HP Z840 Worksration fan assembly run full speed


I have a HP Z840 Workstation.

From time to time fans assembly will run on full speed that until I will open the chassis door and then the fans speed will go to normal again. 

Any Idea what cause this issue and how to fix this problem?


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  • Can't you tweak the fan settings in the BIOS?

      • Oded
      • Oded
      • 1 yr ago
      • Reported - view

      Hi thanks for the reply.

      I don’t think it’s anything to do with the bios.

      I think it’s got to do with the connection of the assembly to the motherboard.

      When you take the assembly out and when you put it back in you can’t really see if the power seats correctly it’s under the assembly.

      I placed the assembly In.

      I left the side open.

      I placed the machine on its side and slam gently against the floor the assembly start running fast I tap on the assembly and repeat the process again.

      Tap few time on the assembly and it’s stop from running fast and it doesn’t happen anymore.

      This is the downfall of this machine all this fans with only one connection.

      I will update If the assembly will start running fast again.

  • Hi everyone

    I would to share with you the solution for my fan problem.

    I tried many things and search in many forums and things just got worse  CPU fan just kept going fast speed all the time.

    I even set BIOS back to default 2.54 but nothing helped.

    Until I came across similar problem at HP support forum.

    Unplug power core remove CMOS battery wait 10 minutes install battery again fix time and date in BIOS.

    After installing back the battery everything back to normal so far no problems very happy.

    Here is the link:




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