check for parasitic battery drain

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  #1  
Old 05-12-13, 12:23 PM
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check for parasitic battery drain

I want to check for parasitic battery drain on my '93 Grand Wagoneer. I've done some background reading on the methods of testing and am still unclear on my understanding of the testing method, as some seem to say check between the negative post and the negative cable, and some seem to say check between the postive post and the positive cable, and descriptions of where to set the meter dial seem to vary depending on the style/type of setting options on different style/types of meters. First of all, my multimeter dial is as shown here, with the dial now in the DC volts scale range at 20.
So far, what I've tried is removing the negative battery cable from the battery post and then touching one probe to the negative post and the other probe to the disconnected battery cable. At the setting shown in the picture (20 on the DC scale of the dial), I'm getting a readout of 12.62.
I've made sure everything is turned off, doors are all closed, key out of the ignition, etc. before doing the test as I described above.
1. Do I have my meter set properly for the test as shown/described?
2. Should I be testing between the negative post and negative cable with my probes, or should I be testing instead between the positive post and the positive cable?

Any comments/help/advice appreciated.
 
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  #2  
Old 05-12-13, 12:40 PM
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You need a meter with AMP's reading capability. That meter does not have that provision so it won't help you in this job.


Just to elaborate on parasitic draw diagnosing methods. It doesn't matter if the current reading meter is in the positive or negative side. The only difference is the polarity of the meter leads. Most current reading meters have a 2A or 10A protection fuse based on 2 or 10 amp max. You need to be very careful when checking current draw in a vehicle. It's very easy to excede that current and either pop the fuse or the meter.
 
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Old 05-12-13, 12:43 PM
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You want to be testing for ohms, not volts. Do the same thing, just set your meter in a high ohm range, then click it up one notch to get a better more accurate reading. Be sure you pull the light bulb out of the socket under the hood, as it is obviously a parasitic drain. As far as post, it won't matter much, but I usually do the positive versus the positive cable.
 
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Old 05-12-13, 12:57 PM
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You need a meter with AMP's reading capability. That meter does not have that provision so it won't help you in this job.
You want to be testing for ohms, not volts. Do the same thing, just set your meter in a high ohm range, then click it up one notch to get a better more accurate reading.
Okay, will my meter not help me in this job as PJmax mentioned, or can I set the meter on one of the high ohm ranges and then test as chandler suggested?
 
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Old 05-12-13, 01:15 PM
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If you were looking for a short in the wiring you would be using an ohmmeter.

In your case you want to measure the current draw off your battery.
 
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Old 05-12-13, 01:20 PM
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Well dangit anyway. Guess I can't measure current draw off the battery with this meter then. Have to somehow acquire a meter that will. Thanks. At least now I know this much.
 
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Old 05-12-13, 01:30 PM
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An easy way to check for parasitic draw is put a 12 volt test light in the circuit. It can be in series in the positive or negative line. The light should be very dim or almost out. Open the car door..... it will get bright. Close the door and it will get dim. Remember in most cars there are control modules that draw continuous power from the battery. Upon battery reconnect.....their current draw is high. After a minute or so the modules should go to sleep and draw nearly no current.

A cool thing about the test light method is that it's easy to see when pulling fuses out one at a time looking for the problem circuit. Normally the fuse box is under the dash so to be able to look out and watch the light is a real plus.
 
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Old 05-12-13, 01:48 PM
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With the method Squll is using if there is a draw it will show voltage. No draw no voltage.
 
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Old 05-12-13, 01:52 PM
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With the method Squll is using if there is a draw it will show voltage. No draw no voltage.
Yes I realize now the method I was trying to use initially was incorrect.
 
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Old 05-12-13, 01:57 PM
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An easy way to check for parasitic draw is put a 12 volt test light in the circuit.
All I have in regard to a test light is this thing and I think it's just to measure continuity anyway. Actually I don't even think it works; I think the light bulb is bad. I suppose I might be able to at least check it with my other meter.
 
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Old 05-12-13, 02:54 PM
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That is a neon voltage tester, probably for line voltage. I mis spoke as well on my OP with you. You don't need to be checking Ohms, but Amps as PJ said. A meter with Amps settings as well as Amp plugins will be necessary. I was thinking of trying it with the battery out of the mix, but it would be better to have it in the mix and check for amps bleeding.
 
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Old 05-12-13, 04:05 PM
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An easy way to check for parasitic draw is put a 12 volt test light in the circuit.
I dug around and came up with this test light

It can be in series in the positive or negative line.
Not sure what is meant by that. Just put one end of the test light on a disconnected battery cable, and the other end on the post where the cable would otherwise be connected?

Anyway, I'm fairly certain this isn't the type of test light needed. I guess this is a "circuit tester"?
 
  #13  
Old 05-12-13, 04:29 PM
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You really need to know the current drain to determine how long your car can not run but still will start. A reading of 25 ma. or below would be typical and could let a car sit for a month and it will still start.
 
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Old 05-12-13, 04:38 PM
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Okay, thanks DMCman; that's good to know.
Then apparently the fact remains I will need to get a meter with AMP's reading capability to check properly for parasitic drain. Unfortunately I doubt anybody I know has one I can borrow, and I can't afford to just run out and buy one.
 
