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Raiku's Ceiling Fan Repair Adventure

Note:  This page deals with whirling mechanical devices that can take your finger off, and AC power that could start a fire or cause electrocution.   I do not guarantee that any of this information is accurate.  Should you decide to use this information, be warned that legally speaking, I am neither an engineer nor an electrician, and any damage you do to yourself, your fan, your house, etc. is entirely your responsibility, and you cannot ever even think about suing me.  If you do think about suing me, you will be so consumed with guilt that you'll only achieve a good night's sleep after doing penance, which will consist of rubbing jalapeno peppers on your nether regions.

Way back in that legendary decade known as the 80's, (its hard to believe so many years have passed!) two ceiling fans were purchased by my parents.  They were not expensive fans, by any means, they were cheap imports.  Model U-42 manufactured by SMC in Hong Kong, to be precise.  One was installed in my room at their house, and the other was put into storage, either because my mother changed her mind about what she wanted done (as she is prone to do), or because my father just bought two because they were on sale (as he is prone to do).  The precise details are lost to the mists of time and memory.  In any case, the second fan came out of storage and was installed in my current abode, about 14 years ago, when I first moved in.  It served me well, for many years.  One day, roughly 1999-ish, I tugged on its chain, and my faithful friend didn't respond.  So begins the quest to avoid purchasing another fan, because disposable-good consumerism is not our friend! 

My first step was to simply purchase another switch.  I was, at the time, unfamiliar with the precise details of how speed control switches worked on ceilings fans, and I simply assumed the oft-tugged mechanical switch had failed.  I trusted our friendly local neighborhood fan-accessory salesman, and purchased the switch he assured me was correct for my fan.  Carefully transferring the wires in order, L - 1 - 2 - 3, I proceeded to pull the chain and.... nothing.  Another pull, got a nasty electrical pop.  Another pull, and the fan hummed and didn't turn..  Another pull, and off again.  I was content to let well enough alone, but the summers were a bit warm in the family room, and cold in the living room, without the ceiling fan to circulate the cold air from the window AC evenly.  In early 2004 I decided that my friend must be repaired properly.  A bit of consulting with appliance repair people, and a bit of internet research, convinced me that either the switch was incorrect, or the dual-section capacitor had failed.  I decided to try the capacitor first, as the switch had been replaced already.    I found a near-exact replacement at the local appliance store, and installed it.  Once again, the same results... 2 offs, one nasty pop, and one hum.  It must be the switch!

This time, I decided to do some proper research.  Google turned up a few Usenet and web-board posts with stories similar to mine.  I continued to dig, and eventually discovered that there are several variations on ceiling fan design, motor type, and speed control method.  I also discovered that some people collect ceiling fans, although I couldn't find my exact model listed by anyone.  A trip to a local fan and light specialist store revealed that most certainly my off-the-shelf switch was incorrect, and that they could supply the correct one, by dissecting the original and examining the contact patterns and cams.  One problem remained:  In the intervening 5 years, I'd misplaced the original switch.  This is the cool bit:  Since my parents had a working version in my old room, I could show them that one.  I borrowed its switch module, and let them examine it, under strict orders not to dissect anything they couldn't put back together.  They called their switch supplier, who knew precisely which switch I needed, and promised me they'd order me one within the week.  If only they were so speedy.

Fast forward 3 months.  They finally ordered the thing, after many phone calls reminding them I needed it.  In the mean time, I've been using my parent's fan switch, since they don't even like ceiling fans blowing on them.  They insisted I could leave them with dangling wires, or that they'd just buy a new fan, but no, that wouldn't do.  I had to have both fans working properly!  $8 obtained my long-awaited prize, and I set about installing it post-haste.  Afterwards, I double checked to make sure all wiring was correct, using my working example as a reference.  I pulled the chain and.... nothing.  and again, nothing, and so on.  At one point I got a bit of a pop, but that was all.  I refused to be defeated!  My hamster-style electrical-fu is stronger! 

Perhaps the switch was incorrect?  I felt I had a good understanding of the theory of operation of my particular variety of fan circuit.  Two windings, two sections in one capacitor, and 3 speeds, accomplished by varying the amount of capacitance in series with one of the windings, and thereby varying the phase delay.  That is important, I think, to understand:  various posts I had stumbled across incorrectly stated that the capacitors somehow vary voltage or resistance.  That is simply not so, its all about phase delay!  The more capacitance, the more the AC waveform is delayed on one winding, and the more torque is developed.  The trick, you see, is that the motor is operating near to stalling.  AC has a fixed frequency, and the motor has a fixed number of poles, so if it were operating synchronous, or near synchronous, you'd be stuck at or near one RPM.  What this style ceiling fan does, is operate far down the curve near to stalling out, so that it is nowhere near in synch.  The weight and drag of the blades and heavy rotor design, I think, help with this.  Its genius, really, because it allows a cheap switch and a cheap 2-section capacitor to give us 3 speeds on fixed-frequency AC.  Ok, so I'm a geek and I appreciate that.  You should too.

Now, back  to my problem.  I thought and thought about it, and poked around, and eventually decided to map out the wiring diagram properly, just to be sure.  I also decided to compare the switches, using an ohm meter.  I checked the working switch first, starting with it turned "off", and checked continuity between all the terminals.  Then I checked the non-working switch.  They were, indeed, identical, and here is what I found:

It was really starting to make sense now, how this thing worked.  The black wire was "hot", the red went to one of the motor windings, and the other two positions went to each section of the capacitor, which then connected its common side to the remaining motor winding.  One winding in phase with the AC power line, one with a phase delay due to the series capacitance.  Here is a more complete diagram of how this style ceiling fan is wired, with the switch in the "off" position:

One problem remained:  The unit with the replacement switch and capacitor still didn't work, although I checked the wiring carefully!  I realized there was one component I hadn't checked, nor suspected, since it is so rarely used.  It isn't in the above diagrams, for clarity, but it is in the next one, which is essentially a complete schematic of my fan, and probably many other similar models.  The reverse switch was defective!  It was also defective the "good" unit, although I simply left it in the "down" position year round, and never worried much about having it move the air upwards.  I knew the switches couldn't be worn out, since they are never moved, so I took them apart to see what was up.  They were typical DPDT slide switches, with metal tabs bent down to clamp them together.  Easy to take apart and reassemble.  Once inside, it I saw the problem.  Twenty years of aging had turned the small amount of grease inside into hard putty!  I cleaned both reverse switches with rubbing alcohol, replaced the grease with some modern lithium grease, and reassembled.  Success!  Both fans now are completely operational!  (caution:  if you ever find yourself cleaning switch contacts, remember that both alcohol and a certain all-purpose name-brand cleaner and lubricant that everyone has in their garage is flammable, and that switches spark!)  Here is the final schematic for a typical 3-speed reversible fan with capacitor speed control:

Update, July 2007: Since I put this page up in 2004, I've recieved quite a few emails from intrepid adventurers bravely fighting against the forces of entropy and the culture of disposable consumerism. To those of you who have said thanks, you're quite welcome. I have also recieved a few inquiries regarding the replacement pull-chain switch I purchased. If your fan has the same schematic as mine (check it three times to be sure!), then the switch you need is a Zing Ear ZE-208S A05. This seems to be most frequently refered to in the industry as simply an A05. Mine was purchased at a local lighting / fan store, so I have no idea if it is possible to order small quantities (for instance, just one!) directly from the manufacturer.