Off Key Battery Draw Test Help Needed

Discussion in 'Electrical Systems' started by SG71SS, Feb 15, 2019.

  1. SG71SS

    SG71SS Veteran Member

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    Often my bone stock 79 T/A sits 2-3 weeks between drives and the battery will be slow cranking and many times won't have enough juice to start the car. My 71 Camaro SS sits the same amount of time and always has strong crank and the battery seems always charged.

    Using my Actron multi meter I first tested the battery and it came back at 12.44 volts so right now it's a little low at around 75% charged.

    Next I tried to do an "off key battery draw" test by disconnecting the negative cable, putting the tester selection knob on Amps, moving the red lead to Amps and from what I understand I should see some current on the multi tester when touching one probe to the negative cable and the other probe to the negative battery post. But I see nothing. It reads 0.00. I used alligator clips to hold them in place. I also put a regular 12V test light between the cable and the post and the test light did not light up. I figured I should have some draw from the clock at least right?

    As soon as I reconnect the battery and peek into the car through the driver's side window I can see the clock turning. During the off-key test, shouldn't I also see the clock turning since current should be running through the probe?

    Any tips are appreciated!
     
  2. lightly-modded

    lightly-modded Member

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    From what I can tell you're doing everything correctly. And you are correct the clock will run during the test. If it is not then it is your meter. Either you dont have it set up correctly (sounds like you do but I don't have your meter) or the fuse in your meter (usually a 20 amp slow blow) is blown.
     
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  3. SG71SS

    SG71SS Veteran Member

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    Thank you lightly-modded!

    I opened up my tester only to find the fuse fried like crispy chicken! Omg... :screwup: Have no idea how this happened. Think I'll just buy a whole new analyzer.
     

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  4. ULTM8Z

    ULTM8Z Veteran Member

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    try putting an small incandescent bulb in place of the multi meter and see if you get any illumination. if it does then the meter is not reading...

    these multi meters typically have self protection fuses in them. it could be blown.

    you could also try this with the multi meter... open the trunk and when the light illuminates, see if the multi meter reads anything. you should get something on the meter at that point...

    these tests would at least tell you if the meter is malfunctioning.
     
  5. budro6968

    budro6968 Veteran Member

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    Good call. Interesting thought his test light did not light. Was it B/C the bulb needed a full 12V to light. I would think that it would be at least a dim light. Could it be the Diodes in the Alternator that bleeds off? Have to eliminate that as a cause. This stuff is always fun to chase. Maybe even a door jam switch?
     
  6. lightly-modded

    lightly-modded Member

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    The more of a load on the battery, the brighter the light will be. There might not have been enough to light up the tester, or it might have been so dim that he didn't notice it. An led test light would have a better response. Another thought would be swapping the batteries in the two camaros. As a battery ages it weakens and becomes easier to draw down. I would also check grounds. While losing a little over 25% of its charge over 2-3 weeks (assuming it was fully charged to begin with) does mean you have a small draw, it should still turn the engine over with relative ease (also assuming the battery is properly sized). A bad ground could reduce the charge going into the battery while also increasing the starter load and causing it to turn slower.
     
    Last edited: Feb 15, 2019
  7. lightly-modded

    lightly-modded Member

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    Just looked at the picture, looks like more than just the fuse got cooked. Did you have the test leads in the Amps location when you went to check battery voltage? Even with the meter off that could send full battery amps through the meter, cooking it.
     
  8. hogg

    hogg Veteran Member

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    Most of the camaro clocks are electric,windup type,they windup and then run for a minnet,,, or two with out power untell it run down, Aset of points touch,powering a .MAgnet that pulls the ponts apart again,,,rewinding tbe clock

    p a
     
  9. Twisted_Metal

    Twisted_Metal Administrator Staff Member Lifetime Gold Member

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    ^+1 Exactly correct.
    The factory clock only draws power for a second every couple of minutes.
     
  10. tom3

    tom3 Veteran Member

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    Newer radio installed in the 79? Those draw some current fulltime as do electric remote locks. I usually use a 194 light bulb to check for draw or power up an ECM when the battery has been disconnected for a good while.
     

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