3 pin to 4 pin conversion for CPU fan?

vbimport

#1

Hey guys,
I"m looking to replace the stock CPU heatsink and fan on my Dell i5 desktop. Unfortunately due to the case dimensions, there isn’t enough space to put a Cooler Master Hyper 212 Plus on the chip. So I have been looking around for something that is both shorter and effective. It looks like up the Zalman CNPS 9500A cpu fan/heatsink combo is pretty good and it will fit in my case at only 125mm height. The only potential problem is that it has a 3 pin fan connector to the mobo, while my stock fan is a 4 pin fan.

This leads me to 2 questions:

  1. Can I put a 3 pin fan connector on a 4 pin spot and have the fan work without having to do anything funky in the BIOS or have any problems?

  2. Are there 3 to 4 pin adapters for this sort of purpose? So far my searches keep pulling up 3 pin to molex 4 pin.

Thanks in advance.


#2

Hi,

4 pin fans are controlled by PWM, whereas 3 pin fans are controlled by voltage. At least you will have to modify some bios settings at least to adjust the fan control method. If there is no option to switch from PWM to the other method, then you should stick with a 4 pin PWM assembly. Otherwise anything can happen.

Michael


#3

I think the four pin connectors are set to accept three pin fans. The three pin socket of the CPU cooler should only fit on the motherboard pins one way. I think the CPU fan will run at full speed all the time since it only has three pins.


#4

Putting a PWM-controlled 4-pin fan on a 3-pin header should be fine. Given that the motherboard was designed with 3-pin connectors, you stand a chance of still having automatic fan speed control (the motherboard likely adjusts the voltage on the fly, unless your machine sounds like a wind tunnel at all times :bigsmile:). I can imagine Zalman’s design respects most setups.

In some instances, the fan controller on the motherboard may not supply enough voltage at boot, meaning the fan won’t start; turning off fan control should provide a crude workaround. Another option would using a direct connection to the PSU with an adapter to feed signal information back to the motherboard. (The latter would prevent the motherboard from thinking there is no fan and entering an error condition).


#5

[QUOTE=Albert;2652612]Putting a PWM-controlled 4-pin fan on a 3-pin header should be fine. Given that the motherboard was designed with 3-pin connectors, you stand a chance of still having automatic fan speed control (the motherboard likely adjusts the voltage on the fly, unless your machine sounds like a wind tunnel at all times :bigsmile:). I can imagine Zalman’s design respects most setups.

In some instances, the fan controller on the motherboard may not supply enough voltage at boot, meaning the fan won’t start; turning off fan control should provide a crude workaround. Another option would using a direct connection to the PSU with an adapter to feed signal information back to the motherboard. (The latter would prevent the motherboard from thinking there is no fan and entering an error condition).[/QUOTE]

Albert, its a 3 pin controlled fan with a 3 pin female connector. The mobo has a 4 pin header. I do see some 3 pin to 4 pin molex connectors but I was hoping not to go to that route.


#6

Ohh, haha, my mistake. It’s one of those days. :wink: I ended up searching for the plain CNPS9500 AT manual, and that does have a 4-pin connector (according to the manual), which confused me.

Is there a reason you choose the 9500A (LED version?) over the 9500AT? Are the dimensions as significantly different as the manual seems to suggest? Looking at the manuals for each, I find:

AT: 90mm (width), 115mm(length), 135mm(height)
A-LED: 115mm(width), 88mm(length), 128mm(height)

…I guess those few millimeters make a difference, eh? :doh:


#7

The A-LED version has $20.00 rebate and is available in Microcenter. Which makes it about $10 cheaper than Amazon with shipping.

According to Amazon and Newegg, the both have 4.9inch/125mm height measurements.


#8

The 4th pin is definitely the PWM-controls. A 3-pin fan will run constantly at one speed while a 4-pin PWM fan can vary its RPMs based on BIOS settings, temperatures, etc.

Kind of a letdown, huh? I was first cackling with the “anything could happen!” warning, thinking maybe your computer would be turned into a helo-powered box, flying around the room because of an errant fan at 30,000rpm, maybe chasing you 'round and 'round.

Boy - I never get to have any fun!


#9

[QUOTE=ChristineBCW;2652668]The 4th pin is definitely the PWM-controls. A 3-pin fan will run constantly at one speed while a 4-pin PWM fan can vary its RPMs based on BIOS settings, temperatures, etc.

