CPU Fans - Which, when, and why

[ChaosLegionnaire]

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!

[momaka]

Re: CPU Fans - Which, when, and why

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.

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.

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...

[socketa]

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).

[socketa]

Re: CPU Fans - Which, when, and why

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

[stj]

Re: CPU Fans - Which, when, and why

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

[socketa]

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?

[stj]

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.

[socketa]

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

[stj]

Re: CPU Fans - Which, when, and why

then they had 2 designs

[socketa]

Re: CPU Fans - Which, when, and why

that's still an SMD component on that photo

[stj]

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?

[socketa]

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

[stj]

Re: CPU Fans - Which, when, and why

i dont think that fault is caused by the missing part

[redwire]

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?

[stj]

Re: CPU Fans - Which, when, and why

isnt yellow the tach?

[redwire]

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.