Computer fan noise and maintenance

[JonathanAnon]

Re: Computer fan noise and maintenance

I have a problem with a computer whose fan stays on 100% of the time, and drives the user mad. I've checked the normal things, cleaned the case etc etc and no dice. I've read that this can happen when the transistor controlling the fan shorts.

It's a 12v 400mA fan, so I was thinking that if solder a 1K linear pot in series with the fan, I could adjust the fan to where it was capable of doing it's job, without driving the user to the insane asylum.

[espresso]

Re: Computer fan noise and maintenance

That pot would have to be powerfull. I use 1W resistors in series with fans to reduce rpm/noise. For 12V/150mA fans the appropriate values would be between 47-100 Ω in my experience. For 400mA you would have to go with even lower values (probably 22-47 Ω).
You should try 100Ω pot (rated at 1.5W at least).

[JonathanAnon]

Re: Computer fan noise and maintenance

Hi Espresso ,

Yeah I was thinking about the wattage across the pot.. If you have it at 1K (fully clockwise) and assume that ~100% of the voltage will be dropped across this, then the current will be 12v/1k = 12mA, and the power will be 12v X 12ma = 12mW ..

As I reduce the resistance across the pot, there will be less of a voltage drop and an increase in current. How is it possible to calculate to make sure that the pot has enough power no matter what position the wiper is in? Do you need to work out the resistance of the load and then calculate for each position of the pot?

[espresso]

Re: Computer fan noise and maintenance

The power of the potentiometer is at its highest when pot's resistance is the same as load. It's my observation, try to verify this.

[mockingbird]

Re: Computer fan noise and maintenance

Does anyone know what I can mix with lubricating grease to thin it out? I have some product or other produced by Loctite that's specially formulated for bearings (but very large bearings at that). I believe it is silicone based with PTFE.

It's pretty viscous, and I think the PTFE also causes it to be stringy, as in like honey when you pull the spoon out, but even moreso than honey. It's not THAT viscous so that I can't use it altogether, in fact it works quite well, but it does slow down the fan some, at least for the first minute.

By the way, don't use all-in-one lubes, they almost ALWAYS have some sort of water displacer in them that't not good for bearings. If you're not sure, read the material safety sheet to see what's in it, if the formula is proprietary, don't use it at all.

[ratdude747]

Re: Computer fan noise and maintenance

Sewing machine oil is pretty thin. As is valve oil for brass instuments... the latter being a more refined oil than the former. At least the singer sewing oil I have in front of me is 100% mineral oil... and iirc the various brass oils I used in middle/high school for my tuba valves was also 100% oil (petroleum distillates).

[999999999]

Re: Computer fan noise and maintenance

I mix Mobil1 synthetic 5W30 motor oil with Mobil1 synthetic grease, mixed in a ratio such that the drop point is barely above room temperature. A side benefit is that due to the resulting neon fushia color of the mix, I know at first glace if I've ever lubed a particular fan.

I would not use a silicone grease because it's not compatible with any remaining petroleum grease the manufacturer used, in addition to having to buy silicone oil to thin it instead of using the grease and oil I already used for my vehicles and other equipment.

[momaka]

Re: Computer fan noise and maintenance

I've never had problem with regular motor oil. Most "worn out" sleeve bearing fans will require a re-lube in a 2 to 3 years (depending on usage... possibly more if not used much) so I don't bother with anything fancy.

My crappy fans even get used motor oil. Never had a problem with that either. Except maybe smelling funny... like a car engine .

[shovenose]

Re: Computer fan noise and maintenance

Hey, a drop of water can do wonders for a fan, for a short period of time! But at work when re-lubing cheapo sleeve bearing fans that I want to last more than a week, a drop of machine oil that doesn't even have a brand name in it, is my preferred solution.

[mockingbird]

Re: Computer fan noise and maintenance

Sewing machine oil is pretty thin. As is valve oil for brass instuments... the latter being a more refined oil than the former. At least the singer sewing oil I have in front of me is 100% mineral oil... and iirc the various brass oils I used in middle/high school for my tuba valves was also 100% oil (petroleum distillates).

But how does that stuff react with the PTFE grease?

I would not use a silicone grease because it's not compatible with any remaining petroleum grease the manufacturer used, in addition to having to buy silicone oil to thin it instead of using the grease and oil I already used for my vehicles and other equipment.

