Electrical Parasitic Draw? Not Sure

R82148V

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May 26, 2020
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Hello Everyone,

87 vert.

I know there are a ton of thread on this, but I'm having a heck of a time reading my DMM and understanding mA.
I believe to have a power draw somewhere. I have a new battery, fully charged, and within a week or so of not starting it, the batt will drain down to around 8 volts.
I charged the batt back up to 12.70 and within two days I'm down to 12.11.. I checked for a draw on the negative side of the batt and came up with this.
I know anything under 50 milliamps is ok, but I don't if this a draw over that or not?

To me it looks like 3 milliamps, but something is draining the batt quick. My question is is this really only 3 milliamps or is it well over 50?

Thank you for all your time!

-Rick
 

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Mustang5L5

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That is 3.4 milliamps, but for a parasitic draw, i'd expect to see something higher.

Most vehicles at rest pull around 20-50 milliamps. I forget what my fox pulls at rest as it's been a while.

A lot of DMM's only go to a max of 1AMP for current in DC. You'll have to see what yours is limited to. I use meters that have a max of 10AMP DC for troubleshooting parasitic draw. Most draws have been over an amp or so, and usually things like glovebox, vanity mirror or hood lights staying on
 
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R82148V

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May 26, 2020
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That is 3.4 milliamps, but for a parasitic draw, i'd expect to see something higher.

Most vehicles at rest pull around 20-50 milliamps. I forget what my fox pulls at rest as it's been a while.

A lot of DMM's only go to a max of 1AMP for current in DC. You'll have to see what yours is limited to. I use meters that have a max of 10AMP DC for troubleshooting parasitic draw. Most draws have been over an amp or so, and usually things like glovebox, vanity mirror or hood lights staying on
Thanks for confirming it was only 3.4 mA. I guess I was just over thinking it since I figured there was a draw because the batt keeps draining.
The DMM does have a 10 amp DC and when I check it, it reads 0.003. Actually it bounces from 0.001 to 0.003 and back.
I wonder why its only 3.4 mA when most cars pull 20-50. Is it safe to assume all is good with the system then?
 

limp

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New batteries can be bad too..... I had one that I could not figure out until a parts guy tested each cell with a gravity tester and found the bad cell.....
It happens
 

R82148V

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New batteries can be bad too..... I had one that I could not figure out until a parts guy tested each cell with a gravity tester and found the bad cell.....
It happens
I totally agree with you. The thing is, if the batt is disconnected, it'll hold the charge all day long, but once you hook it back up, the slow but steady drain begins.
Every hour or so you can see the volts come down.
 

limp

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I totally agree with you. The thing is, if the batt is disconnected, it'll hold the charge all day long, but once you hook it back up, the slow but steady drain begins.
Every hour or so you can see the volts come down.
Mine never lost the charge, it just had a hard time cranking the truck sometimes...... Amazing how bright the instrument lights became after a new " working correctly" battery ......
 

85GTStangGuy

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Could always start pulling fuses and monitoring the battery.

Or pull 'em all and put one in every hour. Should take less than ±15 hours.:O_o:
 

Mustang5L5

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Are you using the meter correctly? Need to pull a lead off the battery and connect the meter in series
 

R82148V

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Sure am. I've disconnected the negative cable and series in the meter between the cable and post.
Strange for sure!
 

R82148V

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Just pulled everything from the fuse block and also disconnected the starter cable from the solenoid. I didn't make a difference. It's still in this area.
I know you're saying this is only 3 milliamps which is nothing at all and well under the cap of 50, but something is draining that batt. I hope I am using the meter correctly and reading it correctly too. :doh:
 

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Mustang5L5

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I see what your problem is. Set it to A, not mA.

I just measured my car. the mA scale doesn't read, but with it on A, i get 0.03A at rest, which is 30 milliamps. I removed the hood light bulb for this reading. If i leave the hood light on (an LED), the draw is 0.08A which is 80 mA.

Make sure you also have the leads correctly positioned on the meter. Usually one to COMMON and the other to A.

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R82148V

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NICE!!!! I'll definitely put it on A and try it again.
I notice that you are testing in series on the positive side? I was doing the negative side.
I'll match you and see what I get.

Thank you!
 

Mustang5L5

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It doesn't matter which side. You should get the same values.

Some will say it's safer to test on the neg side due to less risk of shorting to something. I just did the test fast without paying attention
 

R82148V

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Ok I set it up the same way but used the negative side.
I suppose it's safe to say that there isn't any draw. I don't get it then why the batt drains away, but only when its hooked up. Batt has sat for two days unhooked and hasnt budget on voltage.

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Mustang5L5

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Try this. Do the same but open your drivers door. When you make the connection, your interior light should come on. You should see some draw.

If the light doesn’t come on, there is something going on with the connections or your meter
 

R82148V

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Ok, I tried it but with the driver door open. It then pulled .990
Closed the door and it went right back down to .001 - .003

I hope this isnt the case of a bad cell in the batt. I just picked this batt up.

What's the average time for a fox to kill a batt with no parasitic draw?

I always thought you were supposed to have some sort of pull like what you are pulling .024
Figured there was something wrong since im way low to .003

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limp

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OH NO, an Exide battery.... LOL.... That is what I had when we found the bad cell...... I will never use an exide again.....
I am not an electrical guru, but I wonder if when your battery is put under that tiny load, that is when it dies because it is faulty??? Just sayin.....
I had done a frame off restoration ( another project that got out of control) so that made it harder to diagnose as who knows what I did wrong with the wiring... Its been a long time ago ( #2 kid in the background would of been 38 this year) but the bad cell did not show up in a load test or a simple meter test for voltage if I recall which made it hard to find..
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Mustang5L5

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I’ve left my car sitting, at what I assume is 30 milliamps based on my reading today for a month or so and can still fire it up. In fact, I only use the trickle charger in the winter. In the summer I regularly go 2-4 weeks off the charger with no noticeable depletion.
 
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R82148V

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Excide.. I've heard good and bad things about them. The engine cranks without any hesitation so I figured the cranking amps are all there and not a bad cell. I kept the batt off since yesterday and the voltage didn't move. I hooked up the batt this morning and after 2 hours, it dropped from 12.38 - 12.30.. I THINK I might have found the issue. Well two issues that's causing the draw.
1) after reading a ton of posts about the Alternator usually being the culprit, I thought I would check it out. When the car runs, the Alt gives off over 14 volts so it is working. With the engine off, I pulled the top plug. The plug that goes where the brushes are. Once I pulled the plug, the reading dropped some.

2) after reading a ton of posts to check the wiring off the starter solenoid, I pulled one at a time starting with that small metal relay looking thing. That wire pulled didn't make the rest of the amps drop but the second one did! The BLUE wire when disconnected from the starter solenoid, the amps dropped straight to ZERO!

What is that black thing on the back of the alt called and would you know what the Blue wire is for on the SS?
 

R82148V

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UPDATE !


So after pulling the Alternator top plug, the plug that connects where the brushes are, some milliamps dropped. I left it disconnected over night expecting to see some sort of drop in voltage. I checked it this morning. Batt voltage didn't drop at all! Safe to say that the Alt and or the brush area is faulty even though the Alt does charge. I guess I'll take this time to upgrade to a 3G.

Thank you all for all the great advice, knowledge and especially the pics! most most most helpful!
 
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