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Proper Wiring of Old Washing Machine Motor

  1. Apr 29, 2012 #1
    I recently purchased an old small drill press. It hosts a retasked old washing machine motor as the power source. Only problem is that the wiring was snafu, and I could use some help with that.

    This is a FSP motor, 115 volt 1725 rpm, 1/3 horsepower.

    The motor input wiring are to a set of 5 numbered and color coded spade lugs on a black bakelite pod. The terminals are 1 - red, 2 - red, 4 - blue, 5 - white, and 6 - black. There is no terminal 3 that I can find. The bakelite pod is screwed into the motor and has a switch arm out the bottom in contact with a normal centrifugal switch mounted on the motor shaft. There are only 3 motor wires, black, yellow and blue, and they appear to be associated with the terminals as blue motor wire (4), black motor wire (6) and yellow motor wire (5).

    With the switch in the static (low rpm) position, there is only continuity between terminals (4) and (5), and the resistance is 2 ohms.

    With the switch in the running (high rpm) position, there is continuity between (4) and (5) at 2.5 ohms now, and also between (4) and (6) also 2.5 ohms, between (5) and (6) at 0.7 ohms, and between (1) and (2) at 0.9 ohms.

    When I apply 110 volt power to terminals (4) and (5), the motor runs. What bothers me is that I guess that a run capacitor should be present, but across which terminals is the question. Also, I am troubled by the second apparent circuit energized by the centrifugal switch. If the primary were only a start circuit, it should disable when the centrifugal switch closes, but it does not. I do not think I want a high torque drill press motor so if there really are two parallel sets of windings in this motor, I don't think I want both. However, as comments in other threads seemed to indicate, they thought the second circuit was used at low speed for additional torque, which does not jive at all with the circuit readings above. This seems to energize the second circuit at high speed.

    Can anyone give more than a guess as to where a run capacitor should be installed and what the function of the second apparent motor circuit enabled by the centrifugal switch might be? My gut says put the capacitor between terminals (1) and (2) and to externally jumper terminals (4) and (6) together (i.e. put power across both (4) and (5) and (6) and (5)), but I am leery to try this for fear of fireworks and a burnt up motor.

  2. jcsd
  3. Apr 30, 2012 #2
    It would be almost impossible without more info to figure this out safely. Do you know what washing machine model this came from, or can you post either a pic or all of the nameplate information from the motor. We could then likely do a web search and find a proper wiring diagram. Guessing, as you say, could lead to a really bad day... (I'm actually kind of surprised that a small wiring diagram wasn't on the inside of the electrical cover, or on the motor nameplate. That is the norm.)
  4. May 1, 2012 #3

    jim hardy

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    Gold Member

    if you're lucky it's color coded and numbered per the NEMA standard

    see if this link is of any help
    http://www.electricmotorwarehouse.com/motor_connection_diagrams.htm [Broken]

    and this one is a tutorial with same info but explanations.
    old jim
    Last edited by a moderator: May 6, 2017
  5. May 1, 2012 #4
    Thanks, but going to drop this one. Googled everything on the motor nameplate and got nothing. Even tried a parts outfit but FSP part numbers are difficult to check, need the OEM make and model, and that is long lost.

    Did find one reference that helps.


    This suggests the centrifugal switch is bad, and is not opening up the start windings at running speed. That may be why the drill press got the heave ho. Also it looked like someone had been trying to figure out the wiring as it was a jury rig of taped together twisted connections using 110 volt lamp cord and a 3 prong grounded plug with the ground pin yanked out.

    Anyway, the reference says the start windings should be cut out as soon as the centrifugal switch closes, and you know, when I first tested it I thought it did that, but now it does not seem to do so. In any event I have other small pump and compressor motors lying around, and can replace the jury rig, it was all the challenge of fixing it.

    My personal experience is that these old motors are considerably more helver-stout than more modern ones, and so long as they are kept lubricated, will run forever. Shame to have to throw one away.
  6. May 1, 2012 #5
    Jim Hardy: Thaks, somehow I thought I was on a different thread, and it was your 2nd reference that turned the trick. I took the bakelite puck out, completely, and very carefully worked out the circuit connectivity, with the centrifugal switch open and closed, and came to the conclusion that the switch was working fine and indeed shuttting off the start winding as soon as the motor spins up. Wired 110 volt power across terminals 4 and 5 (like I did before) and let it run for half an hour. The motor warmed up to what feels like a normal operating temperature. All the other terminals and colors and numbers were simply red herrings, not required at all as best I can tell. My new (old) drill press is happy again.

    Thanks, your circuit diagram did the trick. No capacitor required and this is the simplest and oldest single speed motor made, with a separate start winding. Even the colors threw me, who would wire main power to blue and white, when there are black and white terminals present? And then there are the red terminals, probably serving some other function in the old washer. Oh well . . .
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