Assistance wiring a 3 speed box fan rotary switch

Discussion in 'General Electronics Chat' started by Grenadineflaps, Sep 11, 2016.

  1. Grenadineflaps

    Thread Starter New Member

    Sep 11, 2016
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    I am attempting to replace a Lasko box fan 3 speed rotary switch. I was wondering if anyone could help me determine: a) if this switch has the same capabilities as the original, and b) how to wire it up.

    I am confused because the replacement switch only has 4 input terminals, while the original has 6. If I need to include a 120v on/off switch into the circuit I have the switch already, and would like wiring instructions, too. Thank you!

    [​IMG]

    [​IMG]

    The replacement switch pictured below has 2 terminals on each side:
    [​IMG]

    [​IMG]

     
  2. Grenadineflaps

    Thread Starter New Member

    Sep 11, 2016
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  3. Grenadineflaps

    Thread Starter New Member

    Sep 11, 2016
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    Is this diagram correct if I use my own on/off switch?
    image_62549.jpg
     
  4. SLK001

    Senior Member

    Nov 29, 2011
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    The neutral is just a thru on the original switch. Your schematic is correct, except the on-off switch is probably not needed. Check the new switch to see if there are 4 positions. If so, one of them is "OFF".
     
    Tonyr1084 likes this.
  5. Grenadineflaps

    Thread Starter New Member

    Sep 11, 2016
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    How annoying, after all of that work it wasn't the switch that was bad. It must be the motor, or some other component I am not familiar with. I tested the new switch and it was doing its job. I might as well spend the $30 on a new one.

    I never included this info but I found this fan in the trash and thought I could bring it back to life. The motor wasn't seized up so I assumed it was good.
     
  6. RockySax

    New Member

    Dec 5, 2017
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    20180329_192447.jpg My cheapo box fan has parts that look exactly the same as the pics above. I took it apart and continued until only the motor windings and connecting wires were left. Inside the motor, the connection covered by a white fiberglass thread tube turned out to be a fuseable link which had blown. It was an "ELCUT UMI Microtemp Thermal Fuse Axial Type 122 TF Cutoff 115℃ 2A 250V". I found these on eBay, $4 for 5 of them and I'll be waiting a month to receive them. Sure, it's easier to get a new fan at this point, but kind of fun to troubleshoot. And be very careful when you take apart the motor housing! There are very small windings which are very easy to break (I broke two). The replacement fuse (and any broken wires) will need to be carefully soldered into place.
     
    Last edited: Apr 6, 2018
  7. RockySax

    New Member

    Dec 5, 2017
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    A couple more pics 20180330_015439.jpg 20180329_200003.jpg
     
  8. dendad

    Well-Known Member

    Feb 20, 2016
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    While it is in pieces, lubricate the bearings. I find that dried out bearings are a big problem with fans.
     
    Tonyr1084 likes this.
  9. MisterBill2

    Well-Known Member

    Jan 23, 2018
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    Dried out and sticking bearings are indeed a source of trouble in fans. And those thermal fuses are a close second source of grief! I was going to also suggest that the capacitor, that black plastic block with the two wires, might be a problem. 2 years ago I rescued a very nice 24 inch industrial quality fan, $149 at Graingers, and the problem was a failed resistor in the electronic speed controller. The wire lead had broken off because of vibration. A new resistor with some silicone to prevent the vibration and I have a great fan. So a lot of "rescue" devices are quite repairable. The secret is to not spend money fixing them.
     
  10. Tonyr1084

    Well-Known Member

    Sep 24, 2015
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    I've seen many a failed fan. The #1 most common was dry bearings that cause the fan to stick. Even if it turns, it doesn't turn at full speed which causes it to overheat. The #2 failure is the fusible link, which burns out because of failure #1. Clean the bearings and lubricate them (NOT with WD-40) and replace the fusible link with the SAME VALUE fusible link and the fan should be good for another season of blowing.

    Mom's washer failed because of a fusible link. Initial numbers indicated the rated link would blow at 105% of normal operation. I believe it was a built-in flaw. Would cost $135 for a new mechanism. Would cost another $300 to pay an appliance service tech to install the guts. I fixed it for less than $2.00 with a Radio Shack bought fusible link. Only I chose a rating of 146% of normal operation.