Kind of a letdown, huh? I was first cackling with the “anything could happen!” warning, thinking maybe your computer would be turned into a helo-powered box, flying around the room because of an errant fan at 30,000rpm, maybe chasing you 'round and 'round.

Boy - I never get to have any fun![/QUOTE]

Well rather than provide you with tales of my liftoff box, and to make sure that I had the proper LGA 1155 brackets, as well as to avoid a long train trip I ended up buying the AT unit. Should be here tomorrow in all its shiny, coppery goodness. One thing I like already is that it doesn’t have those pain in the ass push pins.


#10

Let us know if it works out for ya. :slight_smile:


#11

[QUOTE=yojimbo197;2652614]Albert, its a 3 pin controlled fan with a 3 pin female connector. The mobo has a 4 pin header. I do see some 3 pin to 4 pin molex connectors but I was hoping not to go to that route.[/QUOTE]

My experience has been that the tab on the four pin connectors located on the motherboard is offset to one side to accommodate three pin sockets from the fan connector. Here is a photo illustrating the offset:

The offset tab configuration forces the three pin sockets to be connected properly.


#12

Thanks guys. I’m still on the steep end of the learning curve when it comes to computers. This will be only my 3rd heatsink I’ve put in. If this one goes well, I might buy another for my parents XPS 8300.

PS, when I read that whole computer longevity thread, I thought it was nuts to go into the case every month to clean the dust out. Until two days ago. I can’t believe how much dust had accumulated in 1.5 months after my last cleaning. I can only imagine the horror that will confront me when I go home at Thanksgiving.


#13

Yojimbo, I had sugarplum fairy dreams last night, all about a helo-powered PC buzzing around the head of some faceless guy who’s just moved into his girlfriend’s place. “And me, with no tools!!” is all this phantom was screaming as he swatted and ducked. Buzzzzz… zzzzztttt… buzzzzz… zzzzztttt-!

Surely this was all a coincidence.

(Hubby yells out, “A sick SICK coincidence, born in a demented mind…” You can see how he’s not the most supportive of mates, yes? That’s OK, though - he’s still chained to the dungeon wall.)


#14

Phew, installing the Zalman was more of an ordeal than I thought. The instructions call for installation of bolts underneath the mobo to anchor the heatsink. Unfortunately, what I didn’t realize was that Dell had “conveniently” fixed a standoff plate underneath the mobo to the mobo using some type of rivet. Then once I got everything back together again, applied the thermal paste to the CPU and the heatsink, and then mounted the heatsink on the CPU+holder. Only to have problems with the retention/crossarm that you are supposed to mount on top of the CPU. I repositioned everything and still the crossarm was pretty high in the air. Finally after looking at a instructional cartoon/video on Zalman’s website, i said f— it and bore down on both sides and screwed in both sides of the retention arm.

Believe it or not, right now after only an hour of run time at 90-100% CPU cycles I"m getting temps in the 54-58oC range. That is much better than the 65-70oC range I was getting. Time will tell if I get a “burn in” effect that lowers it. I"m happy enough with the temps I"m getting already.

Christine, there has been no liftoff so far. Just a lot of cursing, screw dropping, and scratching of my noggin. Perhaps it will occur after a couple of hours of usage…


#15

Top view of the Zalman CNPS 9500AT in action…



#16

Back view…
I wish the fan cord was a little bit longer but I managed to stretch it out.



#17

Front side
The Zalman has a 92mm fan. The copper looks really nice in this picture.



#18

At least these later Zalmans have rounded edges.

Those first couple were really sharp. I think they were originally sold on late-night TV - Ronco Bass-O-Matic-&-CPU-Coolers or something. “They slice, they dice and cool everything…”

Adding memory sticks meant phoning ahead and having an ambulance and bloodmobile nearby, just in case. “Was this why the Luke Skywalker Memorial hand-replacement technology was developed?”

Well, they weren’t so bad - chain-mail gloves covered by welder’s mitts did just fine.


#19

it looks real nice…

But I’ve gotta ask… which direction is the CPU fan blowing?

It appears you have it installed backwards?

Generally it’s best to have the CPU fan in a cooler like that
blowing towards the case fan which blows the hot air OUT.

the idea is to move the hot air OUT.


#20

Yes, Allan I understand that its best to blow the air out. The Zalman CPU fan is blowing directly into the case fan, which also blows out of the case. After a week of 24/7 running I"m still getting 53-58oC CPU temps at 100% load.