Roger Borg Posted January 26, 2023 Share Posted January 26, 2023 (edited) I'm trying to work up a best practices log, and insomuch, wondering the procedure for basic ELECTRICAL testing prior to applying any power, and before disassembly. Post breakdown notes are welcome too, but first things first. Meaning, when you get an untested fan, what are the first few things you should do with your meter so you don't zap yourself, or fry your new toy, and how are they done? How do you test for shorts to the metal body (motor or base)? Is it continuity from line cord to metal? What about stator or coil shorts? Once apart, are there generic resistance readings that exist for speed coils or stators? If in the neighborhood of x, that seems about right type of thing? How do readings vary for chokes, nichrome or otherwise? How do 2 or 3 speed coils vary in their readings? What about basic readings for stators? How do shaded pole, phase shift, and centrifugal start affect these numbers? Anything else I'm missing, please chime in. I've worked my way through several fans so far, but never quite understood where to begin if getting from an unknown provenance, aside from taking it all apart. As always, many thanks... Edited January 26, 2023 by Roger Borg Quote Link to comment Share on other sites More sharing options...
Stan Adams Posted January 26, 2023 Share Posted January 26, 2023 I run all of mine in series with a 500 watt light bulb & through a variac. If there is a short, the light bulb will shine vs kaboom. Quote Link to comment Share on other sites More sharing options...
Roger Borg Posted January 26, 2023 Author Share Posted January 26, 2023 6 minutes ago, Stan Adams said: I run all of mine in series with a 500 watt light bulb & through a variac. If there is a short, the light bulb will shine vs kaboom. Can you please provide a photo of your set up? (I'm a visual person, so seeing it is super helpful). Also, what if the bulb was of a lower wattage? Thanks... Quote Link to comment Share on other sites More sharing options...
Stan Adams Posted January 27, 2023 Share Posted January 27, 2023 My workbench with variac & light bulb. I built this portable for when I worked on fans at the battleship. For smaller motors I often use a 300 watt lamp or smaller. For circulators, I use two 500 watt lamps. For a 12” fan the lamp won’t glow. It will glow dimly for a 16”. If the motor is shorted, it’s full bright. 3 Quote Link to comment Share on other sites More sharing options...
Stan Adams Posted January 27, 2023 Share Posted January 27, 2023 One thing I didn’t mention, I’ve done electrical work for years. My workbench is wood & I stand on a rubber mat. I don’t like getting jolted. 1 Quote Link to comment Share on other sites More sharing options...
Tony Clayton Posted January 27, 2023 Share Posted January 27, 2023 Love your variac Stan. I have the model below yours. 2 Quote Link to comment Share on other sites More sharing options...
John McComas Posted January 27, 2023 Share Posted January 27, 2023 I'm glad you like the three meter Variac Stan! (I think it helps with your mad scientist image) 😁 1 Quote Link to comment Share on other sites More sharing options...
Stan Adams Posted January 27, 2023 Share Posted January 27, 2023 3 hours ago, John McComas said: I'm glad you like the three meter Variac Stan! (I think it helps with your mad scientist image) 😁 I love it! And I love it even more as it was given to me by a close friend who taught me a lot! I wonder who that could be? Appreciate you! 1 Quote Link to comment Share on other sites More sharing options...
Roger Borg Posted January 28, 2023 Author Share Posted January 28, 2023 I have a little bit of time this weekend and wanted to quickly diagnose a few fans without disassembling. Hoping for some feedback on checking fans with a multimeter in order to get an overview of operational condition. (I have not yet constructed Stan's in line bulb set up, so hoping for info on using multimeter in lieu of that). Specifics in first post. Thanks... Quote Link to comment Share on other sites More sharing options...
Lane Shirey Posted January 29, 2023 Share Posted January 29, 2023 (edited) In my case and in my opinion, there’s not a need for that level of information just to know if a fan is worthy of beginning the restoration. In fact, you won’t get accurate readings unless you’ve cleaned all the switch contacts, and centrifugal switch if there is one. After disassembly, first thing I do is replace the headwire. With the old headwire removed I check the stator ohms. You can get the approximate readings by searching your specific fan in the old forum. But in many cases, a reading between pairs will be somewhere between say, 20 and 150 depending on the style of motor. If I get a favorable reading and an open circuit (no contact) between any stator wire and the laminate core, then I consider it worth installing the new headwire and deem the stator ok. Yes there are cases where you can’t be that general, but usually that tact works 99% of the time. . As far as the speed coil. Only after you’ve bead blasted or cleaned all contact surfaces shiny with emery cloth or wire wheel on a dremel can you check the readings. Speed coil readings are usually in the range of say, 1 to 6 ohms. I rely on past posts to determine what the right readings should be. I usually print off that data and keep it in a binder for future reference. Keep in mind you’re likely not to get the exact same readings as they sometimes varied from the manufacturers, and the person’s meter who measured them might not have been calibrated. Roger, I know you’d like a more precise answer, but by simply using the above criteria I’ve been able to determine if a fan will run and is worth restoring. I should note is that I only run untested fans BEFORE I hand over the cash. I have no hesitation plugging a fan in at an antique store. I’ve had a few cords go “poof” and to me if the motor ran for an instant, it means a hefty discount because the shop owner will be afraid of it and want it out of the shop. If the motor smokes, well then I’m happy I didn’t buy it. But once in my hands, I don’t even test it before a teardown and restoration. On a shaded pole motor, I might be inclined to connect a test cord directly onto the motor leads, but that’s it. I hope that helps, Roger. Edited January 29, 2023 by Lane Shirey 1 Quote Link to comment Share on other sites More sharing options...
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