Question about Craftsman 6" Bench Grinder with Lamp

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Older sears bench grinder wont run 1/3 hp model 397 19581

This grinder hums and will not turn when plugged in unless you give it a spin. i dont have a wiring diagram and the wiring had been disconnected for years. the motor has no capacitor and no centrifugal switch but it does have a black rectangual looking item . i think it is a starter relay switch but i have no way of knowing how to test it or to hook it up. the windings coming off the motor consist of two larger wires and two smaller wires.the two larger wires are yellow and red and the two smaller wires are black and white. i have heard of two other grinders having this problem but i have no other like item to compare this grinder with to know how to correctly attach the wires. any help would be appreciated. a wiring diagram would be helpful. thanks Does anyone have a good (cheap) source for the relay?

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  • jnahman May 31, 2009

    You are correct...the schematic lists it as a relay but it is or contains a starter capacitor. The motor starts but runs very slowly but never picks up to its full rated speed. Klixon describes it as "The Klixon 4CR current type motor starting
    relay is a compact, high capacity relay,
    designed for universal application to splitphase
    and capacitor start, single-phase
    motors with start-winding currents up to 25
    amperes."

  • jnahman May 31, 2009

    That is the problem. The two replacements I've found run $45 and $85. The grinder isn't worth that much. I was hoping to find one for only a couple of bucks.

  • jnahman May 31, 2009

    The current part is a Klixon 2cr14-224. I have talked to several companies and from what I can decipher, the replacement part is a Klixon 4CR20 (the 4CR being the replacement. Another company told me that the 7CR1-724 might work. While the table from the Klixon 4CR lists many relay characteristics, it looks like that the 4CR726 has a Max Pick U of 15.4 and Min Drop Out at 12.7 while the 4CR724 has 15.0 and 12.4 respectively. There is no listing for the 4CR20. This stuff confuses me in that those who want to sell me a high priced relay come up with different relay replacement numbers (maybe depending on wheat they have since I've been told by two companies that it was the last one they had before they have to sell me the relay in batches of 50 or 100). Sorry for the long post...hope this is helpful and not as confusing as I feel it is.
    jaime

  • jnahman May 31, 2009

    Charlie,


    I really appreciate your effort and attention..thanks a bunch. here is the link:


    http://www.sensata.com/klixon/motor-prot...

  • jnahman May 31, 2009

    Thanks Charlie,
    I had seen that one too but given all the different model numbers, I wasn't sure but for the price I had figured I'd try it if nothing more exact showed up.


    Again, thanks for all the help.


    jaime

  • Samuel Charles Spriggs May 11, 2010

    Here's my thinking. If the relay is bad, you won't get a hum, and it wouldn't run at all. Don't know why there would be a relay on this motor -- no reason for one.



    So, my guess is the black rectangular thing is the start capacitor. Is it molded with the terminals surrounded with an epoxy/plastic looking material?

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I know this is an old post, but maybe it will help others looking for information.

I have the Craftsman 1/3-HP grinder models: 397.19580 & 397.19581.

They are Split-Phase single voltage (115 V), and use a Klixon start-up current style relay - 2CR14-224.

The relay is normally open. When the large starting current in the main/run winding circuit is sensed by the the relay coil (term 3 & 4) which is in series with the main winding, the relay contacts close (term 2 & 4).

The one end of the start-up winding is connected to the main coil's BLK wire in the coil pack.

When the relay contacts close the start-up winding is energized. The start-up coil is used to provide a boost to over-come the resting inertia of the rotor.

Once the rotor reaches between 65% - 75% of operating speed, the current through the main winding circuit is reduced to the point that the relay coil cannot over come the return-springs force, acting on the relay contact arm. With the contacts open, the start-up winding is no longer energized.

This should take about 2-3 seconds, if the relay malfunctions, the high current through the start-up windings (thin wires) may be damaged.

Here is a diagram I have made.
older sears bench grinder wont run 1/3 hp model 39 - older-sears-bench-grinder-wont-run-1-3-z1zi3msqm0xxzvze3v341n5r-4-0.jpg

Klixon 2CR relays are no longer available.

You may find a suitable replacement here:
http://www.herbach.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=HAR&Product_

Posted on Feb 24, 2016

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  • Master
  • 1,489 Answers

Can you get a replacement? If not, we could probably figure out some suitable substitute.

Charlie

Posted on May 31, 2009

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SOURCE: older sears bench grinder wont run 1/3 hp model 397 19581

Hi again, OK, Well since I don't have a wiring diagram and the colors don't help. I am also going to assume it is 110VAC. The larger wires are probably the run or primary, it you remember which ones were connected it will help with polarizing. ( getting it to run in the right direction as well as the start and primary working together). You can use the two terminal switch but you should use a three wire cord. Use the switch to break the neutral and ground the case. The connections should be as follows: Connection 1, would have one of the primaries and one of the starts to neutral. Connection 2, the other start to the relay. Connection 3, the coil side of the relay to the remaining primary. ( if the relay has two connections on one end and one on the other it would be the single) Connection 4, the 3rd position on the relay to hot. That is how a split phase is wired. You may find a simple wiring diagram on the net if you type split phase motor wiring diagram. Good Luck to you, this should Fixya!

Posted on Mar 04, 2009

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Older sears bench grinder wont run 1/3 hp model 397 19581


Hi again, OK, Well since I don't have a wiring diagram and the colors don't help. I am also going to assume it is 110VAC. The larger wires are probably the run or primary, it you remember which ones were connected it will help with polarizing. ( getting it to run in the right direction as well as the start and primary working together). You can use the two terminal switch but you should use a three wire cord. Use the switch to break the neutral and ground the case. The connections should be as follows: Connection 1, would have one of the primaries and one of the starts to neutral. Connection 2, the other start to the relay. Connection 3, the coil side of the relay to the remaining primary. ( if the relay has two connections on one end and one on the other it would be the single) Connection 4, the 3rd position on the relay to hot. That is how a split phase is wired. You may find a simple wiring diagram on the net if you type split phase motor wiring diagram. Good Luck to you, this should Fixya!

Mar 04, 2009 | Grinders

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