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Use a 2-pin ATX fan on a 3-pin mobo PWM controller?

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August 6, 2013 6:32:17 PM

I have a spare 120mm fan lying around, and I want to use it in my case, but it is too loud at full speed. I tried soldering a 150 ohm potentiometer to it, but the fan draws so much current, that the pot gets kinda warm. It's probably fine, but it's not the ideal way to do it. Plus, it would be neat to be able to control this fan using software.

The fan uses the v+ and ground from a standard 4-pin ATX power cable. Could I solder these to v+ and ground on a 3-pin motherboard fan connector cable? I know the 3rd pin is for sending RPM info back to the motherboard, and this fan does not have that capability. Is this required? Would the PWM still work, using SpeedFan of course (not the BIOS fan speed controller), even without the RPM wire?
August 7, 2013 7:49:47 AM

Zac Lloyd-Jones said:
Take a look at this. I have a feeling that should do what you want it to, minus the PWM stuff. It feeds off the 12V molex and splits to 2 12V and 2 5V fan headers.

http://www.ebay.com.au/itm/DC-4Pin-Molex-to-4x3Pin-5V-1...


I'm not sure I understand... So I guess the fact that those exist mean this WILL work? I recognize the little white cables coming out of the molex, but what are the black ones? And it says 12v/5v? I'm pretty sure this is a 12v fan, what voltage are the mobo connectors then?
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August 7, 2013 3:43:42 PM

I think that if you use the 5v header the fan should run slower, providing that its enough voltage to get it started up.
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