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Thread: Speedomeer help?

  1. #16
    Join Date
    Jan 2010
    Location
    Bossier City, LA
    Posts
    2,310
    Quote Originally Posted by yayo_ayala View Post
    I have a similar situation. My odometer is working but the speedometer is not working. Today I replaced the VSS, it is located in the rear part of the transmission on the driver side. Is there a way to test the cable? Probably lifting the rear tires and running the engine, I am looking for troubleshooting options.

    Thanks


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    Think about it.

    BOTH the odometer and speedometer are driven by the VSS; if one works, the signal is getting to the speedometer module.

    So there's a problem inside the module if one works and the other does not.

    You could raise the rear end and run it. Or you could fake the VSS with a signal generator - the VSS outputs 8,000 pulses per mile, so you take the MPH, divide that by 3600, and multiply THAT by your desired speed, and get your frequency.

    I've done some ballpark numbers for you, though.

    60Hz is 27 MPH.

    120Hz is 54 MPH.

    240Hz is 108MPH.

    And if you have the 145MPH speedometer, 300Hz is 135MPH.

    You can inject that at 5V+ at the VSS connector, and the speedometer and odometer will spin up like you're travelling that speed.

    Don't have a signal generator? Don't blame you until now. Just as one possible source, https://www.mpja.com/Variable-Freque...info/35478+TE/ is $9 plus shipping, will run off the car's 12V electrical system, and will do the job. It's cheap, but eh. Set for a 50% duty cycle square wave, and you're golden.

    RwP

    EDIT 2: You DID swap the drive gear, right?
    Last edited by RalphP; 04-26-2020 at 10:22 PM. Reason: Fixed description. Asked question.

  2. #17
    Join Date
    Jul 2017
    Location
    Northern Virginia
    Posts
    56

    Probably bad speedo

    Quote Originally Posted by yayo_ayala View Post
    I have a similar situation. My odometer is working but the speedometer is not working. Today I replaced the VSS, it is located in the rear part of the transmission on the driver side. Is there a way to test the cable? Probably lifting the rear tires and running the engine, I am looking for troubleshooting options.
    I had the same issue. My speedometer went dead while I was driving the car. I stopped and restarted the car and it died for good after a brief flash of life. I considered the VSS, but since the odometer was still working and was accurate per the mile markers on the road it had to be something else. It could be the circuit, but a bad speedo is more likely. I had a replacement cluster for a different fix. When I put in that speedo it worked but the odometer was dead. I ended up buying a 140 mph speedo from Super Coupe Performance Parts with the replacement gears and everything is good now. I even got "lucky" and the new odometer pretty much matched the existing mileage.

    MP

  3. #18
    Join Date
    Dec 2016
    Location
    Dallas
    Posts
    120
    Thanks guys, yes it was the speedometer. I took it to a shop here in Dallas (Zepco Speedometer Repair) and they tested it and determined that it was the speedometer and replaced it. The speedometer is working fine, but my cruse control still not working.

    PD.- I might need to go once again to Zepco, the high bind indicator is not working.
    Last edited by yayo_ayala; 05-20-2020 at 11:55 PM.

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