Rebuilding A Fried Fan Motor

The fan motor on [Pete’s] oscillating tower fan conked out on him. It’s a shame to throw away the whole thing, but it’s near impossible to source parts for a small appliance like this one. So he set out to rebuilt the motor and get the thing working like new.

The motor in question is of the brushless AC variety. [Pete’s] gut told him that the failure was due to bad lubrication of the bearings at the factory. It stopped working because the commutator could no longer rotate freely. A check of the continuity of each of the coils led him to this thermal fuse. When the motor seized the AC current built up a lot of heat. This fuse is made to burn out before a fire can start but now it needs to be replaced. With a new one in place he reassembled the motor, making sure to pack the bearings with some quality lubricant. Now he’s once again ready for a long hot summer.

53 thoughts on “Rebuilding A Fried Fan Motor

  1. Amazes me how motors mix up otherwise smart engineer types.
    Not “brushless ac” just capacitor run by the look of it. Though there are no brushes, this is just a standard cheap AC induction motor.

    No commutators on these guys, just the squirrel cage rotor. Commutators are where the brushes ride on DC/universal motors. Lots of copper bars.

    Rebuild? Maybe you could call it that. I was hoping to see him rewind it… always fun to see a “civilian” take on my niche trade.

      1. I must agree in part with #1.rectifier in the message although not in the form to express it.

        Instead of educating people to gain knowlege to do things for themselves even if is just replacing a non serviceable fuse, such blatant technical errors, misconceptions of elemental concepts and hype in the entry does just the opposite, confussing people and making it harder to learn properly. That is my guess about what pissed him the most.

        Always is nice to see people willing to understand and fix things..

    1. Agreed. Though truthfully I dumped industrial MRO for biochemistry…I got tired of having to wear t-shirts that read “I’m here because you @&$*ed up.”

      I do not miss repair, rebuilding, or rewinding motors or worse troubleshooting the control circuits because dipthong dumped his Pepsi in the operator panel…

    2. Well of course you are technically correct, congratulations ;) Then again Mike wasn’t exactly wrong either. Yea repair would have been the better verb, but not worth splitting hairs over.

      1. Totally seconded and frankly was hoping for a rewinding tutorial cause I been baffled as to how to redo at least a 2 stage fan let alone a 3 stage unit … fuses and grease are just fussing to me … but still don’t hurt to post this hack either. wording could have been better.
        I hope to see a rewinding tutorial if possible son. :D

    3. Rather than talk down to us civilians, you should do a write up or video on rewinding coils.

      I’m really tired of people telling me I’m doing something wrong then refusing to show me the correct way of doing it.

      1. I didn’t get the feeling he was talking down that much. I think people took it that way. Perhaps a bit of culture clash going on here.

        Motors aren’t that hard to repair. It’s just that knowing where to get parts is often a problem ( is IMHO a good place to start). They don’t fail often enough that most people fix enough of them to learn all the tricks of the trade as it were. It’s a good useful skill to have though.

        Though rewinding would have some definite geek points, many places don’t figure it’s economical for most small motors. The replacements are just too cheap compared to the time needed to do it. Getting the learning experience if you’re doing it for yourself can make it worthwhile.

      2. I just spent a week changing the engine in my car. A bunch of gear head mechanics stood on the sidelines and just laughed when I would do something wrong.

        He didnt mean to be derogatory, I apologize. But I still want a lesson in motor winding.

  2. WD40 is a terrible lubricant, thanks to it being mostly kerosene, which evaporates quickly, leaving a whole lot of nothing to do the job. sewing machine oil/3-in-1 oil, or even powdered graphite would be miles better for making the fan last longer on those terribad sleeve bearings.

    1. It is my understanding that WD40 is used more to loosen and clean than actually lubricate. It’s suppose to dissipate so that the “now cleaned” parts can be properly lubed with something that works better with the parts in question.

      1. WD-40 is only useful as a water dispersant. Got wet parts that need to be something other than wet? Hose them down (or dip them) in WD-40, and the water problem is gone!

        Seriously. The stuff is awesome for this role.

        Leave your tools in the driveway after a cloudburst interrupts your car repair session? No problem: Use some WD-40, and they’ll never get a chance to oxidize and form any meaningful rust. Snowblower dies because of melting snow fouling the ignition system? Solved.

