Replaced Dell fan: BIOS no system fan detected. Workaround?

charred_water · Post by **charred_water** » Wed Aug 01, 2007 12:28 pm

I have an older Dell Precision 330 which I'm trying to silence.

It has a 1.5ghz P4 with has a green plastic housing ducting the airflow to a 92mm case fan connected to the motherboard.

I replaced the Dell fan with a Nexus fan, only to find that Dell uses a non-std motherboard fan connector. It looks like the Dell fan has a temperature sensor built into the fan.

I connected the Nexus to a standard PSU connector. The airflow seems okay compared to the Dell. I measured the air temperature coming out and it's close to what it was with the Dell fan. And the system is way quieter with the Nexus fan.

However, when I boot, the BIOS complains no system fan is detected since I'm not using the motherboard fan connector. The BIOS says press F1 to continue. The system boots normally if I press F1.

But I have to press F1 everytime I boot the system now! This is a pain.

Is there some sort of simple workaround to fool the BIOS? Can I plug in the old fan plug and connect a resistor or something to the fan plug so the motherboard detects a system fan?

Or am I stuck with the noisy Dell fan? If so, does anyone make quiet fans which are compatible with Dell motherboard/BIOS?

Thanks!

psiu · Post by **psiu** » Wed Aug 01, 2007 2:24 pm

It should just require a standard RPM sensing fan with the standard 3 pin motherboard connector.

Here's one from endpcnoise: http://www.endpcnoise.com/cgi-bin/e/std ... _92mm.html

charred_water · Post by **charred_water** » Wed Aug 01, 2007 2:40 pm

I installed this exact Nexus 92mm fan from encpcnoise in my Dell PC.

However, the 3 pin connector on the Nexus is not the same as the 3 pin connector on the Dell motherboard.

The Dell fan has a blue component, which I think might be a thermister or other temperature sensing component. I do not think the three wires on the Dell fan are the same as the three wires on the Nexus fan.

Does anyone know?

SebRad · Post by **SebRad** » Wed Aug 01, 2007 2:58 pm

Hi, the 3 pin Dell connection will take a "normal" fan in electrical terms, it's just the plug that's different. If you look at the dell fan likely the ground wire is black, the +ve may well be red, white is common for tach signal. With some work to splice the Nexus fan in to the Dell fan connector it should be fine. The Dellâ€™s Iâ€™ve seen have a thermistor sticking out the fan hub that controls the speed, donâ€™t think any control comes from the motherboard for the rear fan.
I once, temporarily, fitted the 92mm fan from a Dell desktop PC in to a Compaq server that's 120mm fan had failed and it refused to boot unless it saw a tach signal. The Dell fan worked ok until proper replacement came in, strongly suggests to me that fan is standard, just the connection that isn't.
Regards, Seb

alglove · Post by **alglove** » Wed Aug 01, 2007 2:59 pm

Here is what I did with my sister's Dell Dimension 8100 (1.4 GHz P4), which also has a "non-standard" fan connector and the "No System Fan" detected error message in the BIOS:

It turns out that the pinouts in the non-standard fan connector are actually exactly the same as the "normal" 3-pin fan connector. The only difference was the piece of plastic surrounding the 3 pins. Very carefully, I simply lifted the piece of plastic out of the motherboard, taking care not to disturb the 3 pins. Once I did that, I simply connected the standard 92mm fan to the naked 3 pins. Problem solved!

I would venture to say that the same "remove the stupid piece of plastic" trick will also work in your Dell.

Keep in mind that through the years, Dell has had a tendency to reverse the order of the fan pinouts... just to confuse everybody, it seems. For example, their P2-266 computers used such a "reverse pinout". My guess, though, is that the your computer will be just like my sister's, and use the "normal" order for the pins.

BillyBuerger · Post by **BillyBuerger** » Wed Aug 01, 2007 4:44 pm

I've had some old Dell's over the years myself. I believe the work-around for the "System Fan Failure" message is to turn off something like "keyboard errors" in the BIOS. You'll still get the message but it will just continue on anyways without having to push F1 or anything. If you do a search on the internet for the error message, I'm sure you'll find something more descriptive. But I know it's something related to keyboard errors. (yeah, makes sense.... keyboard.... fan.... same thing)

Bluefront · Post by **Bluefront** » Thu Aug 02, 2007 2:35 am

Here's the solution with pictures.....Link. Any three-wire fan should work in this situation with the small wire swap/mod.

"Additional notes: The connector on this fan is not a standardized 3-pin header. However it is wired correctly and will work properly in normal 3-pin headers, as shown in the following image. Owners of Dell PCs should inspect their old fan to be sure it is wired, as shown below from left to right, Black, Red, White. If it is Black, White, and Red instead, you will need to perform a very simple modification to the Red and White pins to swap their places in the housing."

charred_water · Post by **charred_water** » Thu Aug 02, 2007 8:45 am

SebRad wrote:Hi, the 3 pin Dell connection will take a "normal" fan in electrical terms, it's just the plug that's different. If you look at the dell fan likely the ground wire is black, the +ve may well be red, white is common for tach signal. With some work to splice the Nexus fan in to the Dell fan connector it should be fine. The Dellâ€™s Iâ€™ve seen have a thermistor sticking out the fan hub that controls the speed, donâ€™t think any control comes from the motherboard for the rear fan.
I once, temporarily, fitted the 92mm fan from a Dell desktop PC in to a Compaq server that's 120mm fan had failed and it refused to boot unless it saw a tach signal. The Dell fan worked ok until proper replacement came in, strongly suggests to me that fan is standard, just the connection that isn't.
Regards, Seb

This is very useful information. I assumed the Dell's were sensing the thermistor on the third pin and adjusting the rpm accordingly via the +ve.

