# Dell 4/5Pin Fan Question



## 2 Bunny

Hey there all. I've got a Dell branded computer (Optiplex 745) which has a very large, but seemingly noisy CPU fan. It's not too bad, but I'm pretty sure that normal 120mm fans aren't that loud. It also happens to be that I've got an extra standard 120mm fan sitting around. I checked in the case and found that it can fit perfectly (even though it isn't as thick as the original, the diameter is identical), but the silly motherboard has that dell 4/5Pin proprietary fan port instead of a normal one.

From what I understand based on the writings and pictures in this thread, the red represents the normal 12Volts cable, the black represents the ground, and the white is the "rpm" that would normally be the yellow cable on a regular fan. The problem is that there is an extra wire in there, a blue, which is a "mystery extra". I read on Wikipedia that it has something to do with changing the speed without changing the voltage. My fan is just a standard regular old 3pin fan. Is there any amount of splicing I can do to get this fan to work on that board while letting the computer still adjust the speed?

Thanks.

- 2 Bunny


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## Wrench97

Dell uses proprietary components, look in the bios to see if you have the option of turning off the CPU fan Failure warning, if you don not buy a replacement Dell fan is the best route as using a 4 wire will constantly nag you about a fan failure.

Cleaning the fan and cooler as well as replacing the thermal paste may also go a long way in quieting the fan down(by reducing the RPM it runs).


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## 2 Bunny

*COUPLE QUESTIONS Reply*



Wrench97 said:


> Dell uses proprietary components, look in the bios to see if you have the option of turning off the CPU fan Failure warning, if you don not buy a replacement Dell fan is the best route as using a 4 wire will constantly nag you about a fan failure.


I'll have to take a look at that. I was just wondering if there was any way to splice the new fan on without it running full blast 24/7. From the Pinout, it looks like the RPM sensor is the only thing going back to the board (unless it can sense voltage and stuff), so no matter what, it shouldn't yell at us as long as we leave that pin connected, right?



Wrench97 said:


> Cleaning the fan and cooler as well as replacing the thermal paste may also go a long way in quieting the fan down(by reducing the RPM it runs).


I actually did apply some oil to it back when it was really loud and very squeaky, and it did get rid of the squeakiness and some of the noise, but not all of it.

Interesting that you should mention that though, because I was thinking about those softwares that tell you the RPM of the fan and stuff. Is there any way to know the minimum RPM that the computer will let it go in the first place to know if this would be worth it or not? Because the fan seems to spin at what I think might be "the minimum" from boot and all the time no matter what you're doing.

Thanks.

- 2B


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## Wrench97

Not on a Dell the software won't support the way Dell does it.
As for the pinouts that's for a standard board not a Dell board.
The Dell 5 wire fan has a temp sensor in it.


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## 2 Bunny

*ALL THESE FANS AND PINS Reply*



Wrench97 said:


> Not on a Dell the software won't support the way Dell does it.


Actually, I did some digging and found that a program called "SpeedFan" can tell the RPM at least of the fan. Currently, it reports about 830RPM. The software also offers some limited controls in 5% increments, but the fan only seems to recognize "slow" and "hurricane force" at 100%, where it hits around 2,000RPM. Are these typical speeds? If so, can they be slowed below 800?



> As for the pinouts that's for a standard board not a Dell board.
> The Dell 5 wire fan has a temp sensor in it.


Oh. In that case, here's one for a Dell. I don't see any temperature sensing in it though. That fourth pin has to be that "control signal", since the other three are already taken, and it's only a four pin fan.

Is there any way to splice a standard 3Pin fan on a four pin connector, or would it just run at full blast all the time because that fourth pin was what was controlling it?

- 2B


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## Wrench97

Is yours a 4 pin or a 5 pin?
The 4 pin can substituted with a standard 4 pin pwm fan, the 4th wire returns the speed to the motherboard sensor, the 5 pin Dell has the temp sensor on it.
If your bios allows you to disable the fan warning then yes you can use the 3 wire in not no you can not.
As for the rpm 8xx is already pretty slow the difference between 800 and 835 should not be noticeable plus will cause the CPU to overheat, leave it on automatic.


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## 2 Bunny

*REPLY TO LAME REPLY WITH UNCREATIVE TITLE REPLY Reply*



Wrench97 said:


> Is yours a 4 pin or a 5 pin?
> The 4 pin can substituted with a standard 4 pin pwm fan, the 4th wire returns the speed to the motherboard sensor, the 5 pin Dell has the temp sensor on it.


But can you substitute a standard 3Pin fan? Or would it just run at "full blast Hurricane Force" without the voltage control?



Wrench97 said:


> As for the rpm 8xx is already pretty slow the difference between 800 and 835 should not be noticeable plus will cause the CPU to overheat, leave it on automatic.


Actually, this thing has a small modest Core2 Duo 1.8Ghz and a truly massive heatsink that you'd have to see to believe, that's why I was wondering about slowing it more. The temperatures look very chilly with 800RPM.

Thanks.

- 2 Bunny


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## Wrench97

Read post #6


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## 2 Bunny

*HURRICANE FORCE Reply*



Wrench97 said:


> Read post #6


I did, but



> If your bios allows you to disable the fan warning then yes you can use the 3 wire in not no you can not.


didn't exactly answer my question. I mean, can I splice the 3Pin fan onto the 4Pin connector and not run at "hurricane force"? 

Thanks.

- 2 Bunny


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## Wrench97

You do not have to splice the wires just simply plug it on to 3 of the pins.


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## 2 Bunny

*FASTNESS Reply*



Wrench97 said:


> You do not have to splice the wires just simply plug it on to 3 of the pins.


But without the fourth control pin, won't it run at full blast all the time?

- 2B


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## Wrench97

I guess there's only one way for you to find out, hook it up. I stated at least twice that if your bios has the ability to turn off the fan warning it would work.


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## 2 Bunny

*Q Reply*



Wrench97 said:


> I guess there's only one way for you to find out, hook it up. I stated at least twice that if your bios has the ability to turn off the fan warning it would work.


Well, since I'd be using the onboard fan connector, this shouldn't even be an issue. How would doing that make the fan run slower anyway?

- 2 Bunny


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## Wrench97

It has to do with what your bios is capable of, Dell Bios that allows you to change the fan warning will run the fan on a 3 pin connector, those that don't allow the change, buy the Dell fan.


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