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Author Topic: Repairing fans  (Read 621 times)

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Zebidee

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Repairing fans
« on: October 18, 2022, 12:19:18 pm »
I've been diversifying my electrical repair skills, away from arcade applications to other things.

Last few days have been all about fans - the kind that you turn on on a hot day.

We have many fans at our place, which is in a tropical, humid area. In addition to a few ceiling fans, we have maybe 8 pedestal fans in regular use (across 3 houses and work/play areas), with some of them operating most of the day and night.

These fans obviously take a lot or wear and, over years of use, start to have troubles. They become slow to start, or don't start at all.

Mostly when a fan starts getting tired I will put a small amount of fine machine oil (like you might use on a sewing machine or a hair clippers) into the spindle, and work that in to get things turning again.

Sometimes I need to change the "run" and/or "start" capacitors (little box-shaped guys at the back of the fan). These caps are typically 0.5uF to 5uF. Smaller fans may only have one cap, some larger fans may have two. In the pic below, you can see how they are often connected using wire nuts. This makes changing them easy.





However, sometimes the fans are just DEAD, and no amount of oil or new caps will change that. I had three dead fans like this in my shed.

I've now learned that these fans all had the same problem: there is a thermal fuse (2A, 130 degrees) buried inside the housing, inside the coil wiring, that blows. This is OK because it is mostly better to have a dead fan than a fire in your house.

Here is a pic of the coil exposed.





Running a fan with no lubrication or with worn out caps probably contributes to the heat and the fuse blowing, but I suspect these fuses just blow after a few years of use anyway. More on that later.

Today I fixed all three fans by replacing this fuse (also a little oil, and one capacitor).

After I've carefully cut away the string/cable ties and pulled the wires out a bit, you can see the fuse. In this pic I can already tell it is blown (red at bottom, carbon scoring).





As it turns out, there are at least two tricks involved with replacing these suckers.

First trick is you have to be really really careful, because the fuses are actually wired into the coil itself. The coil consists of superfine copper wire with enamel insulation. You don't want to cut or break or pull hard on this, because then it will be a bugger to repair.

You will need to cut away some string or cable ties to access the fuse, so you have to be very careful and take your time. You don't want to damage the copper wires!

Second trick is that soldering a new thermal fuse in is not simple. The fuse is rated to blow at 130 degrees, and most people solder at about 350 degrees! I screwed this up the first time because I forgot :)

So, two parts. First is to use a lower temperature for your soldering iron. I used 250 degrees. But obviously this is still well above 130.

So, it needs a heat drain or sink as well, to keep the soldering heat away from the fuse. I used my CRT anode discharge cable for this, a bit of ground wire about 1m long with alligator clips on each end. Attached one clip near the fuse, and another clip near the soldering action.

Check out the discolouration (from excess heat) on the thermal insulation!





Once you are done soldering, test that the fuse is still good with meter. Also good idea to check that the coil is still good (multimeter/ohms across the AC plug pins, there should be connectivity with some significant resistance).

I'm going to leave you with this pic of three thermal fuses I replaced today, with a good fuse for comparison. The fuse on the left is good/new, and you can see it has a healthy clear/pinkish colour underneath. The two on the right are completely blown, and the colour beneath is quite orange/red. Far right is from the fan pictured above, which is a little larger and clearly got quite hot.





The fuse 2nd from left is the most interesting. This is because it is only partly blown, on the way out. There is definitely some red built up around the leads, but looks mostly OK. This fuse tested bad at first, then tested good again when I jiggled it a bit. I replaced it anyway, fan is happy again :D

Hope this helps some people save their fans from landfill :D
« Last Edit: October 18, 2022, 12:34:44 pm by Zebidee »
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Xiaou2

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Re: Repairing fans
« Reply #1 on: October 19, 2022, 03:59:35 pm »
Look again.

 Most of the failure of these types of Fans,  is from wear on the bearings and or Shaft.

 Once the metal starts to wear, things no longer line up... and it causes issues, and Failure... because there is
very little clearance between the Rotor, and the Electromagnet housing.   The Rotor gets all scratched up and worn.

 The bearing itself.. usually isnt ball-bearing,  so it cant be easily repaired.   And even if you had the perfect bearing
replacement size... by that time, the shaft (and possibly also the rotor) has usually taken damage as well... so its a lost cause.

