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  1. #1

    Default speedometer cable and speed sensor

    I am replacing my speedometer cable and I have the speed sensor on my 85 going into the transmission. Can I do away with the speed sensor and just use a non cruise control cable?

    Thanks
    Brant

  2. #2
    FEP Super Member erratic50's Avatar
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    Do you have CFI or a carb? Automatic or manual?

    i believe the CFI systems use vehicle speed as an input to avoid stalling. They throw codes and stall at lights if I am not mistaken.

  3. #3

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    Sorry, yeah, manual carbureted. I just was unsure if I got the cable for a non speed sensor if the end plugs into the transmission like the speed sensor does currently.

    Thanks
    Bramt

  4. #4
    FEP Super Member xctasy's Avatar
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    Quote Originally Posted by RazorbackGT View Post
    Sorry, yeah, manual carbureted. I just was unsure if I got the cable for a non speed sensor if the end plugs into the transmission like the speed sensor does currently.

    Thanks
    Bramt

    Shouldn't have anything other than a stock speed cable knurled steel end that slots in the transmission. If its a later gearbox, it mighat have another VSS connection.


    There are a few different cable types.

    My car didn't have Cruise, but it did have the cruise control cable like this....



    Its on the speedo shaft drive, and is an old part dating back to the 1969 Distro-Vac emissions timing device from the October 1969 1970 Model year CA emissions 351C's.


    It was then used for years to run the Cruise control, but has been a standard fitting on lots of Fox, Cruse optioned, or not.

    It has variable reluctance, and drops off the voltage to run an electronic speedo at about 6 mph or so.







    There are 12 V replacements for other applications that read right to through to zero Zimmer walking frame speed.



    This is the sending unit for the Autometer Electronic Speedometer (Ford specific). It just plugs right in place of the mechanical one, and then just wire up to the new speedo. The Speedo has to be calibrated once installed but that's as easy as driving two miles. Autometer sends very clear instructions and has a video on their web site. The new speedometer is way more accurate then the old Ford one and can be recalibrated for new tire sizes or other changes that wreak havoc on a mechanical speedo

    Here is how it workes when pinned...


    Quote Originally Posted by xctasy View Post
    What a very strange, but very cool system.. It's just the 8000 plips per mile, early EECIV compatibale 8 pulse per revolution VRS system, with a variable voltage sqaure wave form from 20 mph onwards. It does have some funny features on sub 20 mph voltage polling, technically able to poll back down to 7 mph in some circumstances.

    Certain versions of the EEC III, EEC IV and most EEC V's require an 8000 pulse per mile vehicle speed sensor signal from the PSOM (speedo module), which is just like all other EEC-IV equipped vehicles

    Other later EEC V applications use a 16000 or 40000 pulse per mile VSS signal.



    I'm told that some of the CFI or Speed Desnity AOD Fox varaints poll down to 7 mph, and allow idle speed conditioning.



    Sadly, the periodic zero moh to 19.9 mph null readings won't do what I need it to do, as like some ABS circuits, it has no reliable squarewave below 20 mph to log distance travelled. Its circumstantial, and as such, presnts a Major Bummmer.....

    I could probably use a prescaler to create a digital sqaure wave form from an SN95 hub, but I can get another Proximity sensor tommorw in the post for 95 US.


    I jacked up my car, and ran the standard Hetz, A/C Voltage and Ohms resistance checks from zero to 62 mph, with my metric speedo registering in KM/H. Note that there is no voltage going up to 32 km/h or 20 mph, but once invoked, the voltage can be recorded right donw to zero, so there is an interesting voltage speed, Hertz resolution

    0 km/h, 0 mph 0 Hz, zero volts AC
    12 km/h, 7.4 mph, but 0.016 volts AC on over run
    See picture

    20 km/h, 12.4 mph 0 Hz, zero volts AC
    30 km/h, 18.6 mph 0 Hz, zero volts AC, but 0.033 volts AC on overun
    See picture

    32 km/h, 19.9 mph 0 Hz, 0.00 volts AC
    32.2 km/h, 20.0 mph, 0 Hz, 0.019 volts AC
    40 km/h, 24.9 mph 0.056 volts AC
    50 km/h, 31.1 mph, 0.083 volts AC
    60 km/h, 37.3 mph 102 Hz, 0.109 volts AC
    70 km/h, 43.5 mph, 0.149 volts AC
    80 km/h, 49.7 mph 0.186 volts AC
    88 km/h, 54.7 mph 125 Hz, 0.223 volts AC
    See picture

    100 km/h 62.1 mph, 0.273 volts AC
    See picture



    The square wave form kicks in after 19.9 mph on the upward rise, with zero Hertz cycles per second on my Cat IV multimetervoltage and the voltage increasing steadily from 20 mph on upwards.


    The on the decilne after 20 mph, it records right down to 7 mph, assumably for the one Speed Density AOD car that needed idle speed control...

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