Battery draw.

Discussion in 'Troubleshooting & Diagnosis' started by enjoy13760, Oct 8, 2019.

  1. enjoy13760

    enjoy13760 Veteran Member

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    Hey guys and gals I have a 72 z28 with no radio nothing that would cause battery draw on the inside of the car. Every few months or less my battery keeps dying with a new alternator Amps are great when running so alternator is fine..I’m getting a draw from some place, could it be my ignition in the car because sometimes I will drive the car turn it off and it’ll be fine for weeks and then other times I’ll drive the car turn it off and the battery would be dead within a day. Has anyone experienced this. I’m just at a point of putting on a cut off at the battery. thank you
     
  2. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

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    I guess there are more ways than one to skin a cat, but in this situation you'll need to put an amp meter on the battery and start pulling fuses one at a time. But before you pull any fuses, disconnect the alternator, see if that's your amp draw.
     
  3. Jim Streib

    Jim Streib https://www.flickr.com/photos/121766713@N04/albums

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    Yep, like Corky stated, you need a meter to get some measurements.

    It may be on a fused circuit on one or more of the fuses in the fuse block or could be an issue with the alternator.

    Your car had originally an external voltage regulator and if still in place could have issues.

    I've also seen issues with underhood lights being on at the wrong time and adjusted wrong.

    Try and keep the battery from getting fully discharge as this is not good for them.

    While you could put on a master on/off switch, I would try and find the true issue of the battery drain.

    Intermittent problems are also harder to find and track down so keep at it.

    Jim
     
  4. flht99b

    flht99b Veteran Member

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    One thing to check is the battery ground. My wife's new in 2006 DTS Performance Sedan did the exact thing. Under warranty dealer changed batteries, multiple trips to service department and even a GM engineer had the car for several days. Their "fix" was to put the car on a maintenance charger that they supplied and wired up. Pissed me off. So in a couple of hours I determined there were times the negative battery cable which was bolted to the unibody under the rear seat (where the battery resides) showed high resistance. Unibody was dipped in the black plated primer, I chased the female threads in the unibody for the negative cable ground and problem was resolved. I put the fix on the Caddy forum and GM picked it up as a TSB as many others were experiencing the same problem.
     
  5. enjoy13760

    enjoy13760 Veteran Member

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    On a normal working system will the battery show any type of draw. Just so I know when doing the checks I know what amount of draw would be convicted normal. Also how do I check resistance and the negative.
     
  6. enjoy13760

    enjoy13760 Veteran Member

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    Considered normal
     
  7. flht99b

    flht99b Veteran Member

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    Ohm meter between the end of the negative cable to where it is bolted to the car or engine. Look for corrosion or plating where the cable bolts to. Check the both ends of the negative cable and run the ohm meter between both ends of the cable.
     
  8. tom3

    tom3 Veteran Member

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    A 72 should have no draw - except the clock. Try a small 12 volt light bulb, unhook a battery cable, run the current through the small lamp, should not light at all. A multimeter that measures DC milliamps would maybe be better if you have one. If showing a current flow start pulling fuses. But as Corky says a diode in the alternator could be leaking current back through and draining the batt.
     
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  9. Jim Streib

    Jim Streib https://www.flickr.com/photos/121766713@N04/albums

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    On an original older car like yours an ammeter placed between the negative battery post and the negative battery cable end should show 0.00A which is no draw. Clocks can draw power but I think on the older ones, how the originals worked was they only drew power when a solenoid in the clock mechanism was activated to wind up a clock spring and then didn't draw power until the spring would down.
    If you were to measure something like 0.01 to 0.02, then this to me would mean either you have digital radio in the car or a quartz conversion clock. This small draw would not drain a good battery down over the course of a month to not allow it to start and crank the motor over. This is just a minor draw.
    If you were to measure let's say 0.10A or so, then this makes me think possibly a relay coil is energized. Relays were used on some cars for emissions but I think on yours even if you do have a TCS system then this was only wired to a keyed 12V source and not constantly on to where if it was wired to a constant voltage then it could drain the battery down.
    On your car you should have a large cable between the battery negative post and the engine and then a smaller gauge fusible link wire from the battery negative post to either the fender or radiator support. On these spots, take them apart, clean the surfaces on both the surface where they connect to as well as the top and bottom surface of the connector and bolt things back together.

    Also too, look real close at things under the hood, under the dash, in the trunk, and so on. Who knows, you might have something on the car that you do not know about and was added at some point in the car's life. I've seen alarms and tracking systems very cleanly installed to where it's hard to tell it was even added.

    Jim
     
  10. xten

    xten Veteran Member

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    I had a pin switch in the door jamb go bad. When I got out of the car and shut the door, the interior lights would go out, but sometimes the tube on the switch would slide into the mounting nut and the interior lights would come on. Mine was intermittent, so it was hard to find. I found it by accident. Went into the garage while dark and saw the interior lights on. Drove me crazy. If you opened the door the tube would pop back out of the nut and work as it should.
     

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