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Thread: S W speedo

  1. #1

    Default S W speedo

    How/what controls the magnet on the side of this speedometer.?
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  2. #2
    Join Date
    Jul 2002
    North Hills, CA and Pine Grove, CA


    You have a Police speedometer. The magnet is the needle lock. A button on the handlebar engages it. Another button on the side of the dash cover releases it.
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  3. #3


    Like Chris said, that is the speedometer hand lock SOLENOID. It's a coil of fine copper wire wrapped around a tubular center/core. When a button is pushed on the handlebars, current flows through the coil, magnetizing it and pulling the spring loaded end plate down (which is attached to the plunger inside the hollow core). The plate gets latched in the energized position by the spring loaded clip on the plate end. Meanwhile, the rubber tip of the plunger is being held firmly against the speedometer needle wheel inside of the speed effectively locking it in its position the moment that the button was pushed. A purely mechanical button protruding from the left side of the dash cover acts on the plate latch and releases it from its locked position and freeing the needle as well.

  4. #4
    Join Date
    Sep 2005
    Sarasota, Florida


    Was that S-W solenoid 'tattle tale' available to the public? Seems like it was a popular feature on Corbin speedos.
    Eric Smith
    AMCA #886

  5. #5


    Thanks . What kind of button on the handle bars (right/left side?) would have been used to energize the coil?

  6. #6


    Same as the horn button but on the opposite end of the handlebars.
    Last edited by MMasa; 12-16-2017 at 01:56 PM. Reason: Changed a word for clarity.

  7. #7
    Join Date
    Aug 2004
    Beautiful Northern New Mexico


    The coil was energized by a contact terminal on the dash. The button grounded it and completed the circuit. They came in 6V and 12V versions.

    The pursuit light switch is also mounted on the right side

    Robbie Knight Amca #2736

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