Thanks!

charred_water · Post by **charred_water** » Thu Aug 02, 2007 8:50 am

alglove wrote:Here is what I did with my sister's Dell Dimension 8100 (1.4 GHz P4), which also has a "non-standard" fan connector and the "No System Fan" detected error message in the BIOS:

It turns out that the pinouts in the non-standard fan connector are actually exactly the same as the "normal" 3-pin fan connector. The only difference was the piece of plastic surrounding the 3 pins. Very carefully, I simply lifted the piece of plastic out of the motherboard, taking care not to disturb the 3 pins. Once I did that, I simply connected the standard 92mm fan to the naked 3 pins. Problem solved!

I would venture to say that the same "remove the stupid piece of plastic" trick will also work in your Dell.

Keep in mind that through the years, Dell has had a tendency to reverse the order of the fan pinouts... just to confuse everybody, it seems. For example, their P2-266 computers used such a "reverse pinout". My guess, though, is that the your computer will be just like my sister's, and use the "normal" order for the pins.

I can't wait to get home and try this trick. I'll be sure to check the order of the pins is not reversed. If I can't remove the plastic housing, I will follow the other suggestion to rewire my Nexus fan to the Dell fan connector.

Is their a software utility you can run for Dell PCs which shows information like the CPU temperature and fan speeds?

charred_water · Post by **charred_water** » Thu Aug 02, 2007 8:51 am

BillyBuerger wrote:I've had some old Dell's over the years myself. I believe the work-around for the "System Fan Failure" message is to turn off something like "keyboard errors" in the BIOS. You'll still get the message but it will just continue on anyways without having to push F1 or anything. If you do a search on the internet for the error message, I'm sure you'll find something more descriptive. But I know it's something related to keyboard errors. (yeah, makes sense.... keyboard.... fan.... same thing)

I hadn't thought to check the BIOS. Thanks for your suggestion!

Das_Saunamies · Post by **Das_Saunamies** » Thu Aug 02, 2007 8:54 am

Yep, check BIOS, disable fan-related warnings and stop-on-errors. And if you need monitoring software, try Speedfan.

charred_water · Post by **charred_water** » Thu Aug 02, 2007 9:01 am

Bluefront wrote:Here's the solution with pictures.....Link. Any three-wire fan should work in this situation with the small wire swap/mod.

"Additional notes: The connector on this fan is not a standardized 3-pin header. However it is wired correctly and will work properly in normal 3-pin headers, as shown in the following image. Owners of Dell PCs should inspect their old fan to be sure it is wired, as shown below from left to right, Black, Red, White. If it is Black, White, and Red instead, you will need to perform a very simple modification to the Red and White pins to swap their places in the housing."

Holy cow. That looks exactly like the NMB fan in my Dell Dimension 8300!

It's great to know I can get an inexpensive replacement if needed.

However, I think I'll try and replace it with a Nexus fan now, assuming the suggestions about the connector work for my systems.

Thanks for all the suggestions. This is a great forum!

charred_water · Post by **charred_water** » Thu Aug 09, 2007 11:39 am

Hey guys,

I just replaced the cpu fans in a Dell 8300 and a Dell Precision 330.

Both cpu fans used the proprietary Dell fan connector. I was unable to pry off the plastic housing. So after checking the color of the wires (black, red, white from left to right), I cut off the Dell fan connector and spliced it to the Antec fans I bought as replacements. (I bought Smartcool fans which change speed depending on the temperature, since these seem to perform the same function as the Dell cpu fans, which also have a thermistor.)

I was then able to plug in the Antec fans into the Dell fan connectors on the motherboards.

When I powered on, the fans seemed to run normally.

However, I am still getting the BIOS warning about "no system fan detected" !!!

If the Dell fan wiring is compatible (power, ground, rpm), can anyone explain why both of my Dell systems continue to warn "no system fan detected" given I am using the Dell fan connector on the motherboard???

Fortunately, the other hint about disabling this warning in the BIOS worked, so I do not have to press F1 in order to boot. I had to change
keyboard check from "report" to "do not report" in the BIOS.

Since I get the "no system fan" warning, I'm a bit worried that the BIOS may be confused. Maybe the BIOS expects a certain RPM from Dell fans?

But if Dell fan connectors are not controlling the cpu fan via the voltage wire. I guess I'm probably okay...

alglove · Post by **alglove** » Thu Aug 09, 2007 4:02 pm

charred_water wrote:Since I get the "no system fan" warning, I'm a bit worried that the BIOS may be confused. Maybe the BIOS expects a certain RPM from Dell fans?

As a matter of fact, "Adjust minimum speed of threshold for system fan detection," was one of the issues addresses in BIOS revision A08.

The current BIOS revision is A09, which also addresses an issue with the fan not starting up when coming out of S3 suspend mode. You can download A09 for the Precision 330 using this link:

Dell Precision 330 BIOS A09

If that link does not work, go to http://support.dell.com and go through the menus.

bonestonne · Post by **bonestonne** » Sat Aug 11, 2007 10:30 am

you could also change settings in the bios to halt on no errors....that would mean the system would start regardless of any issues [although i wouldn't exactly recommend it, as if there is something wrong, you wont know].

johnniecache7 · Post by **johnniecache7** » Sat Sep 08, 2007 7:42 pm

Dell BIOS gives you error if your fan is below 1300rpm they also have non-standard fan headers they sell adapter so you can use any 3-Pin fan you want at Sidewinder Computers.

http://www.sidewindercomputers.com/123excaforde.html