No rev counter or fuel gauge?

Discussion in 'Electrical' started by PhilRyder, Sep 22, 2023.

  1. PhilRyder

    PhilRyder Paid Member Paid Member

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    As mentioned in my engine transplant thread.
    We have removed the binnacle and since then the rev counter and the fuel gauge are not working. The temperature gauge which is in the other dial works fine. This makes me think it is a problem with the dial? Should there be an earth or similar which may have been dislodged?
    Any ideas or previous experience would be gratefully received.
     
  2. PhilRyder

    PhilRyder Paid Member Paid Member

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    Does anyone know if @NateS2 is still about and repairing clocks? Last seen here in July so not long ago.
     
  3. daNpy Forum Member

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    The tacho and the gauge are separated dials. The gauge can be removed from the tacho and they do not share a direct (electrical) line.
    As far as i know the gauges are fed from the voltage regulator in order to be able to measure correctly. The tacho isn't.

    It is strange that both of them are failing.

    IMG20211003151245.jpg
     
  4. PhilRyder

    PhilRyder Paid Member Paid Member

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    Yes, agreed, it is odd.
    Ralph took it all apart last night and the fuel gauge responds when given 12v. Is there a way of testing the rev counter on the bench?
    Also, we fitted a spare binnacle (no rev counter unfortunately) and the fuel doesn’t work on that either. This points to a wiring issue.
     
  5. daNpy Forum Member

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    What kind of signal were you feeding with in the car? From ECU or the coil?

    If I remember correctly it's just 12v, gnd, input a fourth connection which is unclear to me and not necessary to test the tacho. You'll need a 80V signal by the way.
     
  6. PhilRyder

    PhilRyder Paid Member Paid Member

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    ECU. This is VR6 R32 don’t forget. There is a 6 cylinder to 4 cylinder converter as well.
     
  7. daNpy Forum Member

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    Ah yes then you'll need the signal amplifier
     
  8. dodgy

    dodgy Paid Member Paid Member

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    Check the ground at tank plug, I'd lost one of the 2 on mine when fitted mk3 tank, just bridged it from the other one .
    It's a 4 wire loom, 2 for pump, 2 for the gauge sender which is negative feed and then return to clocks.
     
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  9. PhilRyder

    PhilRyder Paid Member Paid Member

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    Will check carefully tomorrow.
     
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  10. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    For the rev counter you need James to have a look as I believe he made the loom.
    Not sure what clocks you are using and too lazy to re read the post.
     
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  11. PhilRyder

    PhilRyder Paid Member Paid Member

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    If we cannot resolve the rev counter James will come and have a look.
    The clocks are non MFA VDO MK2 CE2
     
  12. PhilRyder

    PhilRyder Paid Member Paid Member

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    Right then, testing the plug at the fuel tank. All these tests I have done with the battery negative disconnected.
    The two outside pins are for the fuel pump. The pump works fine. However, when I test continuity between each pin and earth (body of the car) I get a reading? I thought I would only get a reading from the earth wire (brown)?
    Testing continuity for the two inner connections (fuel sender) I get a reading from the violet/black wire but not the brown/blue wire. Is this correct?
     
  13. PhilRyder

    PhilRyder Paid Member Paid Member

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    All four wires have continuity plug to plug.
     
  14. afbiker02

    afbiker02 Paid Member Paid Member

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    Sorry to ask a random question on your thread Phil but what is the wire going to the bulbs for? I only ask because when I changed my bulbs and gauge faces recently i broke the ribbon and now my normal dash lights don't work.
     
  15. daNpy Forum Member

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    Normal dash lights? You mean the bulbs in the cockpit unit itself right, to illuminate the dials?
    Is the connector for the headlights connected OK? There is a dial to set the intensity. What happens if you rotate that one?

    Edit: I now see you refer to the wire on my unit. That is made by a previous owner. It's just the cockpit lights.
     
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  16. daNpy Forum Member

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    Sorry to say this but I expect you'll need an amplifier as the ECU gives out a 12V block signal and the tacho needs a spike of a higher voltage. In other words it won't be in the wiring loom then ;)
    You can test the tacho by wiring it up to a single-coil engine and providing 12V to it, it's relatively easy :)
     
  17. PhilRyder

    PhilRyder Paid Member Paid Member

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    More testing.
    Both gauges respond when 12v is put across the nuts on the rear.
    Using a voltmeter, positive to rear of gauge and earth to car body a reading of 10.3v is seen. The same when the other rear nut is used.
    Using a voltmeter across the two nuts zero volts is seen.
    Ign on and one rear nut connected to car body earth gauge responds but this is full earth (rather than reduced from the sender) so a full tank reading is seen.
     
  18. PhilRyder

    PhilRyder Paid Member Paid Member

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    So the solution?
    Well @dodgy was correct all along (as usual :lol:).
    It seems that the earth from the fusebox, being the blue and brown, was indeed broken. It seems somewhere at the fusebox it had stopped doing its job. Careful jumping of the brown and the blue/brown at the plug at the tank made the gauge work correctly.
    The solution was to join the brown and blue/brown at the tank end (could be anywhere along that piece of loom really) et voila :clap:
    Zoom in and you will see where I bared the cables. I then soldered them together at that point.
    IMG_1976.jpeg
    Really though, I need to know where the fault is at the fusebox………..
     
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  19. PhilRyder

    PhilRyder Paid Member Paid Member

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    There is an amplifier/converter (6 cylinder to 4 for the mk2 rev counter) wired in by James. Hopefully he will come and have a look this week and solve the problem. I actually hope it is something so simple it makes us look stupid for not seeing it :lol:
     
  20. dodgy

    dodgy Paid Member Paid Member

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    Glad I could be of help, and it was able to be fixed.
    I can grab the fusebox as a spare if it's still there in couple weeks time, there's a lot of brass strips inside that can corrode over 30 years, so could be something like that or a broken wire in the sub loom to boot like mine had.

    Mates bmw saloon did it to the boot lock loom and trying to get that to trigger via the rear seats outside my house was interesting to say the least.
     
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