        But for everything else… As a lubricant, it’s totally lousy. As a a penetrating oil, it’s just as bad. As a rust-preventative, it barely works. As a rust-remover, I daresay it doesn’t work. And on bearings? Fuhgettaboutit.

        For squeaking hinges, at home or in the car (or suspension bushings for that matter), try white lithium grease (or plain old paraffin wax, if disassembly is an option).

        For small bearings of all types, try Tri-Flow or SAE-30 motor oil.

        3-in-1 Oil(tm) is no good long term for things that spin rapidly and/or get hot. It does free up rusted things fairly well (though it doesn’t have awesome penetration), but also contains linseed oil which becomes a solid eventually (by design). Works great on a pair of box-joint pliers or dikes or other hand tools (oil once and forget about it for several years of smooth operation), but not so much as a machine lubricant. (Hint: Linoleum tile is made from linseed oil.)

        The same folks who make 3-in-1 also offer a motor oil in a similar container, but it’s just non-detergent SAE-30…which is not dissimilar to the non-detergent SAE-30 available by the quart in a discount store near you. The packaging is nice and convenient, though, which makes it easy to use. It’s distinctly appropriate for lubricating electric motor bearings, and can easily make the tiny bearings in a computer fan live for another half-decade or more.

        Tri-Flow is awesome for all kinds of stuff, since it actively dissolves oxidation and is thin enough to penetrate, but it has PTFE (Teflon) solids which can piss off close-tolerance things. YMMV, but I find that Tri-Flow is everything that WD-40 claims to be (but isn’t). OTOH, Tri-Flow is expensive enough to be used either sparingly or for only for important projects (at least on my budget).

        But again: WD-40? Never. At best, it’s a temporary fix, since once the kerosene evaporates there’s very little oil left over. Sometimes I think I’m the only person still alive who has used it for what it does best: To disperse water and keep it away long enough for a proper lubricant to be applied. (Wet rifle after a long day of hunting in the rain? WD-40 will save it, easily and quickly…though following up with something else is important.)

        WD-40 is also marginally useful as a cleaning solvent, but no better than regular (and cheap!) kerosene. And the small amount of oil it leaves behind means additional mess, which itself needs cleaned…

        For cleaning, if one isn’t in California: Cleaning parts using CRC Brak-Kleen (in the red can) is the bees knees. It is simply tetrachloroethylene in a spraycan, which is otherwise known as “dry cleaning fluid.” Only use with ventillation (ideally outdoors) and try to keep it off of your skin (it dries it out pretty well), but it washes away grease and dirt and evaporates completely and quickly.

        (I -think- I’m done ranting about WD-40 substitutions, now. Sorry for the digression.)

      2. So is WD40 the thing to reach for after dropping your cell phone in water? I’ve always wondered if WD-40 is fine for electronics. Maybe WD-40 first and then drench with brake cleaner?

      3. ^Lol @ break cleaner! I don’t know if you were being sarcastic or not, but try drenching your phone in break cleaner, and then enjoy watching it melt before your eyes… :)

    2. I have done the same thing to a couple of these fans. The problem is the sintered bearings that are used run out of oil or just goo up. Then they either seize or wear. Cleaning it out and greasing it won’t last long, I have tried it. Might get another 6 months out of it at the most. Then the year later the thing is locked up because the grease hardened.

      The ultimate solution would be to replace the bushings with ball bearings.

      1. Use better grease. Or, better, don’t use grease. :)

        As it seems like you know, sintered bronze bearings are just porous bronze soaked in oil. Sometimes a silicone-based oil, sometimes mineral.

        But whatever the case, they’re not packed with grease. (“Grease” implies a thick viscosity, which will only sit on the surface of the bearing and never really work its way into the pores as the designers intended.)

        These aren’t hardened steel wheel bearings, ball joints, or gearboxes, and grease (per se) isn’t really appropriate for these sorts of applications.

