CPU fan pulses as soon as computer is turned on.

[Teesh1]

CPU fan pulses as soon as computer is turned on, so it doesn't seem to be a heat related issue.  Have gone into BIOS and watched the speed pulse, but am not able to adjust or change fan mode.  Checking for updates using HP Assistant, there are none, so I assume the BIOS is up to date.  This problem started when we turned the computer off overnight for the first time in a long time, due to a predicted weather event.  We've run MalwareBytes and done an Avast scan.  We've also run HP Assistant fixes and diagnostics.  We've replaced the CPU fan with the same make and model as the original with no change.  Does anyone have an idea what we should try next?  The computer is a Pavilion Desktop 570-p049 new in 2018 and purchased directly from HP.

[old_geekster]

@Teesh1 , welcome to the Community.

You state that you turned the computer off because of a weather event.  Did you actually disconnect the computer from the power source or leave it plugged-in?  If there was lightening it could have been damaged if it were still plugged-in.

[Teesh1]

The weather event was an anticipated power outage, not lightning.  For what it’s worth, the computer is plugged into an APC battery with surge protection and we also have a whole house surge protector in the main panel.  Thanks anyway.  We appreciate any further suggestions. 

[DGroves]

some fans will do this normally if the temp sensor is saying that the fan does not need to be on

some fans also contain a built-in temp sensor, so make sure to replace the fan with the exact model number

the fan has most likely failed/is failing  look at the fan and you should see the fan model number printed on a label

google this number for a replacement fan

[Teesh1]

If you reread my original post, you’ll see we did install a new fan of the same make and model.  As the problem starts as soon as we turn on the computer, it’s not a temperature issue.  Thank anyway. Any other suggestions?

[old_geekster]

Thank you for the additional information, @Teesh1!

Just for clarification, is it the fan attached to the processor or the case fan that is surging?

[Teesh1]

It’s the fan attached to the processor.

[DGroves]

run a cpu testing program that loads the cpu to 100% usage this will increase the cpu temp

does the fan turn on during the cpu test? does the cpu fan speed increase during the test? if so then the cpu temp at idle is most very low (check the bios temp or use 3rd party software) and just the heatsink will keep the temps in check so the fan will not run or may pulse