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Size (temperature) of a Thermal fuse for a shop vac motor

Discussion in 'General Electronics Chat' started by Bill Kinley, Apr 27, 2009.

  1. Bill Kinley

    Bill Kinley New Member

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    My shop vac stopped working and I diagnosed the problem to be a blown thermal fuse. I have checked with the manufacturer and other sources and haven't come up with the size to replace it.

    Personally I don't have a clue, but I suspect it is less than 100 degrees Celsius. Does anyone know or have any suggestions?

    Thanks,
    Bill
     
  2. gerty

    gerty Member

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    There should be a part# or temp marked on it.
     
  3. Bill Kinley

    Bill Kinley New Member

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    It has no markings, actually it is a piece of metal (wire) between two electrical connections. I am assuming it is a thermal fuse, can't imagine what else it could be, anyway it interrupts the circuit not allowing it to work..
     
    Last edited: Apr 27, 2009
  4. dave

    Dave New Member

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  5. jchistia

    jchistia New Member

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    Thermal Fuse Device in Shop Vac

    I also have found discarded shop vacs with this device non-operational. My guess is that these "fuses" are included in the design because of product liability concerns. If the motor were to catch fire and consume the plastic, noxious fumes along with the possibility of fire would occur. These fuses are what I call "fail soft" devices. Unfortunately, they are not fail-soft as far as the utility of the vacuum goes. It doesn't make any difference if your vacuum is dead because the motor burned up or the fuse melted. The vacuum is considered junk either way. Too costly to take it to a repair shop. Very few of us attempt repairs and when we do, we cannot find parts. I found a similar fuse INSIDE of a condensor motor case on a Maytag rollaround portable A/C unit. The unit had to be nearly entirely disassembled to get to the fuse. The biggest challenge was to find suitable crinmp connectors as soldering is near impossible. Cost? $1.37 or the part. New unit? $600. By the way, I suspect that the "link" material in the shop vacs is no more than a length of solder. Melting points of different solders can be found at RF Cafe - Solder Properties Melting Point After fooling around with my found vacuum, I ended up bypassing the device. My 30 year old Sears Craftsman doesn't have one and is still running.
     
  6. romueller

    romueller New Member

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    same thing for me

    Just diagnosed the exact same thing on my ShopVac 90L500A. Blown fuse for which I can't find any specs. Just a piece of metal material between two contacts in an unmarked plastic holder. $100 vacuum tanked by a $0.001 piece of metal. I swear it almost looks like it was meant to wear out after a certain number of motor starts. I don't think I'll be buying ShopVac brand again. Argghhhh!
     
  7. jchistia

    jchistia New Member

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    Shop Vac "fuse" -- warranty item if < 5 years

    Shop Vac warranties their vacuum motors for 5 years home use. If you have the receipt, contact them and they should send a whole new motor. (Their accountants must have figured that a $71 motor is cheaper than a .001 cent fuse.)
     
  8. KMoffett

    KMoffett Well-Known Member

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    My guess that "home use" implies a very low duty-cycle and they can get by with cheap motors. Cheap motors heat up quickly. Thermal fuses stop cheap, over-heated motors from starting fires. :( Just out of curiosity, how long had the motor been running when it stopped?

    If they are within the 5-year warranty (But read the fine print first!), then what do you have to loose by returning them.

    ken
     
  9. Bill Kinley

    Bill Kinley New Member

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    I purchased several thermal fuses at $1.25 an installed the lowest temperature one (165 degres F, I think) I used wire nuts rather than solder. It is working fine now.
     
  10. Bill Kinley

    Bill Kinley New Member

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    I don't know how long I had it, because I have two. I suspect it is over five years old. The $1.25 thermal fuse was a quick fix, just wish I knew for sure the 165F was low enough.
     
  11. KMoffett

    KMoffett Well-Known Member

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    Bill,
    By "how long had the motor been running when it stopped?", I meant running at that moment. Five minutes?...fifteen?...an hour?
    Ken
     
  12. Bill Kinley

    Bill Kinley New Member

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    I just went to use it one day and it didn't work. I have had problems with the switch several times and just thought it was the switch, but diagnosed a problem to be the motor. After checking the windings and brushes, I found the problem to be something I thought was a thernal fuse. I replaced it a 165 ͦF thermal fuse, using small wire nuts. Now it is working fine.
     
  13. alanis

    alanis New Member

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    10 gal shop vac model 90L400

    Aunt has this vac and we are helping her out with this.

    She said she probably was using the vac an hour at least and then it just quit.

    Husband tore it apart and found this fuse? was burned up.

    Where can we buy a thermal fuse?

    What kind of vacuum should we buy for her now? She doesn't want this as she feels it will be unsafe, so we will bring it home and fix it for our shop.
    I don't think it will be a shop vac model though!! This vac was only used on weekends and a few weeks during the summer as it is used at her summer home.

    Thanks for your help,
    Alanis
     
  14. Bill Kinley

    Bill Kinley New Member

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    I did a Google search for thermal fuses and purchased several thermal fuses at $1.25 each an installed the lowest temperature one (165 degrees F, I think) I used wire nuts rather than solder. I figured 165 degrees wouldn't cause a fire and if it too low, it would blow and I would go to the next higher temperature. My largest was 100 drgrees C (212 F). be sure not to solder it in, because it may melt it.
     
  15. alanis

    alanis New Member

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    Thanks for the info Bill!

    My husband wanted to wire it directly and use it then unplug when we are done.

    How long has yours lasted since you changed the fuse?
     
  16. Bill Kinley

    Bill Kinley New Member

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    I fixed it maybe three months ago, but only use it in the garage. I expect it to last a long time.
     
  17. RD Gibb

    RD Gibb New Member

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    Resetable Thermal cutoff

    I had this same problem occur with my shop-vac. Fortunately I happened to have an old eureka vacuum cleaner with a bad cord that I didn't have the heart to throw away. I tore it apart and found the thermal cutoff screwed to the motor housing. I am not sure what the rating is on the eureka cutoff but after cutting the heat-shrink tubing off of it (to eliminate any insulation for the thermal switch) and placing it in approximately the same position as the original in my shop-vac it works great. I have not had it kick off yet and even if it does I can just let it cool down and it will reset. Hope this helps.
     
  18. KMoffett

    KMoffett Well-Known Member

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    All of the "thermal fuses" I've ever encountered are not "self resetting". They act like a normal fuse and open permanently. That's the maddening thing about them, because there are no readly available exact replacements like normal over-current fuses. :(

    Looking for a replacement for my daughter's PIZZAZZ pizza baker. I can find them but: one on eBay for $11+shipping, or 10 (minimum order) from the fuse manufacturer for $26 with shipping.

    Ken
     
    Last edited: Aug 2, 2009
  19. Bill Kinley

    Bill Kinley New Member

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  20. KMoffett

    KMoffett Well-Known Member

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    Now that looks do-able. :) Thanks! I'll bookmark that resource.

    ken
     
  21. RD Gibb

    RD Gibb New Member

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    Check out the thermal protection used in most modern household vacuum cleaners. According to the instructions supplied with said vacuums if the motor overheats the fuse will kill the motor. If this happens simply allow the motor time to cool while you clean the filters or change the bag to ensure proper airflow the fuse will reset and you are off to the races.
     

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