Tach wiring connector harness source | FerrariChat
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Tach wiring connector harness source

Discussion in '206/246' started by HMB-Dino, May 3, 2011.

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  1. HMB-Dino

    HMB-Dino Formula 3
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    Jun 28, 2010
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    Pebble Beach, CA
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    RonG
    #1 HMB-Dino, May 3, 2011
    Anyone know where to find the wiring harness that connects to the back of the tach? My "Main Beam" indicator light connector seems to be faulty (should note I don't recall if it ever worked). I measure 10-11v on the positive side of the bulb connector, but I can't get that indicator light to operate. And yes, it has a new bulb and I've tried other known good bulbs. The tach harness has these combo power/ground connectors for each indicator light and I'm clueless on how to fix w/o replacement.
     
  2. alhbln

    alhbln Formula 3
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    Adrian
    #2 alhbln, May 3, 2011
    Last edited by a moderator: Sep 7, 2017
    You can rebuild the wire harness using an TYCO 'Fastin-Faston 8 terminal male connector' and blade receptable connectors. To replace the wires going to the bulb sockets, cut and remove the heat shrink tube at the end of the connector, remove the wire and solder in a new wire (don't forget a new heat shrink tube). But the tach's wiring harness usually does not fail, except maybe if the connectors are quite corroded.

    Sounds like ground is missing on the main beam indicator bulb socket. Ground is continuously supplied via the white/black wire going to the terminal in the middle of the bulb socket.
    • Check the ground connection by measuring the contact in the middle (inside of the socket) against a good ground connection on the car while the tach is connected to the car wiring.
    • If there is no ground connection, remove the insulation from the middle terminal at the bulb socket and check the soldering and resolder, or replace the wire to the TYCO connector if necessary.
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  3. HMB-Dino

    HMB-Dino Formula 3
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    RonG
    #3 HMB-Dino, May 9, 2011
    Last edited: May 9, 2011
    I'm confused about the tach wiring for lights. For the general lighting (left and right sides), the white/blk ground wire attaches to `side' post of the plastic lamp housing and the solid white wire attaches/soldered to the center/main (+) post. But for the Main Beam indicator lamp, the ground wire attaches to the center/main (+) post and the brown striped wire to the side post. Why would they be opposite?

    When I probe, I have ~12v on the spring finger inside the lamp housing and nothing for the center contact point (with neg probe touching steering column as my ground)...this is opposite of what I would expect. Yet my tach seems to be wired the same as in your picture.

    I'm electrically challenged, but what am I missing?
     
  4. alhbln

    alhbln Formula 3
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    Mar 4, 2008
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    Berlin, Germany
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    Adrian
    #4 alhbln, May 10, 2011
    Last edited: May 10, 2011
    Someone didnt follow a pattern when creating the circuit, it looks like the permanent wiring would be on the side and the switched wire in the middle of the socket, but the Main Beam Bulb is indeed opposite. Nothing to worry about.

    When you measure the center contact (ground switched) against the steering column in "Voltage" mode, you won't see anything as there is no voltage difference between ground (center contact) and ground (steering column).

    You can
    • either measure the center contact against +12V instead (and then you should see 12V if the wiring is ok)
    • or you set your Multimeter to "Resistance/Ohm/Ω" mode when measuring the center contact against the steering column. In this mode, you should see around 0-1 Ohm if the ground wiring is ok.

    good luck,
    Adrian
     

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