Over the years I have seen quite a few problems with computer fans. Not too long ago I was called to look at a user’s Dell Optiplex GX280 who said his fan was really loud. As soon as I walked in there was no doubt there was a problem since the computer sounded like a jet ready to take off! The CPU fan on this computer is a variable speed fan and only runs as fast as necessary to keep the CPU cool. I ran some diagnostics on the fan. During diagnostics the system tells the fan to run at 3000 RPM and then the fan’s sensor is supposed to report back the speed it is running at. I discovered that this fan had a bad sensor so it was always reporting that it was running at zero RPM even though it was screaming at full speed. I ordered a new fan and that took care of the problem.
Later, however, I was called back because it kept giving the error message “Previous fan failure,” which was accurate since there had been a previous fan failure. I went into the BIOS under “Post Behavior.” I went to “Keyboard Errors” and set it to “Do Not Report” and rebooted the computer. It came up without reporting the “Previous fan failure” error. I returned the setting to “Report” and now the fan error is no longer there. I’d have to say that this was one of the more unique problems with computer fans that I’ve seen.