Last summer, our refrigerator stopped working. Alarmed that the entire contents of the fridge may be lost, we moved everything from the freezer to another freezer that was in the pantry. But the contents of the refrigerator were more of a problem. A couple of picnic coolers would suffice for a couple of hours, but not for days.
My son (a student in a university EE program) and I disassembled the rear of the freezer section, and we found the condenser coils frozen, so they were working correctly. The actual cause of the failure was that the circulating fan had stopped. Without the circulating fan, the cold air from the coils does not chill either the freezer or the refrigerator section below. The appliance was crippled.
Thinking the motor bearings might be seized, we took out the motor to lubricate it, and we found that the fan turned easily. It was not the bearings. When we checked the continuity of the motor windings, we discovered that it was an open circuit.
At least now we knew we had to replace the motor. It would take two or three days for the new motor to arrive, and, in the meantime, we would have no refrigerator. This is a big deal when you have four boys living at home.
While I went online to find a replacement for the motor, my son, not knowing any better, decided to unwrap the insulation tape on the motor and see what he could do. The motor has hundreds of turns of fine enameled wire, about 32 gauge, on a plastic core. I figured an open circuit was probably buried under dozens of layers. However, upon removing the tape, my son found an obviously melted wire on the surface of the windings.
I thought this would be a great time to explain to him what happens when a transformer gets one shorted turn. Magnetically, this one turn shorted out the whole transformer, which is why there was enough energy to melt the copper wire into metal balls. The enameled insulation was so thin that the motor vibration must have been enough to chafe the insulation of two adjacent or overlapping wires, causing a shorted turn, which then melted to form an open circuit.
My son did not assume my belief that the motor was ruined, and proceeded to unwrap about two turns in each direction. He asked me to solder it back together. Finally, a light bulb went off. I realized that you can repair small motors if you can access the bad windings, so we soldered the wires back together, and voila! The motor worked again. It had three fewer windings, but out of, say, 300 windings, this is a miniscule change.
We were able to reassemble the refrigerator/freezer and get the food chilling. The lesson? Don’t assume it’s impossible just because you've never done it before. The spare motor arrived three days later. It’s in the shop now, waiting for the next (unfixable) failure.
This entry was submitted by Chris Kelly and edited by Rob Spiegel.
Chris Kelly holds a BS from the University of New Mexico and an MS in computer science from Colorado State University. He has served as a design engineer with Agilent Technology since 1983, and he designs small electronic instruments, such as function generators, and DMMs. He has been named on six US patents in the areas of data acquisition and conversion, instrument calibration, and signal generation.
Tell us your experience in solving a knotty engineering problem. Send stories to Rob Spiegel for Sherlock Ohms.
I love the ingenuity and tenacity of your son and the way he choose to ride it out until the two of you could come up with a solution. No doubt a budding engineer! Hopefully, this was a great hands-on learning experience for both father and son, both from a technical standpoint as well as fostering broader problem-solving skills.
Like others, I too, have had similar experiences fixing "stuff." I hope all our experiences are symptomatic of a spirit of willingness to try to fix things instead of running out to buy a new model which many times is no better or even worse than what we are trying to fix. In that spirit, opportunities abound, and here in the Chicago area, an entrepreneur has expanded his 16 year old company (corecentricsolutions.com, Think Green division) to include the remanufacture of "no longer serviced" parts for appliances such as stoves, refrigerators, etc. This gives the DIYer a chance to keep equipment running. As the Brits would say, "Full marks" to all of those willing to try to fix a broken, but otherwise good piece of gear.
Great story. When I was younger I did something similar for a dishwasher. I ended up rebuilding the pump motor. It didn't really take too long. As I remember, my father was just too impatient, so my mother sent him outside while I finished the job.
I really do prefer to repair an appliance or machine if it can be done in a reliable way. We have a double oven which developed a problem. I isolated it to a part in the electronic control module. Frankly, I think I could have fixed that myself, but becuase of the high temperatures involved I wanted the module replaced or professionally repaired. We called in the GE (it is a GE oven) repair service. The guy came by, came to the same conclusion as I had, and then informed that the module was no longer made so he could not help me. They did not charge me. The options were to replace the oven or fix the module. Oh, and the replacement units were slightly larger, so we would have to modify the cabinetry. The cost would be about $2K or more. I opted to fix the module. I found that one of the companies that did this was located nearby. I took the unit in myself and they had it ready the next day. We reinstalled it and it works great.
Thanks for the note. I think you hit it on the head, impatience. I get driven by cost-effective, efficient use of time, etc, but sometimes the home solution has different parameters than at work. Saving the contents of the fridge was a happy event worth way more than any costs involved. As Beth pointed out, my son's tenacity was more effective than my experience and snap judgement. Maybe that comes from the time he spent watching bugs and enjoying the world through patient, curious eyes!
