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Thread: R90/6 tail light help

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  1. #1

    R90/6 tail light help

    Hi I have a 1975 R90/6 with a tail light not working.The brake light and blinkers all work just not the running tail light. I am not very good with electronics but I looked at the wiring and everything seems to be connected. Any help would be greatly appreciated thanks.

  2. #2
    First check the bulb, including make sure the contact on the base end of the bulb isn't corroded/eroded.

    Second, test for 12v at the tail light socket.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell

  3. #3
    I believe I have an after market tail light light set up if that helps diagnose.
    Attached Images Attached Images

  4. #4
    here is where it connects
    Attached Images Attached Images

  5. #5
    Liaison 20774's Avatar
    Join Date
    Sep 2005
    San Antonio, TX
    As Paul said, ensure you have 12v for the taillight. Remove the taillight wire, the top one. Stick a voltmeter probe into the female wire connector and touch the other probe to the frame or good ground. Turn on the ignition. You should have 12v...if not, then you need to figure out why.

    It appears that you have a separate ground path, not just the frame. So you should remove the wire marked ground and this time stick the voltmeter probe into that connector. Switch the voltmeter to measure resistance and touch the other probe to the frame or good ground. You should get zero resistance. If not, then you have a break in the ground return for the light.

    If the brakes work, then ground is probably OK. So, you'll need to figure out if you have 12v for the running lights or not.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  6. #6
    Rally Rat
    Join Date
    Dec 2011
    Fargo, North Dakota, USA
    Yup, that is NOT a stock /6 light.
    If the assembly works with everything but the tail light, Paul has the best recommendation.
    Break out the multi-meter and see if you have voltage coming from your lead.
    (My money is on a solderless connector problem)

  7. #7
    Registered User lmo1131's Avatar
    Join Date
    Jan 2010
    Pismo Beach, CA
    I am not very good with electronics but I looked at the wiring and everything seems to be connected.
    Which means you may not have a voltmeter/multimeter.

    You can find the same information with one of these... for about $6.

    It will not give you quantitative information, but it will tell you yes, or no. I keep mine in my tool tray.

    To test for presence of voltage; DISCONNECT the tail light wire. Connect the alligator clip to a ground (any point on the frame or the battery (-) terminal) and then touch the tip of the tester to the wire that feeds the tail light terminal. The light inside the tool should come on.

    To test for ground: DISCONNECT the ground wire. Connect the alligator clip to the (+) terminal on the battery, and touch the tip of the tool to the ; the light should come on.
    "It is what you discover, after you know it all, that counts." _ John Wooden
    Lew Morris
    1973 R75/5 - original owner
    1963 Dnepr

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