CPU Fans - Which, when, and why

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  • ChaosLegionnaire
    HC Overclocker
    • Jul 2012
    • 3264
    • Singapore

    #21
    Re: CPU Fans - Which, when, and why

    what the?! u dont lube ball bearing fans! it just makes the ball bearing ring slippery and not grip on the shaft of the rotor causing grinding noises. u only lube sleeve bearings!

    anyway, that second twitchy fan definitely has a bad motor phase on one of the coils so the fan is considered bad unless u can repair the faulty phase like momaka said.

    as for that slow pulsing fan, clean off all the oil off the ball bearing ring and shaft with a paper towel. lol! those arent meant to be lubed with oil!

    Comment

    • momaka
      master hoarder
      • May 2008
      • 12170
      • Bulgaria

      #22
      Re: CPU Fans - Which, when, and why

      Originally posted by socketa
      Yes, they are dual ball bearing fans
      One of them had dust bunnies inside, and i gave both of them an oil with hair clippers oil
      After giving them a spin by hand, they sound more noisey now!, so it does sound like (at least) a bearing issue.
      Yup, that's normal for any ball bearing fan.
      BBs don't do well with oil. They'll get even more noisy than before, even if the shaft doesn't slip in the bearing from the oil. I don't know why, but it's just their nature. When BBs fail or get worn, they can't be fixed. However, if you really are in a pinch to get a seized or hardly-turning BB going, then you can open them by removing their protective shield on both sides (there is a thin spring c-clip along the outer edge of the bearing holding the side shields.) Once removed, the shield will come off easily. With both sides off, spray the bearing with brake cleaner and wipe well with paper. Then you can drop some oil or grease in the bearing with a needle. After this, the bearing should turn freely.

      I don't suggest using repaired BBs for long, if at all. Once a BB has failed, it's just time to replace it.

      For this reason, I bought a bag of cheap bearings from China as an experiment (10x bearings for $1 shipped). Quality is dubious on all of the bearings, of course, and about half of the ones I got were just as noisy as the failed bearings they were meant to replace. But the other half that weren't, I was able to use and fix a few fans. Not really a worthwhile endeavor. More of a curiosity if that would fix my fans and because I like saving things from getting trashed. So far so good with the few fans I fixed, though they haven't seen that much use.

      Originally posted by socketa
      Plugging them into 12V supply: one fan spins slowly and pulsing (about every 2 seconds) and has a rumbling feel to it.
      That one definitely sounds like a failed bearing.

      Originally posted by socketa
      The other fan just twitches and will do a revolution if i turn the fan to either two of the four (opposite) positions, that the fan can rest at. If it lands back on one of those positions it will go again, untill it lands on either of the other two positions, where it will just twitch.
      That one either has a bad (open) winding somewhere or, more likely, bad winding driver transistors/IC. If windings are good, replacement driver transistors/IC may bring the fan back to working order. Not really worth it. But if you are curious...

      Comment

      • socketa
        Asbelowsoabove
        • Jun 2014
        • 660
        • samsara

        #23
        Re: CPU Fans - Which, when, and why

        i wiped all of the oil off of the bearings and shaft, then swapped the bearings, spring, c-clip. and fan of the twitcher into the one that was going slow. Spins really nicely by hand (no rumbling, or hissing sounds of friction), but when powered by a molex connector, it still goes slow (or just twitches when plugged into the board).
        Last edited by socketa; 12-14-2019, 03:06 AM.

        Comment

        • socketa
          Asbelowsoabove
          • Jun 2014
          • 660
          • samsara

          #24
          Re: CPU Fans - Which, when, and why

          Can anyone say if the missing component on this fan would likely be a NTC thermistor?
          Attached Files

          Comment

          • stj
            Great Sage 齊天大聖
            • Dec 2009
            • 30963
            • Albion

            #25
            Re: CPU Fans - Which, when, and why

            it's very small, whatever it is - a thermocouple?
            https://www.amazon.com/Delta-AFB0712.../dp/B00U6V9S0Q

            Comment

            • socketa
              Asbelowsoabove
              • Jun 2014
              • 660
              • samsara

              #26
              Re: CPU Fans - Which, when, and why

              i measured one on a similar fan, and heated it up a bit with a hair dryer - the resistance went down as the temp went up
              7k to 4.6k
              it's a black SMD
              lots of photos that look like that come up when searching for smd NTC thermistor, but none came up for thermocouple
              looks like it's temperature related because of the gap in the board
              10k NTC thermistor?

              Comment

              • stj
                Great Sage 齊天大聖
                • Dec 2009
                • 30963
                • Albion

                #27
                Re: CPU Fans - Which, when, and why

                it's not SMD - look close at that photo
                it's a wire-ended bead mounted off the board to get the airflow - probably how it got knocked off.

                Comment

                • socketa
                  Asbelowsoabove
                  • Jun 2014
                  • 660
                  • samsara

                  #28
                  Re: CPU Fans - Which, when, and why

                  here's a better photo of the same model fan
                  https://www.elecok.com/media/catalog..._tmp_img_2.jpg
                  that's an SMD component, and it's not mounted off of the board,
                  the split in the board exposes the black rectangular body to the air
                  Last edited by socketa; 08-18-2022, 12:03 AM.

                  Comment

                  • stj
                    Great Sage 齊天大聖
                    • Dec 2009
                    • 30963
                    • Albion

                    #29
                    Re: CPU Fans - Which, when, and why

                    then they had 2 designs

                    Comment

                    • socketa
                      Asbelowsoabove
                      • Jun 2014
                      • 660
                      • samsara

                      #30
                      Re: CPU Fans - Which, when, and why

                      that's still an SMD component on that photo

                      Comment

                      • stj
                        Great Sage 齊天大聖
                        • Dec 2009
                        • 30963
                        • Albion

                        #31
                        Re: CPU Fans - Which, when, and why

                        i linked the wring photo, i had one with an axial wire-ended bead on it.
                        what does it do if you already have a pwm wire though???
                        which takes priority, the pwm or the sensor?

                        Comment

                        • socketa
                          Asbelowsoabove
                          • Jun 2014
                          • 660
                          • samsara

                          #32
                          Re: CPU Fans - Which, when, and why

                          when i plug the connector into the board, and start it up, the fan spins
                          at first, the speed seems to vary a bit, but it's close to normal
                          i get "'CPU fan warning" message after booting
                          shows zero RPM for CPU fan in the BIOS

                          Comment

                          • stj
                            Great Sage 齊天大聖
                            • Dec 2009
                            • 30963
                            • Albion

                            #33
                            Re: CPU Fans - Which, when, and why

                            i dont think that fault is caused by the missing part

                            Comment

                            • redwire
                              Badcaps Legend
                              • Dec 2010
                              • 3900
                              • Canada

                              #34
                              Re: CPU Fans - Which, when, and why

                              Zero RPM means the tachometer output (blue wire) is not working, the connector pinout matches the M/B?

                              Comment

                              • stj
                                Great Sage 齊天大聖
                                • Dec 2009
                                • 30963
                                • Albion

                                #35
                                Re: CPU Fans - Which, when, and why

                                isnt yellow the tach?

                                Comment

                                • redwire
                                  Badcaps Legend
                                  • Dec 2010
                                  • 3900
                                  • Canada

                                  #36
                                  Re: CPU Fans - Which, when, and why

                                  The 4-pin PC fan standard has pin 3 as Tach, pin 4 as PWM.
                                  But the Delta AFB0712VHB fan pics has pin 3 as blue.
                                  Attached Files

                                  Comment

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