 At that stage, you would need a replacement rotor assembly, and new bearings... and unless you have spares around,
its usually cheaper to buy a completely new fan.


 The electrical side, while interesting... is typically the result of the worn bearings and seized motor, causing the fuse to blow...
which often means, its too late.

 The exception is, if the fan was just so Dirty, that the dust was causing it to seize,  rather than it being Wear-Related.

 Oil on the shaft and bearings, will typically only extend a worn device, a few more months of use.   The fan-noise, will quickly return,
and eventually, the motor will stop and start, randomly... until it eventually seizes up again.


 So, check for smooth rolling bearings... if they are ball-bearings.  Check the shaft for wear... and see if there is any Wiggle / Play  when the rotor
is mounted in the bearings.  Check the Rotor for wear, which could effect the performance and generate excess heat.  Check the
electromagnetic housing for wear.

 Also, a lot of the heavier duty motors, will also have their own self-cooling fins, internally.  Make sure all of the fins are there, and clean them,
and the entire motor, of dust and any potential carbon soot.

 If the motor is not a brushless motor... check the carbon brush lengths left.  They are spring loaded.  Many brush motors, have replacement
brushes... and if not,  they can be custom made / ordered.
as well as cleaning the excess carbon dust off of the rotor / contacts.
« Last Edit: October 19, 2022, 04:14:20 pm by Xiaou2 »

Zebidee

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Re: Repairing fans
« Reply #2 on: October 19, 2022, 06:47:03 pm »
Geez Steve. Most of your talk is irrelevant to modern AC fans.

Note that modern household AC fans are brushless, and the rotor is air-gapped from the stator.

Three main reasons for a household fan to fail are:

1. Needs a clean and some oil on the front and rear bearings

The bearing do wear out over time, but regular maintenance (clean, 1-2 drops of oil each year) makes them last much much much longer. Fan bearings that have seized (due to no oil) can often be revived by working some oil into them.

2. The start and/or run capacitors wear out.

Capacitor performance degrades over time and circumstance. Easy to measure with capacitance setting on a multimeter.
These are cheap and very easy to replace.

3. The thermal fuse in the coil blows.

Fan was running hot, most likely because it needed some oil and maybe a new capacitor.
So, deal with problems 1 & 2 first. Then replace the thermal fuse.

Replacing the thermal fuse is, as I've explained above, can be done but you need awareness, patience and gentle hands. With experience, should take less than an hour or so to do all the steps above, including the fuse.

This is why many repair guys/gals will just say "coil is blown" or "rotator seized" or some rubbish, because they either don't know or won't be bothered with it.

...its usually cheaper to buy a completely new fan.

This is what the manufacturers WANT you to think, so you go out and buy a new fan (and throw old one into landfill). It is called inbuilt obsolescence. This is why they use a cheap thermal fuse that dies over time regardless, that doesn't reset itself, and is a PITA to replace.

We've gotta fight this ---That which is odiferous and causeth plants to grow---. Fight for a "circular economy" n stuff.

The capacitors and fuses are cheap, <$1 each, much cheaper than even a cheap fan.
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Xiaou2

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Re: Repairing fans
« Reply #3 on: October 21, 2022, 09:31:55 pm »
No dude.  I have an expensive Ozone + Ion generator.   Its powerful enough to handle smoke damages, from a fire.
I got it fairly cheap, because it was partially damaged,  and it was a fairly easy repair.

 It worked for many years.. but then the AC motor on it  (BRUSHLESS)  ,stopped spinning.
I tore the Entire thing apart, thinking I could fix it.

 The bearings ... NOT BALL BEARINGS  !!!  Just solid metal, with a Hole in it...  have become worn to the point, where there
was physical "PLAY" in the shaft.   That Play, caused the Rotor to grind part of itself off, by grinding into the magnet housing, as a result.

 There is No physical way to repair it, without getting a new Bearing, and possible a new Rotor, due to the damages this one suffered...


 Yes, Preventative Maintenance is Key in helping to avoid Pre-Mature wear.  But Metal spinning on Metal.. will eventually wear, no matter
what you do.   And once that wear had gotten to a certain point... Oil will not "Fix" the issue.


