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Thread: Bad Earth???

  1. #11
    Join Date
    Aug 2011
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    East Sussex
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    15,858
    Sean. Sounds like a high resistance in the ign fed positive side if you can make it go away by powering from another source. Either (and would have thought others would have the same problem) the cable is not man enough that feeds the ign circuits of the fuse box. OR Are you still using the original Sierra Ign Switch? If so the Ford connector on the short loom of switch wires are renowned for the connectors breaking down! Worth a wiggle
    Chris
    Ex AK427 351Cleveland T5WC

  2. #12
    Join Date
    Feb 2007
    Location
    Billericay, Essex, England.
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    805

    Red face

    Chris,

    Not using the Sierra switch but an original Lucas one - just doing some tests around here as it is possible that may be the problem. Either way, I'm getting closer to a fix hopefully!

    I agree with you regarding others would be having the same problem - if they have noticed would be another matter, as I didn't!

    Sean
    Too many idiots, not enough villages!

  3. #13
    Join Date
    Feb 2007
    Location
    Billericay, Essex, England.
    Posts
    805
    Ignition switch seems fine -

    So I'm assuming it's the feed to the ignition switch as putting in a heavy duty cable in place of the thin cables supplied as part of the loom makes no difference either.

    Strangely enough (or maybe not so) with all this unconnecting and reconnecting of wires the situation seems to have improved to the extent that it is hardly noticeable.
    I'm now wondering if it was just some light corrosion on some terminals as I haven't been using the car anywhere near as much as I should over the winter???

    Is that likely?

    Do we have a "pulling hair out" smiley???

    Sean
    Too many idiots, not enough villages!

  4. #14
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    Light corrosion or maybe a dodgy crimp is certainly a possibility.

    Best I can manage on the smiley
    Chris
    Ex AK427 351Cleveland T5WC

  5. #15
    Join Date
    Feb 2003
    Location
    Honiton, Devon
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    52
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    7,710
    Sean, sounds like you've nearly fixed it anyway, but.....
    if you get hold of a battery conditioner/charger, you could do your testing with it connected to the battery instead of running the car.
    Assuming you're not checking the charging sid eof course.
    2003 Dave Brookes Dax 350ci Chevy SB.
    2008 Crendon 462ci Ford Sideoiler FE Chassis No.43
    2012 Crendon 351ci Ford Cleveland Chassis No.24
    2014 Crendon 452ci Ford FE Chassis No.66 (in progress)

  6. #16
    Join Date
    Feb 2007
    Location
    Billericay, Essex, England.
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    805

    Talking

    Thanks Neil, good idea!

    Anyway - I have now bypassed everything with heavier cable to eliminate EVERYTHING.

    and put it all back as it was and it seems to be near as damn it perfect.

    Now, if I turn the lights off in the garage, close the garage doors, so it is pitch black in the garage, I can't see any dimming of the brake lights at all. But if I cup my hands around the tail light and put my eye up against my hands (I know some of you are laughing at this image!) I can very faintly see a very very slight flicker at the beginning of each click of the indicator (I think emphasized in my head by the clicking noise making me think it is dimming also).

    So, I think that's good enough for me. As I have now eliminated everything I think I can say that it is normal and it must have been a poor connection somewhere in the system that I have found without realising it.

    Thanks to all those that helped.

    Roll on evening driving around LeMans!!!

    Sean
    Too many idiots, not enough villages!

  7. #17
    Join Date
    Aug 2011
    Location
    East Sussex
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    Gumpace

    You can be the Pace Car with all your lights flashing at once
    Chris
    Ex AK427 351Cleveland T5WC

  8. #18
    Join Date
    Feb 2007
    Location
    Billericay, Essex, England.
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    Talking

    In that case I'd better put some dirt back in all the terminals!
    Too many idiots, not enough villages!

  9. #19
    Join Date
    Feb 2007
    Location
    Billericay, Essex, England.
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    805
    Hi all,

    Resurrecting an old thread of mine here but I've never been convinced that I fixed this issue so.....

    I've done some testing centred around the rear lights and made some odd discoveries (well I think so, anyway).

    Checking ohms between earth at rear light and earth at battery is 0.8 ohms (so, assume good),

    However, ohms between +ve at rear lights and earth at battery is showing a reading - shouldn't this be an open circuit and therefore zero ohms???


    Readings as follows (hopefully to help diagnose) -

    WHEN SIDE LIGHTS ARE OFF (remembering all these readings are at the rear lights) -

    Resistance between +ve at turn light and earth is 2.5 ohms

    Resistance between +ve at rear light and earth is 1.7 ohms

    Resistance between +ve at brake light and earth is 1.5 ohms


    WHEN SIDE LIGHTS ARE ON (remembering all these readings are at the rear lights) -

    Resistance between +ve at turn light and earth is 13.5 ohms

    Resistance between +ve at rear light and earth is 0 ohms

    Resistance between +ve at brake light and earth is 45.0 ohms


    WHEN HEAD LIGHTS ARE ON (remembering all these readings are at the rear lights) -

    Resistance between +ve at turn light and earth is 183.0 ohms

    Resistance between +ve at rear light and earth is 0 ohms

    Resistance between +ve at brake light and earth is 50.0 ohms


    Switching hazards on reduces resistance at turn light +ve and earth to 0 ohms - (I'm going to assume this may also happen with the brake lights but I've got no one available to press the pedal!).

    Hope this makes sense (?).

    Have I got a short circuit somewhere?

    Everything seems to work ok except fuel gauge goes up and down slightly with the hazards and up when the heater is turned on.

    Any ideas where to look. I'm close to pulling the loom out and starting again. Car has been on the road for nearly 20 years so reluctant to pull too much out but we can't help tinkering can we!

    Many thanks in advance.

    Sean
    Too many idiots, not enough villages!

  10. #20
    Join Date
    Feb 2008
    Location
    Rayleigh Essex
    Posts
    10
    Typical symptoms of a bad earth. Also faulty light units can cause this problem, if the bulb(s) are not making a good earth contact through the bulb holder. Normally on the rear loom all the earths end in one or two ring terminals bolted to the chassis/frame. Run a temporary earth from the negative battery post to the rear loom earth point(s). Martin
    Last edited by ECS; 05-01-18 at 03:07 PM. Reason: spelling

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