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Chasing ground

Discussion in 'General CB Services Discussion' started by Ziploc, Feb 3, 2021.

  1. Ziploc

    Ziploc Well-Known Member

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    Guys, how can I check with a multi meter if my ground from amp to seat bolt is actually grounded good . Thanks


     

  2. Robb

    Robb Yup

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    Use the resistance function and see the amount of resistance between the amp chassis and the seat belt bolt.
    Best to use braided copper wire; not regular wire.
    Should read very l o w resistance.
     
    #2 Robb, Feb 3, 2021
    Last edited: Feb 4, 2021
    Handy Andy and Ziploc like this.
  3. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    With the meter set on ohms, put one probe on the amp cable and the other probe on the battery negative. Might need an extension wire. This reading should be very close to the reading you get by touching the probes together by themselves. This will tell you if there is a connection, but will not tell you how much power it will handle as the meter provides very little current.
     
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  4. Ziploc

    Ziploc Well-Known Member

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    Neg amp cable? Like the barrel screw
     
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  5. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    Yes that should work.
     
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  6. Ziploc

    Ziploc Well-Known Member

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    So I had the ohm setting on. Seat bolt to barrel connect to amp it was like 0.02
     
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  7. Dmans

    Dmans Sr. Member

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    I would use my multi meter and measure voltage on both positive and negative terminals of the battery. Then keeping your positive terminal on the battery post, move your negative lead to the "seat bolt" negative and see how much difference there is.

    A good ground should provide little to no difference from what is measured at the battery.

    73
    David
     
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  8. Ziploc

    Ziploc Well-Known Member

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    It’s 14.2 at battery. So keep one on positive on battery and the other probe to seat bolt?
     
  9. Dmans

    Dmans Sr. Member

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    Yes. Voltage should be the same as measured at battery.

    Might not hurt to load the battery and check again. I.e. turn on all lights (high beams) and any electrical device you can and measure both again. Loading the battery with a battery load tester would be better. If at 50-75 amps load on battery your "seat bolt" negative doesn't read the same as battery voltage, it is not a good ground.

    73
    David
     
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  10. Ziploc

    Ziploc Well-Known Member

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    Dam wire ain’t long enough
     
  11. Dmans

    Dmans Sr. Member

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    You could also check from your amplifier DC positive to your "seat bolt" but you will be checking both sides of your DC supply to your amp. If it doesn't measure close to or exactly what the battery shows, your issue may be in the positive supply or negative return lead.

    Probably best to check both (positive and negative) back to the battery separately to determine where the power loss is. But if the "Dam wire ain't long enough" you got to compromise.

    73
    David
     
  12. Ziploc

    Ziploc Well-Known Member

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    Battery tests 14.1 truck running then ran negative to seat bolt it was 13.9 to 14.0
     
  13. Ziploc

    Ziploc Well-Known Member

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    What’s happening it I key up my volts drop but recover quickly then I modulate and drops but recovers again
     
  14. Dmans

    Dmans Sr. Member

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    How far does it drop? If you stayed keyed up, how far will it pull the voltage down?
    Example-30 second key and battery is at 13.5 volts? 11 v? etc

    How fast does it recover?
    Example-After 30 second key, recovers in 30 seconds? 10 seconds? With engine at idle(1000 rpm) or at 2000 rpm fast idle?

    I'm assuming you have large enough cables to your amplifier to carry the current?
    What is the condition of the amplifier?
    What is the maximum amp draw of the amplifier?

    So far it sounds normal to me. If improvements could be made, a larger battery (more storage capacity) could lessen the voltage sag or a larger alternator (higher current output) to recover the sag more quickly could be added.

    73
    David
     
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  15. Ziploc

    Ziploc Well-Known Member

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    My Lincoln 2 plus shows 14.1 key up amp on drops to 13.0 them I modulate it’s recovers back to like 13.5 13.8
     

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