    In the engineering world, 133% is common engineering practice for some high end commercial equipment. 150% is common for industry equipment where human life is at stake in the event of failure, aircraft, automotive and medical equipment. 105% isn't something I'd want for a kids toy. It's GOING to fail.

    In the case of your fan - order the correct fusible link and replace it. WARNING: DON'T ATTEMPT TO SOLDER IT IN. YOU'LL BURN IT OUT! I speak from experience. Not ashamed to admit my mistakes. Neighbors heater failed. Fusible link. I attempted to solder in a new FL. Fortunately I bought five of them. So I had a second chance. (third, fourth and fifth if I didn't learn fast enough)
     
  11. SLK001

    Senior Member

    Nov 29, 2011
    1,166
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    I found a fan just like this one. It was a bad fusible link due to hair and balloon ribbons wrapped around the shaft. However, the wiring was held in with zip ties, so fixing the thing then re-zipping it, I managed to break some of the windings of the motor - too many to try to fix. I was really upset, because I already had plans for that fan! Ended up gutting all the good parts and trashing the thing.
     
  12. jorge258mx

    New Member

    Aug 8, 2018
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  13. sdowney717

    Well-Known Member

    Jul 18, 2012
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    I piked up a thrown away nice tall fan. The bearings were dry and tight and it caused the thermal fuse to blow.
    I lubed fan with synthetic engine oil. I simply bypassed the fuse, it has worked well for years, likely 10 years ago I fixed it.
     
  14. KeepItSimpleStupid

    Distinguished Member

    Mar 4, 2014
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  15. MisterBill2

    Well-Known Member

    Jan 23, 2018
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    What is important with the switch is that only one output at a time is on. There are switches for lights that switch on combinations of outputs, which is fine for lights but it will destroy the motor in a minute or two, because of short circuiting part of the winding. So that is a check to make before using a replacement switch.It should only connect one wire at a time, never more than one.And it is vital to be gentle with the wires to th motor to avoid breaking them off. As some folks have discovered the painful way.
     
  16. Tonyr1084

    Well-Known Member

    Sep 24, 2015
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    Using zip ties is a bad way to construct (or repair) a motor coil winding. Lacing cord is the way to go. Only make sure it's not something that can catch fire because the coils WILL get warm. Hot even.

    One solution I've often used for lacing up a wiring project is to use dental floss. It's strong but flexible. I've even used it to sew holes in my tent. Or you could just buy lacing cord. But I would never use zip ties on something so delicate as the motor windings of a fan.
     
  17. Steve El

    New Member

    Oct 1, 2012
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    RELATED - I want to convert my 3-speed box fan to a single speed. My plan was to bypass my failed 3-way switch by simply connecting the neutrals, and adding a toggle switch I happened to have lying around, using only the hot and one wire to the motor. Anyone see any problems with that approach?
     
  18. MisterBill2

    Well-Known Member

    Jan 23, 2018
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    My very first suggestion is to be sure that it is the switch that has failed! Many times it is the capacitor that fails, so that the motor will not start. I have also had a power cord develop an open circuit with no apparent damage. So use an ohm meter with a low enough range to show clearly the difference between a contact closure and ten ohms of winding resistance. Then put one ohm-meter lead to the line terminal on the switch and check the resistance to each of the other three terminals in each of the four switch positions. At each position there should be only one zero resistance connection.Once that reading is made, verify continuity from the line terminal to one plug pin, and some higher resistance to the other plug pin. A broken line cord is usually much simpler to fix. But if it really is a failed switch, then a failed switch then a simple two-wire switch to replace one of the positions should work well.
    AND AN OOPS on my part, which I did not realize that the post I responded to was not a part of the original discussion. Thus, it should indeed have been started as another discussion. But my response applies to both.
     
    Last edited: Aug 15, 2018
  19. Tonyr1084

    Well-Known Member

    Sep 24, 2015
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    If you convert a 3 speed into a single speed with a toggle then the other two speeds (other two wires[assuming only two others]) need to be dead ended, capped off and made sure they don't contact anything else. Not any part of metal, not any part of any other electrical circuit. Otherwise you're going to get a sudden and energetic surprise.

    Perhaps you should start your own thread about how to safely go about rewiring a 3 speed fan into a single speed fan, as opposed to hijacking someone else's thread.
     
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