Parasitic battery draw with new harness

[BigNasty]

Hi everyone,
New to the forum. Searched everywhere to find a solution in the forum but this seems a bit unique. If you know another answer elsewhere, please point me to that discussion.
Have an 1982 J10 with AMC 360 and 727 trans. The wiring was in serious trouble when I bought it 2 years ago. Replaced the harness with a Rebel wiring harness, 15+3 circuit system. Great system, great quality wiring, and instructions were decent but not as thorough as something like Painless...though the price for Rebel was painless. Anyways, took roughly 5 weeks to remove the harness and replace with new. Followed the instructions along with a proper J10 wiring diagram for things like wiper switches and ignition circuit. Everything works great and no issues except my brand new battery goes dead after about a week...but not always.
What I mean is, I can drive it, park it and a week later it goes dead. Charge it up overnight, drive it, park it for 3 weeks and it doesn't go dead. Voltage is low but not so dead that it won't start. Even replaced the OEM size battery with an 800 CCA battery for other reasons but this draw was one of them.
I have done a parasitic draw test several times and it reads .005 amps. Tested my Chrysler 300 and my Ram 1500 and both are roughly .030 amps which is considerably more but they don't go dead weeks later. My understanding, most cars can have a draw of 50mA and not kill a good battery for months.
So my question is, what can cause draw intermittently? Can an alternator or starter backfeed intermittently? Can a brand new Duraspark module backfeed...intermittently? Is there some sort of order of operation I am not performing before I do the parasitic draw?
Really stumped on this one. Any help, suggestions, or places to reference would be greatly appreciated.

[BigNasty]

Forgot to mention that the dash is not stock. Full 6 gauge Jegs gauge package with hall-effect speed sensor. Yes, I tested the speed sensor by unplugging it. No difference in amp draw and doesn't seem to effect the speed of the battery going dead....when it does go dead.

[will e]

Welcome to the board.

My old mustang had a glove box light that would sometimes stay on and cause a similar problem.
Park the truck in a garage, close the garage door and turn out the garage lights. Once your eyes adjust see if you can see any light.
What type of ignition are you using?

[tgreese]

Welcome from Boston.

Suspect if the problem is intermittant, you have not seen it yet. Do you have a modern battery tester? It will show you the battery condition in terms of amp-hours. This will tell you how large the drain was (starting minus ending divided by time) and give you a chance of catching the condition while it's happening.

Or, you could disconnect the battery and test over a couple of weeks. This may give you confidence that the battery is not defective.

Yes, an SI alternator can be a drain (the regulator in the alternator). BTDT. Hard to draw a conclusion with an intermittent problem and only a negative test (ie no result implies problem is gone); however, you could unplug the alternator and see if the problem goes away. You may need to disconnect the charge wire too.

[BigNasty]

Thanks Will, it is spartan as far as lights inside the cab, which is to say it doesn't have any. This is a bug out vehicle and only has enough "functions" to allow it to run and drive on the road. No frills. But with that said, it has been in my shop for over a month and have never seen any lights from anywhere. Not saying it ever does, just not when I come in when the lights or off.
The ignition is the stock using coil and Duraspark box, i.e. no points or HEI.

Welcome to the board.

My old mustang had a glove box light that would sometimes stay on and cause a similar problem.
Park the truck in a garage, close the garage door and turn out the garage lights. Once your eyes adjust see if you can see any light.
What type of ignition are you using?

[BigNasty]

Thanks Tim. Yes, I do have a modern battery tester and have been taking daily pictures of the results for the past few days. The battery is good but showing a drain of 4-6% each day (taken roughly the same time of the day). Slow, steady drain but no draw of a size that makes the dead battery result. Makes ZERO sense. So frustrating but not giving up hope which is why I am reaching out to a group of like minded folks.
I tried to attach photos but they are all too large to post here. Will try later to reduce them on my phone and attach again.
Also, do you think it is possible that certain spots of the alternator could provide a "direct" draw spot where shutting off the engine places the draw one day but the next time it is sitting in a "no contact" spot where there is no draw? I guess I can test that with the draw test leads hooked up, removing the belts, and turning the alternator pulley slowly and watching the multimeter. Surely worth a try, right?

Welcome from Boston.

Suspect if the problem is intermittant, you have not seen it yet. Do you have a modern battery tester? It will show you the battery condition in terms of amp-hours. This will tell you how large the drain was (starting minus ending divided by time) and give you a chance of catching the condition while it's happening.

Or, you could disconnect the battery and test over a couple of weeks. This may give you confidence that the battery is not defective.

Yes, an SI alternator can be a drain (the regulator in the alternator). BTDT. Hard to draw a conclusion with an intermittent problem and only a negative test (ie no result implies problem is gone); however, you could unplug the alternator and see if the problem goes away. You may need to disconnect the charge wire too.

[BigNasty]

Reduced the pics and attached from prior reply to Tim earlier. Not sure how the order will show but goes from 100 to 87% in 3 days. Yet, .005amps in my draw test. ????
Brand new DieHard 800CCA dual post battery purchased last month and charged to 100% prior to install. Former battery was OEM sized and only 18 months old. Also a DieHard but 550CCA (small) battery.

Welcome from Boston.

