Speed Sensor update | Page 2 | FerrariChat

Speed Sensor update

Discussion in '308/328' started by Rich in Panama City, Apr 3, 2015.

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  1. mwr4440

    mwr4440 Five Time F1 World Champ
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    Jun 8, 2007
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    Mark W.R.
  2. mwr4440

    mwr4440 Five Time F1 World Champ
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    #27 mwr4440, Jun 18, 2019
    Last edited: Jun 18, 2019
    Question: is there a difference between MPH Speedo/Odo cars and KPH Speedo/Odo car's SENSORS of the same year?

    Would say a 1981 GTSi with an OEM fitted MPH Speedo/Odo, have a different sensor from a 1981 GTSi with a OEM fitted KPH Speedo/Odo?

    I once put a KPH Speedo in my MPH car and it didn't work properly.

    Is the difference in the Sensor or the Speedo unit itself?
     
  3. Brian A

    Brian A F1 Rookie

    Dec 21, 2012
    3,079
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    1983 US 308 GTS QV
    I received my sender board in the mail today!

    The board is tiny! (What did I expect?)

    Will report back after I install and test (which is after I get my darned valve covers back on and the engine back together).

    Look forward (hopefully) to finally having a speedometer that is reliable and doesn't require frequent replacement of the $280 sender!

    … love the post office's new high tech way of cancelling stamps!

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  4. alhbln

    alhbln Formula 3
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    Mar 4, 2008
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    Adrian
    Only difference between mph and kph of same type (1 or 2/3) is the faceplate and a different gear part inside the Speedo for the ODO.
    The sensors itself are independent of mph or kmh versions.
     
  5. mwr4440

    mwr4440 Five Time F1 World Champ
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    Ok.

    Any Idea why my KPH Speedo didnt seem to work properly?

    Seemed to 'read' way too fast.

    Both Speed and ODO.



    Or, am I ..... "seein' things?"
     
  6. alhbln

    alhbln Formula 3
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    Mar 4, 2008
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    Adrian
    The speedo sensor is always the same (Type 1 or Type 2, requires the matching Speedo), but the Speedos itself are different between kmh and mph (different gear inside the Speedo), and there are different Speedo PCBs to cater for normal aspirated cars as well as turbo cars which have a different trigger wheel in the gearbox.
    If you have the correct gearbox/sensor setup and the factory Speedo then everything should be fine. Difference of speed by the factor 2x would indicate the wrong sensor/gearbox and Speedo configuration. Difference of 1.6x is a wrong Speedo gear/faceplate combination.

    The different sensors are documented here:
    http://www.dinoplex.org/instruments/vegliaspeedosensor/index.html

    If you want to you could ship me your Speedo for a test run on the bench to check the displayed speed and configuration.
     
  7. Brian A

    Brian A F1 Rookie

    Dec 21, 2012
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    I hope to install my board in a few weeks when I have the car back up on jack stands.

    Regarding the "potting" process, is there any specific epoxy that is best? I also notice on the other thread that Adrian questions using "PU compound" rather than epoxy.

    If you could post a link to Amazon for the recommended potting product I would appreciate it since it eliminates lack of clarity. I have never bought a product like this before.
     
  8. alhbln

    alhbln Formula 3
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    I have used PU (Polyurethane) potting compound for electronics quite often with very good results, but there is no problem with using epoxy resin for the potting.

    With epoxy resin try to avoid the super fast "5 minute epoxy" as it might be difficult to process if you don't have the routine to work with epoxy. Industry grade epoxy usually cures within 24 hours at room temperature but there is also express epoxy which cures within 30 minutes. If you raise the outside temperature by using an oven the epoxy will cure much faster. The epoxy/hardener bottle sizes at Amazon are quite large, maybe you can find something smaller/cheaper at a local hardware store?

    Polyurethane potting, example:
    https://www.amazon.com/MG-Chemicals-Urethane-Potting-Compound/dp/B07R18G154/

    Epoxy resin potting, example
    https://www.amazon.com/Epoxyseal-Electronic-Grade-Potting-Epoxy/dp/B00VXV9YZ2/
     
  9. Brian A

    Brian A F1 Rookie

    Dec 21, 2012
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    Thank you for the detailed reply. It has the exact information I need.
     
  10. Brian A

    Brian A F1 Rookie

    Dec 21, 2012
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  11. SJD007

    SJD007 Rookie

    Jun 6, 2021
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    Simon Dean

    Thanks for the good advice - mine appears to be reading roughly twice what it should. MPH speedo type 2 (round indicator lights) that says 60 mph when i give it 110 hz signal. I’ll need to check if it’s 1.6x or 2x when I’m driving. I was wondering how a sender could consistently double the speed. I’ve got the type 2 sender mounted underneath so “should” be the correct match. Maybe someone put in the wrong faceplate some time. I’ll check that before pulling the sender.
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  12. alhbln

    alhbln Formula 3
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    As always with Marelli/Veglia, there are some exceptions to the triangle/round indicator rule as Speedos inbetween the change to the new internals often had both type of faceplate mixed. A nearly faultproof indicator is the movement of the ODO, if it steps (jumps) then the internals are a Type 1 speedo. If the ODO moves the number wheels smoothly, then it is a Type 2 speedo.