        It’d be nice to know what kind of oil (mineral or otherwise) the bearings were initially lubricated with so that the same thing could be used to replace it, but that never happens… :(

        I wrote a lot of words elsewhere under this article about replacements for WD-40 that actually work, but specific to small-electric-motor lubricants: Try simple, cheap, non-detergent SAE-30 motor oil. A single quart of it will cost less than outright replacing whatever it is you’re trying to rescue, and in these quantities will last you the rest of your life of fixing random spinning things.

        (If you have any reason to suspect that the original oil was silicone instead of mineral, then use silicone instead and you’ll be even further ahead at the start of the game. (Super-Lube is a good place to start for silicone oils that don’t suck.))

        That all said: Getting fresh oil into the sintered bronze can be difficult without complete disassembly and/or the application of heat. Chances are that by the time you’ve realized that the part is failing (or has failed), the pores are beginning to be worn shut from direct metal-on-metal contact.

        My trick, after a lot of experimentation combined with a general unwillingness to disassemble things any further than necessary: Expose at least part of the bearing. Turn the thing on. Listen. Apply somewhat more oil than ought to be necessary, to wash out accumulated dust. Listen. Keep the thing on. Wait. Apply more oil. Wait longer (hours, at least). Listen. If things are still sounding like a well-oiled machine, wipe it all down and button it up, otherwise rinse and repeat again.

        It’s not always a one-shot job, but I’ve simply not lost a sintered-bronze sleeve bearing on a fan since I started doing it this way: Some of them are still service nearly a decade later, and NONE have failed — including the exhaust blower on my furnace, which I haven’t had to touch in the four years since I worked some oil into it after it woke me up on an extremely cold Sunday with the horrible screech of a dry bearing. Indeed, I trust my relubricated bearings more than I do new (“sealed”) parts, since (in my experience) they last longer after I’ve done my thing to them than they do with the original oil (or lack thereof).

        YMMV; this is mine.

        1. They don’t even use sintered bronze in these things. They use sintered iron. About as cheap of a bearing as you can get.

          It is a petroleum based oil, you can tell by the smell. Silicones are only for where plastics and other organic materials are involved like metal on plastic, never metal on metal. When silicones are use galling can happen.

          I tried multiple different lubricants. Everything from #6 spindle oil to Kluber Synthetic NBU15 at $35 for a little tube. The problem is once the bushing wears it is all over with. The inner surface of the bushing becomes burnished and plugged Even if you set up a pressure pot to resaturate the bushing it will still have no flow.

          One could bore out the existing bushing and press in and ream a new sintered bronze bearing to replace it. Might be worth a try. I have two of these fans dead now.

  3. So you mean yo tell me my arc reactor broke because the damn fuse blew? Unfrickinngbelievable. Screw this, I’m just going to go queue up my atom smasher and make my own element. And now for something completely different…

    A fuse ends up being the fix? Right now I can see someone trying to get a refund and being told no because it’s out of warranty. Gotta love diy’ing.

  4. So glad to see people in “first world” nations doing this sort of work.
    When I lived in the Dominican Republic, if a mobile phone went bad it was probably repaired, if a fan like this broke it was definitely repaired. They fixed almost anything they could, I remember seeing an oscilloscope sitting on an old oil drum while a guy soldiered on an old motherboard to fix an older computer- who does that in the USA commercially? No one, we just throw it out and buy another piece of supposedly unfixable junk to replace it.

    1. This.

      I believe it’s because throwing it away and getting a new one is cheaper, faster, and may involve less hassle.

      That, and the convenience generation mostly has no idea how stuff works, or even how to fix it. I’ve seen people my age (25) with popped off bycicle chains, just pushing the thing down a country road, when popping the chain back on would usually take at most a stick and two minutes.

      It’s a sad state really, people become so dependent on specialists… my water pump broke the other month, on a saturday evening, and the kid watched while I opened the sucker up, found a burned out bearing, and sortakinda fixed it with liberal amounts of grease. Ran fine until monday anyway, when I sourched an old pump from the scrapyard and replaced the motor assembly.

      Cost savings: About 200 bucks. Sunday repairpeople rape your wallet.

      1. My favorite example: Folks driving around with crushed-in bumper covers on their cars.

        I mean: Yeah, sure. I’ve backed into things, too. It’s likely to happen to anyone eventually, and the modern result is a squished bumper cover.

