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Thread: Wiring a 2 speed A.O. Smith pump motor

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    Wiring a 2 speed A.O. Smith pump motor

    I recently had an A.O. Smith (aka Magnatek) 2 speed pump motor (B984) on my Challenger main pump go bad and replaced it with the same, but newer model (A.O. Smith B2984). I had 4 wires connected to the old motor: 1 green, 1 red, 2 black. The green goes to ground, and based on how it was wired on the old motor, the red went to the L2 terminal (common?) and the blacks went to the L1 (high) and A (low) terminals.

    The motor works well, but when I switch from high speed to low speed (using a Compool Cp3600 pool-spa control system), the motor still runs, but it looks & sounds like it is still on high speed. So basically, whether I push the high or low speed button on the control pad, it operates on high speed.

    How can I determine if I have the wiring correct? How do I know if the red wire is common, and which of the 2 black wires go to either the L1 or A terminal? I have a meter than I can test voltage with if needed.

    Here is a tech drawing of the motor:

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    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Wiring a 2 speed A.O. Smith pump motor

    Welcome to TFP!

    You can figure it out with a multi-meter fairly easily. There will only be voltage across one pair of wires on low, and a different pair on high. The wire that is live in both modes is the common wire, while the other wire corresponds to the speed it is live at.

    The other way to figure it out is to find the other end of that wire, presumably near the speed switch, and see how things are wired at that end.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Mod Squad Bama Rambler's Avatar
    Join Date
    Jun 2009
    SouthWest Alabama

    Re: Wiring a 2 speed A.O. Smith pump motor

    It sounds like you have it wired correctly. Did you mark the black wires before you removed them from the old motor? So you'd know which went to L1 and which went to "A". As Jason said, you should have two wires hot at a time.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
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