Speedo sender unit interchangability

Discussion in 'General Motoring' started by John Robertson, Dec 31, 2004.

  1. HI ALL how does the Speedo work by impulse or mechanical means .Can you alter the reading of the cars speed by replacing a sedans Speedo module on the differential with one from a wagon .Or are they the same ?
    I have a 740 turbo with 205 -55-16 tyres or tires and would like to go to 225-60- 16 a more common size here and cheaper .My Wife has 195-60-15 on her 740 turbo could we go 205-60-15 a much cheaper tyre tire to buy , using the sender unit on the back axle .We love our Volvos so we got our son a 1990 240 to learn on and boy its fun to drive ,with 195-70--14 tyres .
    Same question again is 205 or 215 -60-14 a reasonable conversion using the rear diff sender .Thanks from down under where the water flows the other way or does it ?
     
    John Robertson, Dec 31, 2004
    #1
  2. John Robertson

    James Sweet Guest

    alter the reading of the cars speed by replacing a sedans >Speedo module on
    the differential with one from a wagon .Or are they the same ?
    225-60- 16 a more common size here and cheaper .My Wife has >195-60-15 on
    her 740 turbo could we go 205-60-15 a much cheaper tyre tire to buy , using
    the sender unit on the back axle .We love our >Volvos so we got our son a
    1990 240 to learn on and boy its fun to drive ,with 195-70--14 tyres .
    rear diff sender .Thanks from down under where the water >flows the other
    way or does it ?


    All 700 series cars use an electronic speedo with a sensor in the rear axel
    unit. The sensor is the same, but the calibration of the speedometer varies
    with tire size. 240's used a mechanical cable speedo until '85, after that
    they got the same electronic setup as the 700's.
     
    James Sweet, Dec 31, 2004
    #2
  3. thanks.. so that means that the speedo can be adjusted by the sensor type ?
     
    John Robertson, Jan 1, 2005
    #3
  4. I wouldn't think so. Typically reluctor sensors are just a winding on a
    magnetized core, and they count the number of teeth that go by. A new sensor
    could change the output level but can't change the rate.

    Mike
     
    Michael Pardee, Jan 1, 2005
    #4
  5. John Robertson

    James Sweet Guest

    ?


    No, the calibration is in the speedo itself, I haven't looked into the
    details though, it might have a potentiometer you can adjust, or it might
    use soldered or plugged jumpers, you'd have to check.
     
    James Sweet, Jan 1, 2005
    #5
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