I thoroughly clean the fans like someone instructed in a post on this forum. Remove sticker, remove plug if present, remove spring clip and o-ring, pull out and cleane verything with acetone nail polish remover.

[999999999]

Re: Computer fan noise and maintenance

^ That's not going to get the petroleum oil out of the sintered brass bearing, which is ideally supposed to absorb some of the lube.

It probably is better to clean everything off but I've never found it necessary. In theory it may wear faster if not cleaned but in practice it seems like the wear rate doesn't matter much so long as there is sufficient lubricant present.

The PTFE in the grease isn't important but that it is silicone based means you should use silicone oil to thin it, not sewing machine or any other type of petroleum or mineral oil. What you are talking about is probably meant for races in ball bearings, not lubing sleeve bearings. A lot of silicone oil is thick enough by itself if not too thick, and wouldn't need mixed with grease.

[mockingbird]

Re: Computer fan noise and maintenance

Interesting, I wasn't aware of that. I clean them because whatever the Chinese manufacturers put in there turns brown and nasty after some time.

Silicone oil sounds like a great idea. Thanks.

Regarding ball bearings, I've seen a video on youtube of someone lubing them in pressure chamber with motor oil. Great idea if you have a pressure chamber. Anyone know where to buy fan replacement ball bearings?

[999999999]

Re: Computer fan noise and maintenance

^ It might have started out brown and nasty, some cheaper moly greases look like that.

Years ago I looked for fan sized ball bearings and it turned out that they cost more for a pair than a whole new dual ball bearing fan. Granted, fans were cheaper then too, but you can get major brand dual ball bearing fans from electronic surplus 'sites for about $4 each while places like McMaster-Carr want around $6 ea. bearing.

[ron350]

Re: Computer fan noise and maintenance

Ok I am new here and just passing on what I have been taught about sintered bearings many years ago.

From what I have seen these small fans with OUT ball bearings use Oilite bearings.
http://en.wikipedia.org/wiki/Oilite

I have been using Zoom Spout Turbine oil to lube these Oilite bearings.
This oil usually can be found on the counter of most HVAC or refrigeration supply stores.

Oilite bearings are supposed to be surrounded by felt or some kind of wicking material saturated with oil.
When an Oilite bearing wears out or is made out of spec, like many refrigerator evaporator fans, they start to rattle and usually must be replaced. If I can remove the bearing I soak it in turbine oil over night. If the bearing can’t be removed I twist a piece of paper towel and push it into the bearing and soak it with oil and let it soak in.
If a fan or motor still rattles after lubing with turbine oil I have had some luck with Tal-5 PTFE oil even though the PTFE particles probably clog the pores in the bearing.

[momaka]

Re: Computer fan noise and maintenance

It probably is better to clean everything off but I've never found it necessary.

For fans that have seized or become nearly seized, you have to take them fully appart and clean everything. Otherwise, they will seize again.
I had this happen to both a 92 mm and 120 mm fans when I rushed the cleaning on them (i.e. didn't do the sleeve bearing "scratching" parallel to the shaft direction.) The 120 mm fan worked for about half a year for maybe 1 to 2 hours a day, about 4 days a week. Then it started to rattle again. Cleaned it again much more thoroughly the second time, and now it's been 1 year with much more uptime, and still no problem. The 92 mm fan I didn't even use! Just cleaned and oiled, then let it sit for about a year. After I came back to it, there was still oil in the shaft, but the fan did not spin as freely as when I cleaned it. Did a second through cleaning and lubing. The last time I took it out and used it, it's been sitting for 2 years after that second cleaning. But now it spins normally.

So yeah, cleaning the sleeve bearing well is the most important thing! What oil/lubricant you use... not so much as long as it isn't too viscous or doesn't dry with time. The 120 mm fan I was talking about above I used used motor oil on it.

[espresso]

Re: Computer fan noise and maintenance

It's pretty viscous, and I think the PTFE also causes it to be stringy, as in like honey when you pull the spoon out, but even moreso than honey..

That's not because of ptfe, the grease has tackifier agent added that increases stringiness. I used that kind of viscous lube to grease 12cm sleeve bearing fan.
Silicone oil is a poor lubricant, I have it here and it can't form a film that's thick enough, like mineral or synthetic oil. I wouldn't use it for fans. Actually if you try to use only silicone oil to lubricate bearings, you would still hear silent rattling sound sometimes - meaning poor lubrication.
I'd also stay away from mixing oil with grease to avoid incompatibilities.