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Old 05-12-13, 06:10 PM
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Yes....that light will work fine. Until you locate an ammeter you could experiment with the light.
It goes inline between battery post and cable....... either positive or negative side.

Try it....you can't hurt anything.
 
  #16  
Old 05-12-13, 06:36 PM
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sgull,

You’re checking for “Amps” not volts. Visit the links below.

How To Perform a Parasitic Draw Test - EricTheCarGuy - YouTube

How to Find a Parasitic Battery Drain: 9 Steps - wikiHow

Thank You
AMY
 
  #17  
Old 05-12-13, 08:15 PM
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sgull,
You’re checking for “Amps” not volts. Visit the links below.
How To Perform a Parasitic Draw Test - EricTheCarGuy - YouTube
How to Find a Parasitic Battery Drain: 9 Steps - wikiHow
Thank You
AMY
Right. I do understand I need to check for amps not volts, and as well that I'm going to need an ammeter to perform the tests as described in the links you provided. In fact I had already visited those links before posting here, but was unclear of the meter settings as described in those links as compared with meter settings available on my particular multimeter as pictured in my first post here. Thanks
 
  #18  
Old 05-12-13, 08:22 PM
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Yes....that light will work fine. Until you locate an ammeter you could experiment with the light.
It goes inline between battery post and cable....... either positive or negative side. Try it....you can't hurt anything.
Okay sure PJMax, I'll go ahead and experiment with that light then, for now anyway. I'll keep in mind what you mentioned about it in post #7, and see what I might be able to decipher if anything. Thanks
 
  #19  
Old 05-13-13, 02:14 AM
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Sgull,

I have a busy day ahead of me today, so I wanted to get this out to you early, because I won’t have time later.

Switch your Digital Multi meter to DC AMPs. Amps is usually indicated by an "A" on the Multi meter Switch. AC is usually shown as a "~" symbol and DC shown as a "-" symbol. You usually have to move the multi meter positive lead to a separate socket on the multi meter to check for amps. Sometimes there are 2 sockets, (a high range and a low range). Always test on the highest setting first. For example: High setting on your multi meter may be 10 Amp. Test on the 10 Amp setting first, then if the current drawn is less than your Multi meter’s (low setting) move to that setting and keep testing. For example: On my multi meter the low setting is 0.3 Amps. Also indicated as 300mA (mA x 1000 = A).

Remove the battery’s positive cable.

Connect the multi meter's positive probe to the battery's positive post while simultaneously holding the negative probe from the multi meter up in the air, to keep it away from anything metallic.

Place the negative probe of the multi meter on the end of the removed positive cable to complete the circuit.

That’s right, you're putting a negative on a positive, but its ok, because if the drain is severe enough, you're most likely to blow a fuse or two, which will identify the problem area.

Above I said to remove the positive battery cable because that is the way I do it. You can do the same test with the negative battery cable removed. In fact for you that may be a better way to do the test, because there would be no way for any electrical issues to occur by accidently grounding the negative probe from the multi meter. i hope you understand what I'm saying here.

Thank You
AMY
 

Last edited by AMY FIX 62; 05-13-13 at 02:43 AM.
  #20  
Old 05-13-13, 08:27 AM
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I was able to come up with a meter that has amp measuring capability. It only has one setting for checking amperage, which is 200mA. I'm not really clear on whether that's adequate to perform the parasitic draw testing as has been discussed here. In this picture you can see the (rather blurry) dial on the meter set at the 200mA setting, and the readout with the meter connected between the negative post and the negative cable.
It would be great if this indicates there is apparently no excessive parasitic draw occuring and I don't need to worry about it now. Comments?
 

Last edited by sgull; 05-13-13 at 10:29 AM.
  #21  
Old 05-13-13, 12:48 PM
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squll,

EVERYTHING you need to know has been posted already. Thing is I’m really busy right now. With that being said (and at this point), what exactly is the problem, and why are you looking for a “Parasitic Battery Drain” in the first place?

Thank You
Amy
 
  #22  
Old 05-13-13, 02:06 PM
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EVERYTHING you need to know has been posted already
Maybe so, but I'd still like to get a comment(s) to help me know if with the meter as shown set and connected in my last post here whether the readout indicates there is apparently no excessive parasitic draw occuring. I'm assuming this shows there is in fact no excessive parasitic draw occuring, but I'm not as experienced/knowledgeable as others here about the testing to rely on whether my test was adequate.

what exactly is the problem, and why are you looking for a “Parasitic Battery Drain” in the first place?
The problem was that after the vehicle, with the battery fully charged, would sit for a week or several days or whatever without being started, the battery would fail to be strong enough to start the vehicle. The previous owner said he had information or a hunch or something that it was a malfunction somewhere in the factory security system (anti-theft) draining the battery. I've disabled the security system completely now and am just trying to determine whether that helped or not, and just checking in general otherwise, for the sake of checking, for any excessive parasitic battery drain.

Thing is I’m really busy right now.
I wouldnt expect replies from anyone if replying is somehow inconvenient. I'm busy too but I think that's irrelevant.
 
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