Question Fans not being recognized

Jan 20, 2022
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I plugged the included fans of my case (nzxt phantom 820) into my motherboard (Asus x99-a) And they aren't being recognized in bios. The only fan that is being recognized is the CPU fan. The fans spin when I turn the pc on, but they all turn off when I windows is opened. Please help.
 
I plugged the included fans of my case (nzxt phantom 820) into my motherboard (Asus x99-a) And they aren't being recognized in bios. The only fan that is being recognized is the CPU fan. The fans spin when I turn the pc on, but they all turn off when I windows is opened. Please help.
Do you have the fan ports on in the bios? That's a odd issue to have never heard of this issue unless plugged in wrong, are they 3 or 4 pin fans?
 
Jan 20, 2022
11
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10
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Do you have the fan ports on in the bios? That's a odd issue to have never heard of this issue unless plugged in wrong, are they 3 or 4 pin fans?
Yes. I do see the fan ports in bios, but they just say N/A. I have 3 pin fans. I think they are plugged in right, because they start spinning when I start up the pc. And when windows starts, they stop.

They do keep spinning while in bios tho. But it just doesn't recognize them.
 

Paperdoc

Polypheme
Ambassador
First thing to check may be WHEN the fans do and do not run. You believe they stop when Windows loads. The NORMAL operation is this. Immediately at start-up all the fans should start at full speed. In a few seconds as the POST process completes they should then reduce their speed to whatever slow speed is needed to cool a system that is already cold - that is the minimum speed the mobo BIOS calls for. Now, MAYBE that timing of them stalling just happens to be roughly when the POST process completes and Windows starts to load.

Next some details. Any 3-pin fan CAN be plugged into the 4-pin headers your mobo has, and there is only one way to do this because of the plastic "tongue" sticking up beside the pins of the header - that fits between two ridges down the side of the female fan connector. So check, but I expect that is not an issue. Now, your mobo has several fan headers, and only FOUR of them called CHA_FAN1 through 4 are to be used for case ventilation fans. So check whether those are the headers you are using for these fans.

Assuming all those items are OK, I think I know why you are getting this issue, and how to fix. What may be happening is that the pre-set fan control system is telling those fans to run too slowly so they stall after the initial full-speed start-up. When that happens, each header suddenly receives NO speed signal from its fan, so it shows that fan a "N/A" as it it does not exist at all. So we'll start with a test to verify. See your mobo manual, p. 3-7. Note that the default Profile setting along the bottom is "Standard", and that will use the "Fan Curve" above that to decide what speed to run each fan according to temperature measured at a mobo sensor. At start-up that temp is low, so the fans are told to run at the specified minimum speed, and that MAY be too slow so they stall. So, for EACH of the four CHA_FAN headers you are using for these fans, chose instead the "Full Speed" option to the right. While you are there, for each header also check that, at top right, it is set to DC Mode, (not PWM) that is required for 3-pin fans. When you've set all 4, use Esc to get back to Main Menu, then F10 to get to the Exit Menu (p. 3-60). There choose Save Changes and Reset to save your new settings and reboot. If everything is working OK, all those fans should rest-start at full speed and stay that way That would prove that the fans and headers work as long as they are configured correctly.

Assuming that worked, now for the fix. Go back into BIOS Setup (manual p. 3-7). For ONE of the CHA-FAN headers, first change it to Standard Profile and NOTE the speed it is using for the lowest one or two temperatures. Now change to the Profile item "Manual" at the far right. Now you can use your mouse to change the points on the "Fan Curve" by dragging them. For the two lowest temperatures, drag the speed value upwards to a new minimum speed. Again go through the Exit Menu to save and reboot, and check your fans. The ONE fan you just changed should start at full speed, then slow down to a min speed but NOT stall. The others should stay at fixed full speed. You can repeat this, trying different minimum speed settings, until you identify the right min speed so the fan does not stall. Then go back in and make that same setting for ALL of the CHA_FAN headers, and all your fans should work properly.

Let us know what happens.
 
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Jan 20, 2022
11
0
10
0
First thing to check may be WHEN the fans do and do not run. You believe they stop when Windows loads. The NORMAL operation is this. Immediately at start-up all the fans should start at full speed. In a few seconds as the POST process completes they should then reduce their speed to whatever slow speed is needed to cool a system that is already cold - that is the minimum speed the mobo BIOS calls for. Now, MAYBE that timing of them stalling just happens to be roughly when the POST process completes and Windows starts to load.

Next some details. Any 3-pin fan CAN be plugged into the 4-pin headers your mobo has, and there is only one way to do this because of the plastic "tongue" sticking up beside the pins of the header - that fits between two ridges down the side of the female fan connector. So check, but I expect that is not an issue. Now, your mobo has several fan headers, and only FOUR of them called CHA_FAN1 through 4 are to be used for case ventilation fans. So check whether those are the headers you are using for these fans.

Assuming all those items are OK, I think I know why you are getting this issue, and how to fix. What may be happening is that the pre-set fan control system is telling those fans to run too slowly so they stall after the initial full-speed start-up. When that happens, each header suddenly receives NO speed signal from its fan, so it shows that fan a "N/A" as it it does not exist at all. So we'll start with a test to verify. See your mobo manual, p. 3-7. Note that the default Profile setting along the bottom is "Standard", and that will use the "Fan Curve" above that to decide what speed to run each fan according to temperature measured at a mobo sensor. At start-up that temp is low, so the fans are told to run at the specified minimum speed, and that MAY be too slow so they stall. So, for EACH of the four CHA_FAN headers you are using for these fans, chose instead the "Full Speed" option to the right. While you are there, for each header also check that, at top right, it is set to DC Mode, (not PWM) that is required for 3-pin fans. When you've set all 4, use Esc to get back to Main Menu, then F10 to get to the Exit Menu (p. 3-60). There choose Save Changes and Reset to save your new settings and reboot. If everything is working OK, all those fans should rest-start at full speed and stay that way That would prove that the fans and headers work as long as they are configured correctly.

Assuming that worked, now for the fix. Go back into BIOS Setup (manual p. 3-7). For ONE of the CHA-FAN headers, first change it to Standard Profile and NOTE the speed it is using for the lowest one or two temperatures. Now change to the Profile item "Manual" at the far right. Now you can use your mouse to change the points on the "Fan Curve" by dragging them. For the two lowest temperatures, drag the speed value upwards to a new minimum speed. Again go through the Exit Menu to save and reboot, and check your fans. The ONE fan you just changed should start at full speed, then slow down to a min speed but NOT stall. The others should stay at fixed full speed. You can repeat this, trying different minimum speed settings, until you identify the right min speed so the fan does not stall. Then go back in and make that same setting for ALL of the CHA_FAN headers, and all your fans should work properly.

Let us know what happens.
Thank you so much! It worked! I've been trying to fix this for weeks now, I have been using one of those fan hubs, so they've been running full power and have been really loud.

Also, could you maybe help with one more problem I've been having?
Here's the link to the thread: https://forums.tomshardware.com/threads/fan-not-spinning.3745901/#post-22585990
One of my CPU fans isn't spinning, I've tried everything i could find online, but it's still not spinning, maybe you might know something (or it could've just broken when I touched it)
Please help when you have some spare time!

Heres a list of everything ive tried:
Spinning the fan as fast as i could to "jump start" the fan
Using canned air (I actually just used a hair dryer, and set it to cold air) And jump start it that way.
Using a different pin on the mobo

The fan doesn't even spin at all when i start the pc. It just sits there doing nothing.
 
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