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Thread: Instrument troubleshoot

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    Jedi Trainee Crankshaft's Avatar
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    Instrument troubleshoot

    My fuel and amp gauges stopped working at the same time. When something like that happens I first think of ground issues. Does that sound reasonable, and if so, where would be a logical place to begin to search?
    Phil

    1960 TR3A TS74517L
    1930 Ford Town Sedan

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    Great Pumpkin TR3driver's Avatar
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    Re: Instrument troubleshoot

    Doesn't make sense to me; the ammeter does not need a ground at all. Sounds like you have two unrelated problems (which can happen).

    Ground is definitely an issue with the fuel gauge, though. I always suggest adding a ground wire from under one of the mounting nuts, over to the ground tie point on the back of the panel. Or, if you don't have the panel out, you could run it to some other good ground. The factory relied on the ground through the mounting clamps, which is by no means reliable.
    Adding a ground wire to the fuel sender seems prudent to me as well. Mine runs down to one of the tank mounting bolts inside the trunk.
    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

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    Re: Instrument troubleshoot

    Thanks Randall, I'll definately try the sending unit. I had a ground wire in the mounting nut but might pull the dash to have a look back there as well.
    Phil

    1960 TR3A TS74517L
    1930 Ford Town Sedan

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    Yoda
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    Re: Instrument troubleshoot

    Randall has bailed me out all the time with electrical stuff, and I am far of being an expert, so I will try and make a wild theory here.

    When I think of the amp gauge, I think of how the gauge is in line of a hot wire and not across 2 wires like a volt meter. Which I guess a fuel gauge basically is--- a volt meter with hot and ground with resistance in the center. Having said all that, the 2 gauges are next to each other so maybe something happened, but yes not a direct correlation. If the glove box is out of your car or you do not have a heater, looking around the back of the dash is easier and that is where I would start. I would unhook one of the battery cables or loosen it, so I can unhook and re-hook, but start with it unhooked and look and see if something fell.

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    Re: Instrument troubleshoot

    Were I not such a goof and accustomed to making blunders like this I would not even tell what was found. Had wires switched on fuel gauge from when I cleaned it last year. Even had them labeled but still managed to cross them. Thanks again Randall and sp53 for the help and apologies for bothering you with such a trick. Still working on amp meter.
    Phil

    1960 TR3A TS74517L
    1930 Ford Town Sedan

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    Yoda
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    Re: Instrument troubleshoot

    Glad you found part of it. I would check for lose connections on the amp meter. It basically sits in the wirer of a hot lead and measures current as the current passes through it. I am not sure if an open or broke ammeter will shut the car down or not, but I think the charging system and the ignition light do not work if the ammeter is out because there was a post demonstrating that when a voltage regulator goes out that effects major parts of the whole system and the ammeter is right in line with the voltage regulator. So does your car start and the ignition light go out? Randall would know.

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    Re: Instrument troubleshoot

    A bad connection to the ammeter, or open circuit inside it will indeed shut down almost everything including the ignition and starter button on the dash. The horns would still work, and the starter from the rubber button on the starter solenoid; but not anything else.

    Only way to get the engine to run would be to "hot wire" the coil to the battery, and use the rubber button to crank it. But the ignition light might go out, if it gets power back from the hot wire to the coil.

    It's not impossible for the ammeter itself to fail, but I've never seen one that would not work and still pass current to the rest of the car. So more likely a wiring problem IMO, especially since you've been working on the wiring.

    One test would be to remove one of the wires at the ammeter (or at the other end) and see if anything still gets power from the battery.

    Power from the battery is tapped by the brown wire at the starter solenoid, brown wire runs from there over to the fuse block where it powers the horn fuse and then runs to the ammeter. The other side of the ammeter should be a brown/white wire, which runs back out to terminal "A" on the control box (regulator).
    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

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    Re: Instrument troubleshoot

    As I removed, tested wire continuity, cleaned and replaced connectors the problem has been fixed. As a bonus I became much more familiar with wiring diagrams. At my age, I don't buy green bananas anymore but it's never too late to learn and try new things. Thank you both for the input.
    Phil

    1960 TR3A TS74517L
    1930 Ford Town Sedan

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