Suspect if the problem is intermittant, you have not seen it yet. Do you have a modern battery tester? It will show you the battery condition in terms of amp-hours. This will tell you how large the drain was (starting minus ending divided by time) and give you a chance of catching the condition while it's happening.

Or, you could disconnect the battery and test over a couple of weeks. This may give you confidence that the battery is not defective.

Yes, an SI alternator can be a drain (the regulator in the alternator). BTDT. Hard to draw a conclusion with an intermittent problem and only a negative test (ie no result implies problem is gone); however, you could unplug the alternator and see if the problem goes away. You may need to disconnect the charge wire too.

[tgreese]

Mmm. Not a super-expert on the alternator electronics, but an alternator does not have a segmented commutator like a generator. The rotor is enegized through slip rings that conduct constant DC. The three section rotor rotates inside the three section stator and makes three-phase AC which is rectified to DC. Alternators replaced generators because of the semiconductor revolution - you can't economically make an alternator without solid state diodes that rectify the AC.

The charge wire should be isolated from the regulator and ground by the rectifier bridge (diodes) and a capacitor. The capacitor could be leaky, which would be a drain. Unlikely the diodes are shorted, though possible. Usually they work or go open, and that's not a common failure in the SIs AFAIK. The alternator plug has a sense wire and exciter. The exciter connects to the ignition switch and is shut off. The sense wire goes back to the battery and connects to the regulator internally, and normally has some small constant drain to ground.

The 10SI circuit diagram is shown in the TSM, if you are savvy to such things.

Amp-hours is approximately 1/7 the CCA; using 800 as the nominal CCA, that's 114 amp-hours times 13% divided by 72 hours is about 200 mA. Got to be going somewhere. I would repeat your experiment with the battery disconnected to rule out a defective battery.

If you have access to a thermal camera, you should be able to see the sink to ground. P=IV, 0.2*12 is 2.4 watts; I'd expect that to be detectable if the weather is cool and the air is still. Maybe try your laser thermometer if you have one, but it may not be precise enough. If you know any trades people like electricians or plumbers, they often have a thermal camera for their phone.

[tgreese]

Are you unsure about testing the current drain? You connect the meter between the battery and the battery cable - in series with the battery - so the parasitic current goes through the shunt in the meter. Disconnect the negative battery cable. The meter likely has a test lead socket for the amps range; that is, you move the positive test lead from the volts socket to the amps socket and select the amps range.

[tgreese]

Currently it's a lovely day and I have easy access to make such a test.

CurrentLeakageTest.jpg

This is a good meter, and it has a socket for amps (labeled "A" to the left of the red cable plug) and socket for milliamps and microamps (labled "mA/uA" which I have the red lead plugged into). The black lead is plugged into "common" which is common to all three red sockets (natch). This meter also has an alarm that sounds if you have the dial set wrong for the sockets you are using. Nice.

The amps socket is fused at 10 amps, and milli-microamps socket is fused at 200 mA. If you don't know what you'll get, you start with the 10A socket then go to the 200mA socket for better accuracy. No great disaster if you blow the fuse, but you won't be able to use the meter until you source and replace the fuse.

The meter dial here is set to the Amps/Milliamps setting. This meter also has a mode setting button, which is on DC. I used a clip lead because I don't have three hands; the positive meter lead goes to the clip lead which connects to the negative battery cable. I touch the battery negative post with the negative lead and read 3.58 mA. This is probably the current that the regulator constantly sends to ground.

Link to this meter if you are interested: https://www.amazon.com/EEVblog-BM235-Br ... B01JZ1ADCO

[BigNasty]

@Tim
Yeah, your calculations are correct and that is why I was concerned. Makes no sense.

Yes, I have done many a parasitic draw tests with a multimeter. In fact, I have a "fancy" tester that slips under the neg clamp so I can keep from disconnecting the clamp from the post. Normally it works perfectly and dead new batteries I can find them immediately. This one baffles me because the draw is so minimal. Tested another vehicle just to verify my meter was good. May borrow my neighbors to triple check.

I cannot say in words how much I appreciate your time helping on this. So puzzling. May have to reset my testing and start from the beginning...again. Assume my equipment is faulty and verify every piece before I test. Back to the shop.

[BigNasty]

Okay, so I retested everything. No change. Have pics of multimeter/ testing.

First, I installed the under clamp clip and the clamp clip from the parasitic test leads. Then cranked the truck, let it run for a few minutes to get the electric choke cycled. Shut it off and started the test by selecting Amps and set the test leads to 10A ports. Separated the clamp from the post and turned off the (test leads) bypass switch to run through the meter shunt. Got .005 amps.

Then, I switched the bypass back on, moved the leads to the mA port and selected the mA on the dial. Then switched the bypass off and get 6.65 mA reading. So both tests meet the same basic result.
Pics attached. So confused. May need a multi-day monitor to test this automatically over time and record all the data points for analysis. So frustrating. Not a spring chicken to automotive work, but this is kicking my ass.

[devildog80]

Yep.....have one kicking me too on my '84 GW. Pulled the neg battery cable between driving trips, until I installed a cutoff switch on the ground side. Keeps the hood closed, and simply shutoff the truck, then kill the neg connection off the battery. Resolved to look for this over the future years of owning the truck, as unable to currently find the problem, and more wiring to get redone before refresh completed. Figuring somewhere in the wiring tasks, will come across the problem, and will get fixed in the future.