1968 Barracuda 383/4spd

Electrical and Ignition

  1. vesparex

    vesparex New Member

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    I have an oil pressure indication issue.
    Mechanical test confirms oil pressure. Done.
    Ground grey wire unhooked from sender and turn key on, gauge sweeps smoothly to high then fluctuates, I assume the fluctuation means that the voltage reg is working.
    Multimeter at terminal end, key on, unhooked from sender, moves to 4-5v, again, fluctuating.
    Sender (for dash gauge, not idiot light) grounds fine to the engine and body with a continuity test.
    Sender (new) ohms test shows 19-22 at idle.
    But put it all together and dash gauge doesn't move. All other gauges operate, temp, fuel and amp. All operating.
    What am I missing?
     
    Last edited: Nov 20, 2020
  2. jaws

    jaws I put the fun in dysfunctional FABO Gold Member

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    Line 3 if you unhook the wire and the gauge moves, you have a volt bleed somewhere. Do you have a 68 service manual?
     
  3. vesparex

    vesparex New Member

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    [QUOTE="jaws, post: 1973220409, member: 3343"[ Do you have a 68 service manual?[/QUOTE]

    No, I do not.

    Duane
     
  4. Demonracer

    Demonracer 71 Demon 00 Ram 16 Chrysler 300S 05 Caravan FABO Gold Member

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    Get you a FSM, they can be downloaded for free on several sites.
     
  5. AJ/FormS

    AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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    The temp gauge and the fuel gauge are both powered up by the same dash-gauge regulator. That regulator is just an on/ off switch with a heater in it. When powered up, all it does is continuously turn on and off, in a duty cycle that accomplishes an average of about 5 volts. The factory gauges are so slow that they rarely catch the fluctuating.
    Of course the oil-pressure sender has to vary it's ground resistance with changes in oil pressure, to make the gauge work...
     
  6. vesparex

    vesparex New Member

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    I found a 1967 FSM for A Bodies this weekend and read through the cluster/gauge portion, repair and trouble shoot portion. Did not see anything about how to check for voltage bleed.
    Can someone give me a little insight?

    D
     
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    • AJ/FormS

      AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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      Put an analog ohmmeter across your oil pressure sender to ground. Take a reading with engine off, then watch the needle and start up the engine; the needle must swing . And must not go to open-circuit, nor to full continuity. The actual numbers are less important than, than the actual swing.
       
    • RedFish

      RedFish Well-Known Member

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      sender with oil pressure shows 19 to 22 ohms. that should move the needle to about middle of range/gauge screen. Shorting the wire to the block is zero ohms test. That can make a faulty gauge do what normal the 80-10 ohm signal would not. Zero ohms should take the needle to its max position and hold it there. A fluctuation is not normal. The beam should not heat and cool fast enough to fluctuate the needle if the limiter is working properly.
      What I would do... short the temp sender wire to the block. If this needle fluctuates also, the limiter output is the problem.
      Your fuel gauge has a slither of metal on its backside that sits on a unpainted spot in the housing. This provide ground path for the limiter. A few owners have found a poor contact here to be the problem.
       
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