CPU Fan Not Detected

Desktop

Desktop
Desktop computer Forums (Audio, General Hardware, Video)

CPU Fan Not Detected

This question is answered

This is in reference to a Dell Dimension 2350 desktop PC with XP Home SP3.  Recently I began getting a POST error stating the CPU fan was not detected, Press F1 to continue or F2 to enter setup.  Pressing F1 continues Windows start-up normally, and the PC runs A-OK.  I checked the fan for any indication of a problem, and all appears to be normal.  The CPU heatsink is clean, the fan runs normally, and there is not an overheating issue.  Given these symptoms, is this likely a motherboard failure with the fan control...and/or is there a workaround?  Thanks.

Verified Answer
  • OK, for anyone interested, I finally resolved the "CPU Fan Not Detected" issue described in this thread.  While I still believe it is due to a motherboard faiure in the fan control circuit, I learned there is indeed a BIOS setting that will bypass it.  I must have been in the BIOS a dozen times and did not recognize it.  Under the POWER tab, there is a setting for ACPI Suspend Type.  Changing it from S3 to S1...and....saving the changes as Custom Defaults under the Exit tab resolved the issue.  I had tried the S1 setting earlier, but just exited with F10.  Apparently that was not enough, and the changes had to be saved as Custom Settings.

    Thanks again to all who responded to my inquiry.

    Ron

All Replies
  • RonM1962

    First check the fan power connector to the motherboard, by removing and reconnecting.

    Then try this and see if it makes a difference.

    Start the system.

    Press 'F2' to enter System Setup.

    Highlight 'System Event Log' and press the 'Enter' key.

    Highlight 'Clear System Event Log' and press the 'Enter' key.

    Press the 'Esc' key twice to restart.

    Bev.

     

    If my answer was helpful, please use the 'Did this answer the question' and click: Yes
    Forum Member since 2001
    I am not employed by Dell

  • Thanks, Bev.  Tried all that...no change.  Still get the "alert" at POST.  Curious if there is a way to disable or bypass the alert?  Nothing in the BIOS to address.

    Ron

  • RonM1962

    Thanks, Bev.  Tried all that...no change.  Still get the "alert" at POST.  Curious if there is a way to disable or bypass the alert?  Nothing in the BIOS to address.

    Ron

    The BIOS uses the fan's RPM to determine its existence and health ... perhaps the fan is no longer signaling that?

    I replaced the worn-out factory fan in my 2350 with a Vantec bought from Newegg.

  • Thanks RDUNNILL.  Good point.  I have tried a new fan and get the same results.  I was hoping there might be a way to bypass the alert since it is a false alert.  There is no way in the BIOS to do that, so wondering if it would be possible to "jumper" something on the motherboard to bypass or ignore the check.  It's an old PC, but works fine other than the nagging alert at POST.

     

  • RonM1962

    As you have replaced the fan, hopefully with a compatible unit, it would seem that you need to replace the motherboard, to stop the nag.

    Had the same problem with a 8400, tried everything to stop the nag appearing on start up, but found that replacing the motherboard was the answer.

    Bev.

     

    If my answer was helpful, please use the 'Did this answer the question' and click: Yes
    Forum Member since 2001
    I am not employed by Dell

  • Bev, again, thanks for the response.  I have tried everything, even jumpering the fan power connector as suggested in another forum, but nothing stops it.  

    So, guess i will look for a motherboard replacement.

    Thanks..Ron

  • Ron.

    When you replaced the fan, was a Dell OEM unit installed?

    Yep, it bugged the heck out of me, having replace a working motherboard because of a stupid nag.

    Bev.

     

     

    If my answer was helpful, please use the 'Did this answer the question' and click: Yes
    Forum Member since 2001
    I am not employed by Dell

  • I used one of these in my 2350. It has the third conductor for RPM.

  • Bev and rdunnill,

    The fan I used for a replacement is not a Dell fan, although it does have three wires (one for RPMs) and it seems to work OK.  Maybe I'll try a Dell OEM fan before I replace the motherboard.  Will let you know result.  Thanks.

  • Ron.

    Before replacing the motherboard, that's what I would do, when a non-compatible fan installed, the same error message is shown on startup.

    Bev.

     

    If my answer was helpful, please use the 'Did this answer the question' and click: Yes
    Forum Member since 2001
    I am not employed by Dell

  • OK, for anyone interested, I finally resolved the "CPU Fan Not Detected" issue described in this thread.  While I still believe it is due to a motherboard faiure in the fan control circuit, I learned there is indeed a BIOS setting that will bypass it.  I must have been in the BIOS a dozen times and did not recognize it.  Under the POWER tab, there is a setting for ACPI Suspend Type.  Changing it from S3 to S1...and....saving the changes as Custom Defaults under the Exit tab resolved the issue.  I had tried the S1 setting earlier, but just exited with F10.  Apparently that was not enough, and the changes had to be saved as Custom Settings.

    Thanks again to all who responded to my inquiry.

    Ron

  • Ron.

    Happy to hear the problem is resolved and thank you for posting the solution.

    Bev.

     

    If my answer was helpful, please use the 'Did this answer the question' and click: Yes
    Forum Member since 2001
    I am not employed by Dell

  • THANK YOU, RON!  I'm going to try this tomorrow.  All along, I thought it was because I didn't replace it with the exact same model fan.  I'm going to give this a whirl tomorrow. 

    Thanks again for posting!!!!  I know often times many forget to post once they've figured things out.  Have a good one!

    - Elizabeth (Reboot IT Now)

  • I actually found a flawless work around, It's not pretty but worked first time. I had another dell fan that worked but didn't turn the RPM deficit error, i.e. "CPU fan not found". I took a small AMD processor (three lead) fan that did turn the alarm off, Spliced the red and black lead accordingly from my dell fan and both fans turn, but the sensor from the amd is turning the right RPM signal.