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  1. #1
    Join Date
    Oct 2014
    Location
    United Kingdom
    Age
    49
    Posts
    279

    Smiths Speedo Stopped Working

    Ok so I have my first ever fault with my Dax - driving home at the weekend and noticed that the speedo was not working It had been working when I set off. It's your standard Smiths 180mph with Black face.

    Now I won't get chance to have a look until this weekend at the earliest so thought I would reach out to you first with any suggestions to focus my investigation.

    Clearly I need to check the rear connections of the Speedo but the mileage is still showing so assume we still have power etc.

    I don't know whether the gauges are mechanical or electrical but presume there is some connection/sensor to the gearbox which I need to check - any photos appreciated so I know exactly where to look.

    Anyone else had a similar problem and what was the cause or any other suggestions welcome.

  2. #2
    Join Date
    Feb 2007
    Location
    West Sussex
    Posts
    7,663
    ...is there a speedo drive cable in the back? Its a black cable about 8-10mm in diameter. If so,then its mechanical, so suggest yo send to Richfield Speedograph.

    Have you got an LED or other electrical/digital type display - if so, its an electronic one.
    Last edited by KevinW; 17-07-17 at 07:33 PM.
    Crendon Chassis No.49
    Huddart FE428 + toploader

    Not listed in the Shelby Register.

  3. #3
    Join Date
    Apr 2004
    Location
    East Leake, Nottinghamshire, England.
    Age
    53
    Posts
    9,137
    If it's run off magnets on the prop flange then perhaps they might of come off?
    Martin

    351W 416.7 HP and 466.8 ft-lbs

    Running Mega Squirt and Edis 8


  4. #4
    Join Date
    Nov 2016
    Location
    Cheshire
    Age
    56
    Posts
    55
    Quote Originally Posted by david.mt View Post
    Ok so I have my first ever fault with my Dax - driving home at the weekend and noticed that the speedo was not working It had been working when I set off. It's your standard Smiths 180mph with Black face.

    Now I won't get chance to have a look until this weekend at the earliest so thought I would reach out to you first with any suggestions to focus my investigation.

    Clearly I need to check the rear connections of the Speedo but the mileage is still showing so assume we still have power etc.

    I don't know whether the gauges are mechanical or electrical but presume there is some connection/sensor to the gearbox which I need to check - any photos appreciated so I know exactly where to look.

    Anyone else had a similar problem and what was the cause or any other suggestions welcome.
    If it's an electrical (digital mileage readout) then I get that regularly.
    Tracked it down to the sensor being incredibly sensitive to distance to the magnets on the drive shaft.
    If I drive hard it seems to vibrate the sensor away from the shaft and I lose the readings until it works it's way back.

    It's not loose (spent far too much time underneath the car tracking this down), so I've learnt to live with it on the occasions it happens, until I get chance to reset the whole kaboodle

  5. #5
    Join Date
    Apr 2004
    Location
    East Leake, Nottinghamshire, England.
    Age
    53
    Posts
    9,137
    Had problems with mine but in the end it turned out the magnets were too close and once moved further away it has worked perfectly ever since.
    Martin

    351W 416.7 HP and 466.8 ft-lbs

    Running Mega Squirt and Edis 8


  6. #6
    Join Date
    Oct 2014
    Location
    United Kingdom
    Age
    49
    Posts
    279
    Quote Originally Posted by keirik View Post
    If it's an electrical (digital mileage readout) then I get that regularly.
    Tracked it down to the sensor being incredibly sensitive to distance to the magnets on the drive shaft.
    If I drive hard it seems to vibrate the sensor away from the shaft and I lose the readings until it works it's way back.

    It's not loose (spent far too much time underneath the car tracking this down), so I've learnt to live with it on the occasions it happens, until I get chance to reset the whole kaboodle
    We have a winner - car back in the garage - had a good look. Nothing obvious so went out again and working fine!. Must have the same issue that with some spirited driving or heat the sensor looses communication with the magnets and speedo stops working. Will have another look and see if anything is loose or just put it down to TADTS.

    Thanks for the suggestions.

  7. #7
    Join Date
    Oct 2014
    Location
    United Kingdom
    Age
    49
    Posts
    279
    Ok car up on ramp and everything solid with sensor setup - should I leave or try and reduce the gap a little between sensor and collar?

    Attached Images Attached Images

  8. #8
    Join Date
    Jul 2014
    Location
    Southam, Warwickshire
    Age
    54
    Posts
    233
    Hi dave.mt,

    We use similar speed sensors as this at work. The gap between the sensor and the target is very important. Have you got a data sheet for your sensor? This should give you the desired gap. If not, a trawl on google will probably furnish you with the necessary information assuming you have the part number etc. for your sensor.

    Hope this helps.

    Cheers,
    Stu
    AK427 Gen III, Ford 347, TKO600
    Build Blog:- stu238-ak427.blogspot.co.uk

  9. #9
    Join Date
    Oct 2014
    Location
    United Kingdom
    Age
    49
    Posts
    279
    Hi Stu - thanks for the info.

    No data sheet but a Google search suggested that the sensor to collar gap should only be 0.80 to 0.100 (I assume inches!). Also the joins in the collar should only be around 0.030 - one of mine is clearly larger so I may have a fiddle .

  10. #10
    Join Date
    Jul 2014
    Location
    Southam, Warwickshire
    Age
    54
    Posts
    233
    Quote Originally Posted by david.mt View Post
    Hi Stu - thanks for the info.

    No data sheet but a Google search suggested that the sensor to collar gap should only be 0.80 to 0.100 (I assume inches!). Also the joins in the collar should only be around 0.030 - one of mine is clearly larger so I may have a fiddle .
    Hi, I would suggest that this is in millimeters, not inches. Even 0.1 inches seems a big gap to me. We typically use around 1mm clearance. Might be worth checking just to make sure.

    Cheers,
    Stu
    AK427 Gen III, Ford 347, TKO600
    Build Blog:- stu238-ak427.blogspot.co.uk

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