How to wire the switch for a bench grinder with 5 wires?

Hi. I picked up a old Montgomery Wards 6 inch bench grinder, model TDS 8131A, rated 115 volts 60 cycles 3.0 amps 3450 rpm, from a friend. The switch had gone out and was removed before it came into my possession. It has 5 wires coming from the motor: 3 black wires labeled with white tape and the numbers 1, 4, & 8, and 2 green wires with no labels. I was told it needs a capacitor to run and it came with a Mallory 270-324MFD 110VAC. My question is what type and rating of switch do I need to get and how do I figure out which wire goes where? I have searched online for a wiring diagram and / or manual but have not been able to find anything. Also, it has a caution plate on it that reads "use with time delay fuse". What is that and where can I get one? Any help is appreciated. Thanks.

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3 Answers

  • John
    Lv 7
    12 months ago
  • 12 months ago

    get your multimeter out and test the green wires for conduction to ground -- the motor housing. Test also while turning the wheel by hand.

    Then I'd consult the wiring diagram for other motors of similar size ... perhaps an a/c compressor. i suspect the run/start capacitor is wired in parallel with the main power feed and could be all wrong on that. The motor likely requires extra current to startup, which is the capacitor's function. How many leads that involves, I do not know and it may depend on the design of the motor.

    Example: after the motor starts, the normal power feed may be one of the black lines [connected to incoming hot on the load side of the switch]. the other two black lines may go to the capacitor and their function would be to add power either to a separate winding inside the motor or to the main winding. This setup owuld have the green wires as the neutral and ground.

    Another approach would be to find an active old timer who maybe remembers how these things were wired up. No idea where you'd search online, though


    Source(s): grampa
  • elhigh
    Lv 7
    12 months ago

    The time delay fuse is a slow-blow type that will allow a brief overload while the motor is pulling heavy amps as it starts up.

    I strongly suspect the green wires are your capacitor leads, but don't hold me to that.

    I think your motor is actually capable of operating safely on 115 or 230v AC, but it depends on how it's wired and you REALLY need to find out how those leads are supposed to be connected. If you could find out who manufactured the motor itself - it wasn't Montgomery Ward, and it wasn't Powr-Kraft - they could probably help you out.

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