[999999999]

Re: Computer fan noise and maintenance

For fans that have seized or become nearly seized, you have to take them fully appart and clean everything. Otherwise, they will seize again.
I had this happen to both a 92 mm and 120 mm fans when I rushed the cleaning on them (i.e. didn't do the sleeve bearing "scratching" parallel to the shaft direction.) The 120 mm fan worked for about half a year for maybe 1 to 2 hours a day, about 4 days a week. Then it started to rattle again. Cleaned it again much more thoroughly the second time, and now it's been 1 year with much more uptime, and still no problem. The 92 mm fan I didn't even use! Just cleaned and oiled, then let it sit for about a year. After I came back to it, there was still oil in the shaft, but the fan did not spin as freely as when I cleaned it. Did a second through cleaning and lubing. The last time I took it out and used it, it's been sitting for 2 years after that second cleaning. But now it spins normally.

So yeah, cleaning the sleeve bearing well is the most important thing! What oil/lubricant you use... not so much as long as it isn't too viscous or doesn't dry with time. The 120 mm fan I was talking about above I used used motor oil on it.

I can only tell you what has worked for me. No cleaning, thicker lube, and a lot of it, not just a drop or two but rather packing the area full of it. Maybe over time this flushes the debris out.

A thicker lube will stay put better instead of leaking out the other end of the worn bearing, and the thicker film strength makes up for the greater bearing gap and reduces wobble.

I can't tell you how many years they would last like this because if a fan is bad enough to have seized I consider it a one lube candidate then it gets replaced within about year rather than relubed a 2nd time. None have seized within that year. An exception is tiny high RPM video card fans, I wouldn't trust one of those which seized and then was relubed for more than a month.

However I should mention prevention. These days I don't run any systems with sleeve bearing fans in them unless I had already lubed the fan before it started showing signs of needing it. I literally lube brand new fans before putting them in a system.

[momaka]

Re: Computer fan noise and maintenance

No cleaning, thicker lube, and a lot of it, not just a drop or two but rather packing the area full of it. Maybe over time this flushes the debris out.

Well, I am kind of cheap like the Chinese, so I rather not put more lubricant than is needed . So that's why I go the extra mile with the cleaning. Also, for fans that were badly stuck, they tend to make circular wear grooves in the sleeve bearing. This, in my experience, causes considerable performace loss in terms of RPM and is what often makes the fan seize again.

A thicker lube will stay put better instead of leaking out the other end of the worn bearing, and the thicker film strength makes up for the greater bearing gap and reduces wobble.

Again, that's what my cleaning takes care of so that I can use any lube. After cleaning the fan, I take a small sharp screw driver and literally put scratches on all sides inside the sleeve bearing, parallel to the fan shaft. Then clean again and lube. The scratches act as reservoirs for the oil and this allows the fan to hold its oil a lot longer. I guess you can say this is similar to car engine rebulding (except there, you polish the inside of the engine in exactly the opposite direction, making circular grooves that are perpendicular to the piston direction of travel).

An exception is tiny high RPM video card fans, I wouldn't trust one of those which seized and then was relubed for more than a month.

I have 3 that are several years old now. All were grouwling badly when I found them. One was actually nearly seized. Again, just good cleaning takes care of them. The nice thing about small fans is that they are light, so even if they seize, their sleeve bearing can never wear down too much. With big fans (especially ones positioned vertically), you can get quite a bit of wear.

I literally lube brand new fans before putting them in a system.

Same here, if I don't like how they sound. It's been a while since I bought new fans, though. Most of the time, it's refurb the old one and use again.

[999999999]

Re: Computer fan noise and maintenance

^ Cleaning does not reduce wobble. Once the bearing is worn that shape the only thing that will help is a new bearing or thicker lube. It may reduce further wear in an elongated shape, but so does using a thicker lube and plenty of it.

It seems we have alternate methods but that both work for the durations we need them to, that I simply don't need the fans to last as long.

I am not very concerned about the amount of lube because having to buy the grease and oil anyway for vehicles and other equipment, the small amount left in a grease tube that my grease gun can't get out is a lifetime's supply of grease for fans, and similarly with the oil, what is left dripping out of a jug after an oil change is plenty.

[goodpsusearch]

Re: Computer fan noise and maintenance

What do you think about treadmill oil?

I think it is silicone oil. Is it suitable for fans?