This is a bit of a tangent, biy I had a vaguely similar problem.
The problem was described as the slab break detection sensor causing an emergency stop on a gang saw - sort of like an oversize bread slicer for granite blocks - the 'slices' come out 2 inches thick by about 6 feet x 8 feet. I had never seen a gang saw before, let alone fixed one. After the operator showed me the problem, I reviewed the schematic, and the slab break sensor was not tied into the emergency stop circuit. The error code traced back to an inverter alarm - over-voltage. By roundabout descriptions, when the slab break is detected, the drive motor (and 8 foot diameter flywheel) is braked to a stop. That was when the symptoms finally pointed to the braking resistors for the inverter. There were 3 braking resistors, and one had a burnt-out section. I spliced the resistor back together - less one turn to remove the burnt section. And then the slab break sensor problem was fixed.
Hey, Glenn, your story would make a good Sherlock Ohms posting. Could you give a little more detail (step-by-step on identifying the problem, step-by-step on solving the problem)?
Good thinking on the young man's part. You never know whether or not you can fix something until you at least take a look. The fans in refrigerators are notorious for premature deaths. A 9-year-old Kenmore at a friend's house has gone through three fans. After the last one went, the fridge got replaced with one that has a higher efficiency and smaller doors that make it easier to open in a small kitchen. Sometimes even though you can fix it, you might have a good reason not to.
I've never been facile enough to repair/re-solder bad windings in either a motor or a transformer. The fact that you guys diagnosed the problem is great, but that's only half the problem. The other half is fixing it. I admit that there are many cases where I've figured out the problem, but in attempting to fix it, I've mucked things up worse. A VCR comes to mind, where the plastic gears inside were so touchy that when the thing was reassembled it just wouldn't cycle properly. Sometimes broke is broke.
You're not alone, Alex. I had the same experience with a CD player that held three disks. The small plastic gears were fragile and difficult to get back together. It was easier to buy a new player. Back when cars had carburators I took one apart ro rebuild it and followed the instructions faithfully, but it never worked well. After a while I replaced it.
I just thought of a medical analogy that's apropos. It's like when doctors say, "The patient survived the surgery but died from complications." Sometimes, I admit, it's lack of patience (not "patient") on my part when attempting to repair stuff. But mostly, like you and I have both experienced, Jon, lots of things are designed to be put together and fit tightly, but not to be taken apart and put together again. Humpty Dumpty.
While it's great to be able to fix something, these days things aren't made to last and are made rather poorly, as the possibility that vibration may have been able to rub insulation off shows. Stuff like this makes me wary of everything produced these days, especially as price is king, and standards such as ISO 900X, mere window dressing to make people think that the Emporer is wearing clothes.
As my neighbors throw out their appliances, they are always so proud of the mountains of cardboard in their "recycle" bins. I, on the other hand, take more of your son's approach. Instead of recycling the box of my new appliance - I "recycle" the appliance - back into a working appliance.
In this day of micro electronics and planned obsolecence we have forgotten the true value of time saved "not shopping", things learned while fixing other things, experience gained by failure, perserverance and patience learned while overcoming the adversity of an un-repairable dishwasher.
Small wonder then that our nation begins to lose it's technological edge as there is no longer the necessity to learn these basic skills, fundimental concepts, and problem solving experience with the ease of a "just replace it" society. (Maybe our kids are just following our example?)
I am constantly amazed when people explain why they can't fix something. "I don't have the tools" (2 screw drivers, a wire cutter and a pliers? $5.99 @walmart) "I don't know anything about it" ( 5min + google). "I'm afraid I'll wreck it more." (said as it's being hauled out to the garbage). "Did you even try to fix it?" (Not really cause I want new model XYZ). "I don't have the time." (But I'll spend 3 hours talking to salespeople and shopping on line and 6 hours working to pay it off + gas and time to drive all over town for the best deal, paying income tax, paying sales tax, paying credit card fees, + supporting Overseas jobs. Oh sure most of my solutions involve 3 trips to my local hardware store - but I consider them more like friends.
We can blame our schools and government for the technological decline in America, but the core problem has to do with our society's attitude and how badly we want/ or need to know something. With the internet and all this country has to offer in libraries, senior citizens, and community education there is no reason anyone in this country cannot learn to do whatever their heart desires to learn, if you don't believe it just ask anyone who comes from just about any other country.
I applaud your article - this story used to be the norm, now it's so rare it merits an article. Thanks for showing us why we need to "keep our hands in it."
We seemed to slide into the no-fix-it mentality when kids stopped taking home-ec and shop in school and when parents became so protective they wouldn't let their kids "do stuff" that involved tools, chemicals, or electricity. I grew up in the Sputkin era when kids tinkered with cars, built electrical and electronic "stuff," and experimented with chemistry sets in basement labs. Thomas Edison was my hero.