    110 Hz resulting in 60 mph display is a Type 1 speedo. This would explaion the double speed, you got a Type 2 sender (sending 220Hz for 60 mph) mixed with a Type 1 Speedo.
     
  13. SJD007

    SJD007 Rookie

    Jun 6, 2021
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    Simon Dean
    I was so close to ordering a sender but couldn’t quite figure how it could double the output. Thank you! I’ll go for a drive and check the odo for confirmation before sourcing a speedo. I hadn’t checked that odo thing thinking the round indicator lights was proof type 2. Wow. Things really got mixed up early 80s huh. Type 1 speedo in disguise would explain this nicely! I did try a converter but it doesn’t recognise the signal (I might try a 560R resistor across the signal to ground - I’m getting 12v no load at the signal wire at the instrument cluster?). Anyway, looks like swapping out the speedo best option. Thanks again :) great advice!
     
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  14. SJD007

    SJD007 Rookie

    Jun 6, 2021
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    Simon Dean
    And the plot thickens… my speedo has smooth rolling Odo. I found a sticker on the side… does this make sense to anyone?
    I fed it 220Hz and it went to 120mph.
    I used the freq on my multimeter and got about 100hz from the sender doing (roughly) 25mph just guessing (my speedo not helpful ha ha!).
    Next I’m going for a drive with my oscilloscope to see what waveform is coming out of the sender and see if it’s clean. Is there a possibility the speedo has been “fixed” with the wrong chip or something? I’m actually trying to get my speedo adapter to function after finding out how much a kph speedo costs! $46 for a speed adapter a lot cheaper but still won’t recognise the sender signal either straight from the wire or with a resistor across it to ground (or with it plugged into the speedo). It can convert the signal from my square wave generator nicely and that in turn will trigger the speedo, and the speedo recognises the sender signal lol.

    I’ll post pics of the speedo sticker, 220Hz giving 120mph, 96Hz from sender doing about 25mph, the converter in action loving my square wave generator (but ignoring the sender signal) running at 50%, and my car just because :)

    Do I need to open my speedo and see if it has been interfered with?? Lol


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  15. alhbln

    alhbln Formula 3
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    Mar 4, 2008
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    Based on the Veglia label this is indeed a Type 1 speedo, at that build date there were both triangular and round side indicators used. With this type the ODO numbers should move in small steps (not jump from one number to the next, i might have explained that not correctly). It takes about ten steps to move from one number to the next for the rightmost number. The Type 2 ODO moves absolutely smooth without small steps.

    The speedo sensor signal is a bit special, having the voltage supply on the signal wires. I don't know of any Speedo converter that is compatible with this kind of signal, unfortunately.
     
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  16. Lawrence Coppari

    Lawrence Coppari Formula 3

    Apr 29, 2002
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    Lawrence A. Coppari
    Most of us don't have a milling machine but you can get the sensor apart by lightly clamping it at the hex in a vise. Remove the crimp metal with a hacksaw by gently sawing around its circumference. Beneath that is a steel washer you can pick out. Then pick out the rubber O ring with a dental pick. Gently push the innards out. You can loosen it up first by gently twisting at the end where the wires are. The plastic there is fairly sturdy. My old one failed so I decided to see if I could get it apart without damaging it. It is not difficult.
     
  17. SJD007

    SJD007 Rookie

    Jun 6, 2021
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    Simon Dean
    Hi so this could be helpful as I’ve managed to get a speedo adjuster to work for me. With the great info on this forum (thank you again Adrian!) I checked the signal from my sender at the harness behind the instrument cluster. I only got a signal when adding a 560R resistor to ground across the red/blk wire coming from the sender. Then it was perfect - see my cheap oscilloscope trace! My first speedo adjuster (from Jaycar in NZ $46) would intermittently recognise the signal, and then (with some considerable lag) send the reduced pulse signal to the speedo. My speedo (originally reading twice the speed) was so laggy with this unit it was unusable.

    Rather than buy another speedo I bought a speedo adjuster with better reviews (Dakota Digital SGI-100BT $NZ180 ) from Amazon, it arrived in a week, and hooked it up. I had already popped the individual sender red/blk connectors (easy with a small flat blade screwdriver) out of their respective multi plugs behind the cluster with the steering wheel still in place and so it was easy to extend this to behind the stereo where there is switched power.
    The Dakota device runs off Bluetooth so I could send a test signal to the speedo (it worked - see pic) and the the 560R across ground and the signal at the Dakota module it sensed the sender signal nicely and I could calibrate the speedo with the app. It didn’t work without the resistor (see pic) - it’s internal pullup didn’t help so I guess this is pulldown. That seemed to be the trick to get it to work.
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