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  1. #1
    FEP Power Member fgross2006's Avatar
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    Default Volt Gauge set up

    I had my stock AMP gauge refit to be a stock looking Volt gauge last autumn. I was told to just ground it and tap into a 12 volt key on source in the dash to set it up. I did it like that and it does light up the volt gauge but I have noticed that all it seems to be doing is reading dashboard voltage rather than give me an accurate reading on how many volts my alternator is charging my battery with.

    For example, then I hit the directional the volt gauge jumps to the left with each click of the blinker. If I have music on loud, the thundering bass makes the volt needle flicker to the left. Hit the headlights, drop of the needle. Hit the hi beams, lower drop of the needle.

    By comparison my F150 was stock set up with a volt gauge and it does not behave this way when using any power in the dash. The only difference I can see is the F150 was factory wired to read the charging system, not the dashboard voltage usage.

    Is there a better way to maybe run the volt gauge power wire to the alternator stator to just isolate the charging status?

  2. #2
    FEP Super Member cb84capri's Avatar
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    Your problem is more than likely the grounding circuit if you are tied into G201 with all the other gauges in the cluster. I would try to supply the gauge with its own ground wire temporarily to see if it remedies the jumping with the turn signal - unless you already have a dedicated ground for that going somewhere else. A wire with alligator clips on each side works well for this as long as you don't touch power.

    What circuit are you tied into for ignition switched power?

    Cale

  3. #3
    FEP Power Member fgross2006's Avatar
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    Quote Originally Posted by cb84capri View Post
    Your problem is more than likely the grounding circuit if you are tied into G201 with all the other gauges in the cluster. I would try to supply the gauge with its own ground wire temporarily to see if it remedies the jumping with the turn signal - unless you already have a dedicated ground for that going somewhere else. A wire with alligator clips on each side works well for this as long as you don't touch power.

    What circuit are you tied into for ignition switched power?

    Cale
    I grounded to the negative post on the tach in the cluster and the positive is tapped into a 12 key on wire I found under the dash.

    I am 98% finished with my interior restoration so I prefer not to pull the cluster again. I was hoping I could route the positive lead to engine compartment and possibly go to the battery. I read this can be done with a relay to insure there no power drain with key off. I would need to find the right kind of replay to use in that setup.

    What I want to see is a true visual of what voltage my battery is charging at. Also if possible, with key on acc I'd like to see the battery voltage when the car is off.

  4. #4

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    I would start by using a handheld meter to take an independent measurement of the circuit you tied into to
    drive the voltage gauge, against a good bare-metal ground, to make sure whether or not your voltage gauge
    is simply telling you what it sees. There is a LOT of stuff being powered through a single fusible link, and you
    will also get more voltage fluctuation on some 'ignition-on' fuse circuits than others. You need to quantify what
    is really going on, with real numbers.

    I would also use that same handheld meter to verify that you never see more than about 0.1V between the tach
    ground stud and that same bare-metal ground, under the same test conditions.
    Cheers,
    Jeff Cook

    '85 GT Hatch, 5-speed T-Top, Eibachs, Konis, & ARE 5-Spokes ... '85 GT Vert, CFI/AOD, all factory...
    '79 Fairmont StaWag, 5.0, 62K original miles ... '04 Azure Blue 40th Anny Mach 1, 37K original miles...
    2012 F150 S-Crew 4x4 5.0 "Blue Coyote"... 65 coupe, 289 auto, Pony interior ... '67 coupe 6-cyl 4-speed ...
    '68 Vert, Mexican block 307 4-speed... '71 Datsun 510 ...
    And a 1-of-328 Deep Blue Pearl 2003 Marauder 4.6 DOHC, J-Mod, 4.10s and Lidio tune

  5. #5
    FEP Power Member fgross2006's Avatar
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    Default

    Quote Originally Posted by JACook View Post
    I would start by using a handheld meter to take an independent measurement of the circuit you tied into to
    drive the voltage gauge, against a good bare-metal ground, to make sure whether or not your voltage gauge
    is simply telling you what it sees. There is a LOT of stuff being powered through a single fusible link, and you
    will also get more voltage fluctuation on some 'ignition-on' fuse circuits than others. You need to quantify what
    is really going on, with real numbers.

    I would also use that same handheld meter to verify that you never see more than about 0.1V between the tach
    ground stud and that same bare-metal ground, under the same test conditions.
    Understood, but is it feasible to run the Volt gauge positive to the battery to get a real voltage charging result? How is a volt gauge set up electrically in a car that comes with it stock from the factory?

  6. #6

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    It's definitely feasible, but if your electrical system is really doing what your gauge says it is, I would be looking
    to understand that better. This is why I suggest diagnosing the problem, rather than just making changes.

    Your existing electrical system already has a pair of wires that could be used to provide a more accurate reading
    of battery voltage. They're the ones that used to go to your ammeter. But Ford did not have to resort to such
    measures on the aero-nose Mustangs (or on your F150), so again, I would want to put some real numbers to
    those gauge fluctuations.
    Cheers,
    Jeff Cook

    '85 GT Hatch, 5-speed T-Top, Eibachs, Konis, & ARE 5-Spokes ... '85 GT Vert, CFI/AOD, all factory...
    '79 Fairmont StaWag, 5.0, 62K original miles ... '04 Azure Blue 40th Anny Mach 1, 37K original miles...
    2012 F150 S-Crew 4x4 5.0 "Blue Coyote"... 65 coupe, 289 auto, Pony interior ... '67 coupe 6-cyl 4-speed ...
    '68 Vert, Mexican block 307 4-speed... '71 Datsun 510 ...
    And a 1-of-328 Deep Blue Pearl 2003 Marauder 4.6 DOHC, J-Mod, 4.10s and Lidio tune

  7. #7
    FEP Power Member fgross2006's Avatar
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    Default

    Quote Originally Posted by JACook View Post
    It's definitely feasible, but if your electrical system is really doing what your gauge says it is, I would be looking
    to understand that better. This is why I suggest diagnosing the problem, rather than just making changes.

    Your existing electrical system already has a pair of wires that could be used to provide a more accurate reading
    of battery voltage. They're the ones that used to go to your ammeter. But Ford did not have to resort to such
    measures on the aero-nose Mustangs (or on your F150), so again, I would want to put some real numbers to
    those gauge fluctuations.
    The reason I didn't use either of the 2 AMMETER wires for the Volt gauge was because they are hot with key off so I didn't want a voltage drain.

  8. #8

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    Quote Originally Posted by fgross2006 View Post
    The reason I didn't use either of the 2 AMMETER wires for the Volt gauge was because they are hot with key off so I didn't want a voltage drain.
    Understand, but you mentioned running a wire and using a relay, so I was merely pointing out that you already
    have those wires in place, should you decide to go that route. Not saying you should, mind you...
    Cheers,
    Jeff Cook

    '85 GT Hatch, 5-speed T-Top, Eibachs, Konis, & ARE 5-Spokes ... '85 GT Vert, CFI/AOD, all factory...
    '79 Fairmont StaWag, 5.0, 62K original miles ... '04 Azure Blue 40th Anny Mach 1, 37K original miles...
    2012 F150 S-Crew 4x4 5.0 "Blue Coyote"... 65 coupe, 289 auto, Pony interior ... '67 coupe 6-cyl 4-speed ...
    '68 Vert, Mexican block 307 4-speed... '71 Datsun 510 ...
    And a 1-of-328 Deep Blue Pearl 2003 Marauder 4.6 DOHC, J-Mod, 4.10s and Lidio tune

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