My brothers and I used hand tools and watched our dad, uncle, and grandfather make and fix things. A friend's dad had a small metal lathe, drill press, and other tools that we felt comfortable around and learned to use. Mom used to complain that my brother Chris and I brought home more junk from the local dump than we took. We disassembled washing machines and lawnmowers for motors and stripped TVs and radios for parts--that is, if we couldn't repair them.
Unless we instill a hands-on do-it-yourself attitude in young people fewer and fewer adults will have the interest or aptitude to fix things, let alone design them.
I'm with you on this one, Jon. If I didn't have the willingness to fix things, my first car -- a Corvair -- would not have lasted two weeks. I literally had a rubber band holding the choke in place. I grew up believing that you first try it fix it yourself before taking it in for repair. It was pretty much culture-wide when I was a kid.
By the way, gift subscriptions to Popular Science or Popular Mechanics (perhaps both!) might spark a kid's interest in DYI projects and learning how to use tools. I just learned an interesting trick to silence noisy chains in the March issue of PM.
Good idea for a gift, Jon. There are also a number of new science shows on TV these days. Even "Mythbusters" gets into a bit of science and engineering.
Hi, Rob. Although toy stores don't sell chemistry sets today, parents can buy many fun kits and activity "packages" for kids interested in science and technology. Science Kit lists many, as does Ramsey Electronics and Jameco Electronics. Perhaps some CAD-and-animation experts can create graphic "construction" projects that let kids assemble a small motor in virtual space. The software would include the pieces and have the kids assemble them in the right order to create something that works. Simple projects such as a wind-powered generator, weed-wacker 2-cycle engine, small generator, and so on would get kits interested enough they could start to do things with real tools. Lightwave 3D, for example, can create and animate solid objects nicely.
Good suggestions, Jon. It was a tad easier when I was a kid and there were tons of science-based toys. There were also tons of build-it-yourself kits such as Heathkit. Heathkit is still around, but it's not as easily available as before.
Yes, having kits for kids is a good thing but it's not essential. My first major repair job while still a child was fixing my parents' Toastmaster pop up toaster which had served us since my infancy. I was around 12 years old. I could see a break in the heating element near the edge of the mica board that held it in place. I knew that soldering wouldn't mend it as the nichrome wire got incandescent and would certainly melt the joint. It hadn't occured to me, back then, that vaporized lead might also be rather toxic in a toaster! Anyhow the lead free repair required that I enlarge the slot in the mica board so I could pull through sufficient nichrome wire to be able to crimp the ends together. You wouldn't have expected that repair to last but it did until well into my college years!
They just don't make appliances as well as they used to!
As an aside, the cost of power tubes used in broadcast transmitters has skyrocketed of late making tubes less practical than transistors even though high power solid state RF amplifiers have traditionally been way more expensive to build. The principle reason seems to be a global shortage of raw materials to fabricate power tubes, mostly a lack of quality tungsten wire for cathode filaments.
Hello, bdcst. Your toaster fix reminded me of a story my grandfather told me years ago. He was the principal at a New York City school years ago and many of the kids took vocational classes in which they built projects. One fellow showed up with a toaster he built at home entirely on his own, but my grandfather would not let him plug it it. He had made it of wood.
Did you know you can fix incandescdent light bulbs? My mother told me her sister used to able to do that during the WWII rationing. One day my little transformer-powered high intensity light (remember them?) burned out. I could see the fat, little, broken filament through the clear class. I turned on the power and tapped the unit so the two bits of filament vibrated past each other. Then bingo! they touched and welded together.
It lasted about a week. The second time I did this, it lasted about 15 minutes when an entire section dropped out of the middle. End of story for that one.
Give an incandescent light bulb a whack with a soft-soled shoe and you'll increase the light output... at least briefly. Probably easier to get a higher-wattage bulb, but hurry, they won't be available much longer if the US Congress has its way.
Jon Titus mentioned "DYI" projects. LOL! Are those the "Do Yourself Injury" ones? I've had a few of those over the last 50-odd years. Don't even ask me about the suggestion I get the dents out of a 1000 gallon oil tank by pumping 30psi of air into it... that woke up the entire neighborhood, and I live out in the country, (fortunately) hundreds of feet from any neighbor's stuff.
I do prefer the "DIY" projects, though, especially the ones that might not pencil out for time spent, but definitely help educate the kids.
And that oil tank? One half is a burn barrel now. I keep it as a reminder.
Perhaps many engineers share similar "philosophies" of life, and I find all these replies interesting, especially the note that fixing an appliance is better than replacing it (at least up to a point) and that this is, in fact, the ultimate in living green, not having to recycle because you're not yet "done" with the item in question, because you fixed it!
