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CPU Fan Not Detected
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.
RonM1962
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June 13th, 2010 19:00
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
shesagordie
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June 9th, 2010 14:00
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.
RonM1962
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June 9th, 2010 18:00
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
rdunnill
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June 9th, 2010 18:00
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.
RonM1962
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June 10th, 2010 07:00
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.
shesagordie
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June 10th, 2010 11:00
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.
RonM1962
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June 10th, 2010 19:00
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
shesagordie
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June 10th, 2010 20:00
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.
rdunnill
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June 10th, 2010 22:00
I used one of these in my 2350. It has the third conductor for RPM.
RonM1962
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June 11th, 2010 10:00
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.
shesagordie
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June 11th, 2010 10:00
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.
shesagordie
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June 13th, 2010 20:00
Ron.
Happy to hear the problem is resolved and thank you for posting the solution.
Bev.
RebootITNow
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October 26th, 2011 20:00
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)
car-free
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January 26th, 2012 07:00
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.