 Now... I managed to find a blower motor, that has the same exact bearings, so that was good... but, the Rotor on the blower motor
is much longer, and wont fit the smaller motor housing.  Then I managed to break one of the Fanblades off somehow (I think
the parts box probably fell over)  Yay.

Zebidee

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Re: Repairing fans
« Reply #4 on: October 21, 2022, 10:29:53 pm »
These fans have the same kind of bearings, Steve. Like a sleeve. Yes they will wear out eventually. Maybe after 10 years or more of solid use.

Things is, you buy a cheap new fan for about $30-$40. It probably has a 1 year warranty. Then it dies after 2-3 years! The manufacturers know this, but they don't care. Because most people will just go get a new fan, so more profits for big business $$$. That is how the system works, but it is very wasteful.

With a little maintenance (preventative is best) and/or repair, you can get a full 10 years or even more out of the same fan.
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danny_galaga

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Re: Repairing fans
« Reply #5 on: October 24, 2022, 06:14:30 am »
Very commendable work Zebidee. Just be mindful of liability on repaired AC equipment. If the fan housings are plastic, no sweat. But if metal, be extra careful.


ROUGHING UP THE SUSPECT SINCE 1981

Zebidee

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Re: Repairing fans
« Reply #6 on: October 24, 2022, 07:18:12 am »
Very commendable work Zebidee. Just be mindful of liability on repaired AC equipment. If the fan housings are plastic, no sweat. But if metal, be extra careful.

Thanks Danny.

You raise a very good point. Even though the fans I was working on have a plastic outer shell, for safety you should check that there is no connectivity between the either of the two AC pins and the metal housing for the coil & rotor. Or any other outer metal parts of the fan.

For a basic test to see if the coil/fuse is OK: with meter on ohms, there should be connectivity but some significant resistance (maybe ~1/2 Mohm to several or more Mohms) between the two AC pins while fan is switched to "on" position (but not plugged in, obviously).
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Mike A

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Re: Repairing fans
« Reply #7 on: October 24, 2022, 08:34:58 am »
That just makes it dual purpose.

Cooling fan and bug zapper.

danny_galaga

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Re: Repairing fans
« Reply #8 on: October 24, 2022, 09:06:18 pm »
That just makes it dual purpose.

Cooling fan and bug zapper.

😄

On a serious note, I remember a young enthusiastic manager at at tyre shop had repaired a bench grinder himself. Unfortunately an apprentice was electrocuted and died. The manager went to gaol for manslaughter.


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Xiaou2

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Re: Repairing fans
« Reply #9 on: October 27, 2022, 05:28:32 am »
Quote
Things is, you buy a cheap new fan for about $30-$40. It probably has a 1 year warranty. Then it dies after 2-3 years! The manufacturers know this, but they don't care. Because most people will just go get a new fan, so more profits for big business $$$. That is how the system works, but it is very wasteful.

With a little maintenance (preventative is best) and/or repair, you can get a full 10 years or even more out of the same fan.


 Ive never seen a fan die that quickly.  Not ever close to that short of a timeframe.

 But here is the thing... Lifespan partially depends on Environment.

 If your fan is in a Hot climate, with lots of Dust... then yeah, that fan is going to be getting seriously clogged up with
dust and dirt.  The extra heat, will cause the metals to expand, and make things wear quicker.

 And if the fan blades are coated in oil.. so that Grime sticks to them... it will put additional strain, as well as an
Imbalance force, on the shaft and bearings... which will again, quickly wear things out.

 That said... if the thing cakes up with dust so quickly, it can die well before any bearing wear.


 Where I live, the climate is mostly moderate... And, I kept my device indoors, in a low dust environment.
The fan itself, was also in a box with Air Filters, which prevents the dust from easily clogging up the fan.
Im pretty sure it made it well over 8yrs of continuous daily running.

Zebidee

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Re: Repairing fans
« Reply #10 on: October 27, 2022, 08:08:59 am »
Where I live, the climate is mostly moderate... And, I kept my device indoors, in a low dust environment.
The fan itself, was also in a box with Air Filters, which prevents the dust from easily clogging up the fan.
Im pretty sure it made it well over 8yrs of continuous daily running.

Imagine how much longer your fans will last with a little maintenance.

Check out my completed projects!