Mk3 no speedo/ wonky fuel gauge.

Discussion in 'Electrical' started by Pete17, May 23, 2020.

  1. Pete17 New Member

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    Hi,

    Encountered a new problem...
    Started up my mk3 golf 16v and the speedo is completely inop and the fuel gauge moves erratically across full to half tank...
    No previous problems so must be linked I'm guessing.
    All fuses seem fine.
    Checked the speedo connector and it has a good earth but no ign live on.
    So can anyone tell me where the speedo gets its live from?
    Seems to be a known problem but cant find solutions...
    Thanks.


    Just looked at fusebox FAQ and found that pin 1 at speedo sensor is fed from D8 which is suspicious as i just replaced ignition switch( same circuit). Maybe a dodgy wire ....
     
    Last edited: May 23, 2020
  2. rubjonny

    rubjonny Administrator Admin

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    mk3 speedometer is fed from the coil live G1/4, not sure why I had it to D/8 as well in my guide I guess some random american diagram showed it there or something, fixed now anyway.

    have a look at the brown/white cluster earth from G1/5 to the side of the head, this feeds dash and fuel level sender so could be the cause of your issues :)
     
    Pete17 likes this.
  3. Pete17 New Member

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    So just had another wee look and the earth is ok at cylinder headand earth is good at speedo sender connector.

    Ign live on G1/4 is ok ( and obviously at coil as it starts) but no ign live at speedo connector. Is there another connector/crimp connection or something?
    Is it just the speedo sensor, coil and ecu pin 38 it feeds?
    Thanks
     
  4. rubjonny

    rubjonny Administrator Admin

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    on the abf g1/4 feeds the coil and speedometer only, pin 38 is for vr6 ecu only :)

    theres a wire joint somewhere along the G1/4 wire, maybe look for alarm or immobiliser install perhaps they messed with this crimp joint. the wire goes through the round plug pin 5, worth checking here for voltage as well in case break is on engine side. the earth for the speedometer sender goes to the side of the head as well with the dash earth
     
  5. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    MK3 Speedo 1.JPG MK3 Speedo 2.JPG
    On a MK3 Golf, if you lose the speedo signal into the cluster, the MPG calculation is messed up and the fuel gauge will begin to show symptoms as described.
    I have had this with my old MK3 VR6 when the runaround pump, leaked hot coolant on the speedo sensor below, rendering it inoperative and my fuel level reading went from 1/4 to half.

    I have found MK3 electrics quite robust to wires falling apart. However above shows the current flow path for the speedo sensor G22.

    You should have ignition live at pin 1, with the key on. If you do, then your sensor has failed.

    .
     
    Last edited: May 28, 2020

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