work as an extra fan...done that myself for more air flow..
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#5
dsenette

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Yes it will be fine,the chassis or system fan option is on most MOBO's..the 4th wire is just a sensor wire and you don't really need it,the fan will run fine on 3 wires..


Sorry, I don't believe you understood what I meant. I want it to run on all four pins. It's a fan designed to be controlled by the CPU's temperature. Using only 3 pins, the fan stays at 100% speed and it's loud. I want it to be on a 4-pin connector so that it won't be obnoxious. The only 4-pin connector I have left is marked for a chassis fan. My ultimate question is do the different pin areas read different temperatures? Such as, does the 4-pin CPU_FAN1 read the CPU's temperature, while the CHA_FAN1 reads the ambient temperature?

I don't want to plug the CPU fan into a chassis connector unless I know that it will still accurately control the speed according to my CPU's temperature.

without actually getting down to the design specifics of your motherboard, if it's a speed controlled fan header (one would assume it would be as it's got the sensor pin...but, can't be guaranteed) then it's probably going to use a temperature sensor from the location it's allocated for. there's no logical reason for a chassis fan to use the CPU temp, though it might use the CPU temp if that's the only thermal sensor in the system. it would probably just use a different set point for speed.

you should probably check your bios and see what temperatures and fan speeds are reported, and which ones are controllable through the bios. this will give you a hint as to what you could expect from plugging a fan in to that header
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#6
Veeg

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You could use speed fan to see if it has a sensor and if speed fan picked it up..Or check your bios..

Edited by Veeg, 24 January 2013 - 10:02 AM.

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#7
Veeg

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Yes it will be fine,the chassis or system fan option is on most MOBO's..the 4th wire is just a sensor wire and you don't really need it,the fan will run fine on 3 wires..


Sorry, I don't believe you understood what I meant. I want it to run on all four pins. It's a fan designed to be controlled by the CPU's temperature. Using only 3 pins, the fan stays at 100% speed and it's loud. I want it to be on a 4-pin connector so that it won't be obnoxious. The only 4-pin connector I have left is marked for a chassis fan. My ultimate question is do the different pin areas read different temperatures? Such as, does the 4-pin CPU_FAN1 read the CPU's temperature, while the CHA_FAN1 reads the ambient temperature?

I don't want to plug the CPU fan into a chassis connector unless I know that it will still accurately control the speed according to my CPU's temperature.

without actually getting down to the design specifics of your motherboard, if it's a speed controlled fan header (one would assume it would be as it's got the sensor pin...but, can't be guaranteed) then it's probably going to use a temperature sensor from the location it's allocated for. there's no logical reason for a chassis fan to use the CPU temp, though it might use the CPU temp if that's the only thermal sensor in the system. it would probably just use a different set point for speed.

you should probably check your bios and see what temperatures and fan speeds are reported, and which ones are controllable through the bios. this will give you a hint as to what you could expect from plugging a fan in to that header


Kinda like i said in post #4
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#8
zxcymn

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I checked the BIOS and I can indeed set the chassis fans to be controlled by CPU temperature; they were all by default set to full blast. It's nice not having to listen to that obnoxious rattling anymore. Thanks for the replies!

Edited by zxcymn, 24 January 2013 - 12:52 PM.

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#9
Veeg

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Make sure you don't re-set them to the point your PC over heats..
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#10
zxcymn

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Make sure you don't re-set them to the point your PC over heats..


I highly doubt that will ever happen unless another fan fails again :)

I keep a close eye on all my temperatures and even during intense games the temps never go above 45.
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