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Problem - 3-pin Mobo Header, but 4-pin Fan Power (not molex)

Last response: in Components
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December 21, 2006 4:08:12 AM

I bought a barebones case that had an MSI mobo pre-installed. I saw it accepted Athlon 64 CPUs so I got one and a heatsink/fan that supported Athlon 64.

Problem is, during installation I see the CPU FAN header on the mobo is a 3-pin, but the cable coming off the heatsink/fan is similar but 4-pin. It is NOT a 4-pin molex.

What do I do now? I try searching for a 3-pin to 4-pin fan power converter cable, but everything I get back is a typical 3-pin power to a 4-pin molex.
December 21, 2006 6:14:10 AM

Quote:
Are you sure you have the right CPU cooler? Never heard of a 4pin non-molex connector for a CPU cooler.


I'm positive I have the right CPU cooler. I just took a closer look at the end of the cable and noticed the 2 white tracks on one side of it. By "tracks", I mean the guides that help the pin connect to the header.

On a 3-pin, those little tracks would be on the edges, but on this 4-pin, the on track is on the edge of the connector and the other is in the middle, right at the position of the 3rd pin. Which makes it obvious that I can connect it like that and let the 4th pin hole go unfilled.

Works just fine, although now I've got boot problems...time to head over to that forum section. *sigh*
December 21, 2006 7:13:32 AM

I have a similar problem but can fix it real easy. Got a CPU HSF I want to put on my GPU. GPU connector has 2 pins but nothing I can't change myself, I have some spares though.
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December 21, 2006 7:43:45 AM

LMAO that nobody could help you considering it's in a bunch of Tom's Hardware's newbie guides. Three-pin and 4-pin of that type are INTERCHANGEABLE.

The 4th pin on these new CPU coolers is for a new type of fan speed control. You can use it on a 3-pin connector just fine.

Only two pins are power (12v and ground), the third is RPM detection. The forth is for Pulse Width Modulation. So the third pin is not required for the fan to operate, and the forth pin is only required for PWM.
December 21, 2006 8:03:26 AM

In all fairness, I'm still running a socket A rig. Now I know bout this as well at least. I had to change the connector on mine though. Wanna put that badboy on my old 5700 and OC the $h!t out of it.
June 16, 2007 5:27:11 AM

When using these 4 pin fans on a 3 pin motherboard, does the fan run at the same speed all the time? I am using one like this now, and my fan speed does not go up when the cpu is under full load. This is causing my temps to go too high IMO. My opteron 170 idles at 38C, but hits 54C under full load. Is there some way to allow the motherboard to control the fan? Or if not, some way to manually speed it up?
June 16, 2007 5:44:24 AM

I have bad news: Some PWM fans will not run at full speed without the PWM signal. Others do. I don't know why this occurs. If your fan header is supplying the full 12V, I don't believe there's anything reasonable you can do to speed up the fan.
June 16, 2007 5:50:48 AM

it should increase as temps go up, the mobo will just adjust the voltage across the "12V" wires according to the rpm, well, most do...
June 16, 2007 6:14:33 AM

Crashman,
Nice to see you posting. I thought the forumz were completely abandoned. I know your on the dole, but it's still nice to see you come in and slap people around, except me. :wink:

@OP, You might try dropping the $7.00-$15.00 on a 3 pin fan. Problem solved.
June 16, 2007 12:52:19 PM

there are such adaptors available in my local computer stores
June 16, 2007 12:55:02 PM

I think you're confused. The later part of this discussion is about the PWM wire, not the 12V and ground wire.
June 16, 2007 4:04:38 PM

I have been watching the fan monitor in Asus PC Probe, and the fan runs at ~3500 RPM regardless of temperature. I don't think this is full speed, because when I first power on I can hear it running a lot faster.

My heatsink fairly large and has heatpipes, so I didn't think I would have to get a different one. I looked at the arctic cooling freezer 64, and it also has a 4 pin connector. Any suggestions for a good cpu cooler that has a 3 pin connector?

The Freezer 64 says it is backward compatible with 3 pin motherboards. Does this mean it would run full speed all the time, or be adjusted by voltage?
June 17, 2007 2:30:01 AM

I think the only thing u have to do is select another FAN for your original Heatsink, and u don't have to buy an entire new cooler. You can set your Fan at full speed in BIOS.(But I am not sure this works on your MoBo :(  )


Here are some Fan-Choosing Steps of mine for your reference:
First, u should make sure the size of your FAN, 8025, 9225 or 1225...

Secondly, choose a reasonable rotation speed of the FAN for you. (But I strongly recommended a FAN with less than 0.5A because some MoBo can't support Fan current greater than 0.5A otherwise it will cause damage)

Finally, find a suitable FAN either in local market or in an on-line store.


There are some great FAN brands available: (all of them are offering 3-pin connector FANs)
PAPST, NMB, Comair-ROTRON, Delta, SANYO, Nidec
June 20, 2007 8:01:38 PM

I have a Freezer 64pro with a 4pin power connector. My mobo has the 3 pin connector. It appears to be compatible with Cool n Quiet. I hear the fan spool up every once in a while when i'm gaming and the temps go up. So it works just like it should; quiet when its not stressed and cool when the fun cranks up.
June 21, 2007 2:35:16 AM

Thanks for that info. I was thinking of getting a freezer 64 anyway, and if for some reason it doesn't work properly with my mobo, I could get a PWM compatible fan controller.
!