        But a modern car has a plastic bumper cover. If you catch it in time, all you have to do is reach your hand in there, push it back out, and call it a day. If it’s a very new car, chances are the paint is still elastic enough that it hasn’t cracked and it looks -perfect- once you just push the plastic back to where it wants to be.

        Yet, I see these folks driving around this way (aka “pushing their bicycle”), and just think: Are we, as a populace, really so inept?

        To be clear: When I spot a friend of mine with with such a problem, I just fix it for them. If it’s been pushed in for awhile and the plastic has taken a set, sometimes I use a heat gun to coerce the plastic back to its original shape (which it’s inclined to be in anyway). Simple, fast, free.

        And I’ll stop to help a dude with an improperly-aligned bicycle chain (or a loose plug wire, or a dead battery, or… I’ve usually got some tools and random parts with me.)

        I once fixed a bad (so resistive it was smoking instead of starting the engine!) negative battery terminal in the parking lot of a Wal-Mart using just a pocket knife and a wrench, and no additional parts, for complete a stranger.

        What bothers me is not the problems, but that these random acts of kindness and semi-permanent fixes always result in an awe-shucks, “why-didn’t-I-think-of-that” look that makes me feel very sad for society.

        And seriously. Why didn’t they think of that?

      2. So very true.
        The (unspoken) rule in my home growing up has been “If you want X as a hobby, you have to be able to fix it.”

        Oh, camera shutter is sticky? Learn camera repair.
        Tube radio doesn’t work? Restore it.
        Car doesn’t start? Diagnose.
        Motorcycle missing license plate bracket? Fabricate one!

        Come to think of it, the only reason I can afford all of these darn projects is because I do the work myself!

      3. The problem with simply tossing a quality product that is fixable and buying a replacement is this: even products with the same brand name manufacturer, same or similar model number, often are not made the same. Sometimes they are made of cheaper materials in places where quality is a lesser concern: cut costs and ride as long as possible on accumulated reputation. When you order replacement parts for some products, you quickly learn that what used to be a good, high quality part is now replaced by a low quality part made from materials of questionable durability.

    2. To be honest, I even have still functioning computer main boards, which I probably have to junk. Just because they are too old and memory upgrades are more expensive than a new board. So I can’t use them any more.
      Although I normally try to repair devices if possible and at least remotely economic.
      Once I had to disassemble the transformer of a small clock radio to replace the thermal fuse. This got killed by a broken neutral in a 3 phase system (up to 400V instead of 230V). The manufacturer said: “throw it away, this was so cheap that we don’t even have a service manual or any spare parts”. Luckily the thermal fuse was somehow accessible.
      Another transformer (30yr old HiFi receiver) could not be disassembled far enough to access the ends of the primary, so no chance to replace it without rewinding. Which I did not want for a device which costs about 80 to 100 Euros.

      1. Want to add: The receiver was not mine and the owner said a repair shall not cost more than 50 Euro. That may or may not have been sufficient for a new transformer, but this was not available any more from the manufacturer, so no easy option.

  5. Good stuff to know. where would one find this thermal fuse? It may not be “rocket science” but i bet it’s applicable to much more expensive motors. And that’s WAAAY COOL.

  6. Done many! Why is it oiling one of these throwaways often just gets gummed up in two weeks.
    I have decades old fans no problem, what’s in those fans and all that harbour freight stuff. Timed life oil-grease sticky goo. Those vertical axis fans are very ornery, two I returned to the trash, one more to go and that’s it for me. The focus of this post is the thermal fuse. Those seemed to arrive with PLASTIC coffee makers and all sorts of heat producing appliances. They used to have thermostats and over-temp safety in a metal or Bakelite housing. Then (the plastic the Earth over with trash) people came and with the insurance industry in arms they created the thermal bomb (fuze-fuse) time bomb. One deviation, death! Buy more! The End.

  7. Thermal fuses are everywhere these days, and in heating appliances like coffee makers, electric jugs and blow heaters they are often the final (second or third) line of defense against the appliance actually catching fire.

    They come in a range of different temperatures depending on the application, and they are often the only thing actually wrong – I must have replaced hundreds.

    Ones like this could be soldered in, but they are normally crimped because of temperature, and have to handle high currents, so re-crimping correctly in heating applications is critical.