I expect to fix as many household items as possible rather than pay to have them repaired or throw them away/recycle them and buy a replacement. It makes economic sense as well. But while I grew up in the era of building go-karts from old lawnmower engines, then fixing my own car when I got one, I have to say that many consumer items are simply not repairable, like digital cameras or cellphones. We are designing instruments these days with ball-grid-array ICs that have 1100 pins, on circuit boards that have buried traces and "blind vias" that almost defy imagination to troubleshoot and fix.
On the other hand, it's not always the complexity of the technology that causes a disposable mentality; sometimes it is just the shabby components used, such as the motor winding wire that has thin or brittle insulation that fails. It only has to last to the end of the warrantee period... We didn't make stuff that way in decades gone by; it wasn't made to last 100 years, but it was made to last. The shabby parts make for a shabby product. Why should a refrigerator fail after only 2 or 3 years service? My parents had a Westinghouse refrigerator for 40 years or more that never needed more service than cleaning the condensor coils.
There are classes of product (smart phones?) that may never be repairable, and besides, evolving RF standards will obsolete them eventually. But that is no reason to make everything else in the cheapest, most shabby way, and maybe my best response is to buy a higher quality electric drill (or whatever) that WILL last, and support manufacturers that build them.
Like an old Navy Chief used to say - "what's it gonna do, not work?"
Maybe I'm showing my geek, but someone tossing out a 'broke' appliance was giving me a gift! Bigger problem was where to put it at home...
Guess things are different these days, but you don't learn medicine by keeping your hands clean. Grab the broke gear and tear into it, find out what and where.
I am impressed that the repair was that simple. What I have been finding for a few years now is that the design skimps on copper and skimps on iron, and so when the line voltage rises a bit the iron saturates and the current rises and there is a failure exactly as described. Of course, sometimes poor insulation makes things fail even faster. But the most common response of the manufacturer has been to put in a nonresettable thermal fuse, usually implanted in the winding where it is hard to find. REmoving the failed thermal fuse and adding a regular fuse will often repair the system, and assure that it is still safe and won't start a fire if it fails. Of course on many occasions the thermal fuse just gets bypassed. Yes, the product may fail again some time, but I have not had it happen yet.
I am wondering where these thermal fuses come from, they usually have no markings, and I really wonder where I can buy some of them. My guess is that they are poorly calibrated and that is what causes the failures.
Well let's see last week I fixed an oven control board for an Engineering professor. Cleaned the contacts under one of the controls. Today I fixed his portable CD player. That only took a little super glue. My brother emailed me yesterday wanting to know if I could look at some of the camera monitors for his church tha thave problems. Not sure I can help there.
Talking about getting kids interested in tinkering again, there is a great magazine called MAKE that is helping to fuel a new wave of tinkerers and DIY selfers.
Any toaster or other incandescent nichrome wire/ribbon separation can easily be repaired. It entails making sure the parts are in contact at the break point. Then put a little borax on the break area and plug the appliance in. The borax will allow the break to fuse and produce a permanent weld, making the unit functional again. I have used this method to repair heaters and scientific instruments over the years.
A while back, my wife's 1999 Plymouth Voyager started to have a problem with the intermittent wipers. The were in fact "intermittent" in a bad way.
I started with the service manual and found that none of the resistor array voltages in the multifunction switch (used to control headlights, wipers etc.) matched the service manual. The body control unit (BCU) measures a voltage on one wire to detect the switch position, saving having 8 wires for the switch.
Great, I found the problem! After buying the $175 (non-refundable) part from the dealer I measured the replacement switch. Same resistance as the old one accross every section of the switch. Whoa, whats going on here? So Installed the new part anyway, figuring that luck would take over from this point. Nope, no such luck.
I proceeded to test the system again and again and noted that the wipers almost never parked themselves along the same location on the glass, sometimes being quite off the mark.
I then noticed that when the wipers landed near the very bottom of the glass in the normal position, the intermittent mode of the wiper system would start and run reliably. This was very perplexing. Concerned that I had a mechanical problem or that the motor had a parking switch that did not work, I looked further. But, the schematic did not show any parking switch, just sense connections back to the BCU. One thing did catch my eye, there were two relays, one for high/low speed and one to power on the motor.
The power relay was wired in a weird fashion. The motor lead was attached to the common pole of the relay and NO contact was wired to +12V as expected, the other NC to ground. A light came on in my head. I switched the two relays and the system worked fine! But why?
Think before looking below>
When the relay powers off, the grounded contact of the relay shorts the motor to ground causing a generator braking action. Because the generated current is brief, that relay contact tends to get a bit of corrosion and not clean itself as it would with normal current. Because the BCU does not see that terminal go low, it assumes a failure mode.
I contacted Haynes, the author of the service manual and they apologized for the misprint on the switch resistor values and actually sent me a corrected page.
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