CPU Fan going from max RPM to 0

[Brian Brooks]

I have been having an issue for the past few days where my CPU Fan spins mostly at 2800 RPM then will sometimes drop as low as 0 for a couple seconds then back up to 2800.. Immediately when I turn on my PC it spins to 2800 RPM..I have a Scythe Ninja 3 fan and Asus P8Z68-V Pro motherboard.. Could this be anything software related or is the fan about to die?
I also noticed that Fan Xpert in AI Suite is registering my Fan RPMS at ~2800 with 20% fan power all the way up to 100%. 2800 RPM for all power levels & the index temps in HW Monitor are showing some unusually high readings that appear to be false.


https://www.dropbox.com/s/dw0df06dtdhd3rh/fan.png?dl=0

OS Version: Microsoft Windows 7 Ultimate, Service Pack 1, 64 bit Processor: Intel® Core™ i5-2500K CPU @ 3.30GHz, Intel64 Family 6 Model 42 Stepping 7 Processor Count: 4 RAM: 8167 Mb Graphics Card: NVIDIA GeForce GTX 570, 1280 Mb Hard Drives: C: Total - 114370 MB, Free - 42412 MB; D: Total - 238472 MB, Free - 37756 MB; E: Total - 476936 MB, Free - 31589 MB; Motherboard: ASUSTeK Computer INC., P8Z68-V PRO GEN3 Antivirus: Avira Antivirus, Updated and Enabled

 

[Darkbreeze]

Try connecting another fan to the CPU fan header and see if it does the same thing. Also, try connecting the CPU fan to a case fan header and see if the fan displays the same behavior. If a different fan does the same thing on the CPU fan header, then the problem is probably bios or board controller related.

If the CPU fan does it on another fan header, then it's something with the PWM or voltage control circuit on the fan.