    There is a quite stunning amount of good gear that gets junked for very minor reasons, and sometimes no reason at all, just “upgraded”. If you have a few repair skills there is a handy little income to be made from a sideline repairing stuff other people throw away.

    Now, paradoxically, I see Hack-A-Day as part of this throw-away can’t-fix-a-bike-chain problem. Technical malaprops such as calling an induction motor “brushless AC” are far too common here because HaD writers lack a depth of technical experience.

    The infatuation with PIC’s and other programmable devices has actually got to the absurd point of using an Arduino for a task better suited to a triple-5; and only a couple of weeks ago an “educational” infrared detector that hid the operation of a synchronous detector in 700 lines of code, and better done with a quad op-amp anyway. PIC’s and ASIC’s are a growing cause of things being unrepairable.

    Not everything is a neat hack; some are just plain stupid, and should be published and called out for what they are – but that would require experience that the HaD editorial crew obviously lack, so the injection of a bit of real world sanity is left to grumpy old buggers like me.

    I would particularly like to thank cutandpaste for sharing his experience with lubricants.

    1. “Technical malaprops such as calling an induction motor “brushless AC” are far too common here because HaD writers lack a depth of technical experience.”

      Once upon a time, we all lacked a clue or two.

      I understand the sentiment, but complaining about a lack of proper nomenclature is like complaining about how a generation of TTL users seldom distinguished the difference between a heated cathode and a heated filament. Does the average pic user ever think of PNP vs NPN?

      Teach. Amuse. Instigate. Warn. Regale. Edify.

      But whatever you do, don’t waste time bemoaning ignorance – you’ll fare no better than plato did, and he was arguably one of the most widely read bloggers of his time. :)

      “so the injection of a bit of real world sanity is left to grumpy old buggers like me.”

      “Pots and Kettles” I say. Sanity is pretty subjective, and the minute you claim wisdom is more important than making mistakes, you have joined the coprolite continuum.

      I say: bring on the amateur dentists and the “recycled DVD laser cosmetic surgeons”, the authors who barely understand what they have just done, the barely-legal rockets that CATO on demand, the UAVs and robo music, the gasoline powered rectal flouroscopes, the phase coherers made of jello and whatever retro-art project JH is working on this month.

      HAD’s staff has greatly improved with regards to spelling and grammar – it no longer gets in the way. That’s good enough for most.

    2. “If you have a few repair skills there is a handy little income to be made from a sideline repairing stuff other people throw away.”

      I actually make a pretty decent living doing just this, in addition to the repairs I do for people that actually want to save their own equipment, rather than replace it. It’s nice to dictate your own work hours… :)

    3. I have to admit, I’m a bit behind the PIC & AVR curve – I want my understanding of basic logic gates to be better first.

      So, when I encountered an interesting problem to solve:
      “Build an Break-Beam IR detection system that will turn on a 12V computer fan for approximately 20 minutes”

      I used a 555, coupled to a simple photo-transistor & 2N2222 dark sensor.
      No doubt, it could have been a little smaller with uController – but I didn’t have to reinvent the wheel either.

    4. There was a project some days ago about a PIR sensor operated lamp. It used a PIR sensor module with a BISS0001 and added a “Trinket” adafruit microcontroller PCB. I asked: “Why” because I used a similar module some days ago. Answer: “Because I did not know if the BISS0001 can handle a time out of 1-2 minutes”. The usual cheap chinese module is adjustable with a trimpot from 2,5s to 250s, accurate probably 10% plus the capacitor.
      I use a microcontroller only if really necessary or if it gives real benefit as I prefer a circuit over having to code.

  8. “If you can’t fix it, you don’t own it”
    I too have had to open up a fan “induction” motor only to find the so-called bearings gummed up. One of my favorite fans made it a habit of gumming up just as I was needing it. I’ve tried just about every form of lubricant known to man. I finally just drilled a 0.060″ hole thru the housing and squirted a few drops of oil into it to get it running fine for another 6-10 months. Beats tearing it down every time I wanted to use it.
    I have a blower motor for my HVAC system that has places for oil to be added periodically. It’s 30 yrs old and still runs great.

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