Trying to find the electrical draw that drains the battery...

[Builderguy]

Photon440
You are correct sir. I had it in my head the stuff I work on now that also uses power to hold the various computer memories, alarms, and pre-sets. I completely went blank on the original Borg electro-mechanical clocks. Good catch

 

[Builderguy]

Kern Dog
As far as your parasitic draw problem goes. My understanding and practice is that on newer vehicles anything over 100 milliamps in draw would need to be looked at. Your draw should be a less as you don't have all the fancy new gadgets
(GPS, satellite radio, and memory seats, mirrors, and pedals) that add more demand to the system. Less than 100 milliamp
draw and I would stop looking.

 

[Kern Dog]

I was thinking that since I only have the stereo and gauges that have both switched power and constant power wires, there should be almost no impact.

 

[RJRENTON]

Question out of curiosity...
Has anyone checked the diodes in the alternator? IF one of the diodes in the alternator has shorted, it will drain the battery thru the stator windings. Mopar's alternators (both original round back and the square back design) use a 3 phase full wave bridge rectifier circuit. If a diode short out internally, this will result in a high resistance circuit thru the remaining diodes and stator windings, draining the battery usually over nite or within a few hours. If the alternator is a Powermaster design (one wire) with an internal regulator, it may be possible for the same thing to occur, in addition to the internal regulator and rotor excitation circuit, similar to the GM's diode trio. Usually, alternator diodes fail open resulting in a loss of output capacity, where the capacity is reduced by half not one third. Just a thought.....
BOB RENTON

 

[Builderguy]

See post #4

 

[mopar 3 B]

In have always disconnected both battery terminals and connected an ohm meter in series.

 

[Chargerjase]

I have a buddy that lives in a tee pee....
No, he is NOT American Indian, he is a cheap ***.
When he does electrical work, he rarely turns off the power. I'm sure that he has shocked himself a few times.

Is he the guy that is too cheap to buy a meter, so cautiously touches the back of his hand onto a live circuit? I know the type.

 

[super-bee_ski]

Remove one batt cable, put a 12V test light between the loose cable end and battery post, if it dimly lights up there is a draw. Start pulling fuses one at a time until test light goes out then the draw circuit is identified.

If still lit up remove alt wire from bolt on post, don’t touch wrench or the loose wire on ground. Does light go out now? Bad alternator.

You could have a stuck horn relay or headlight motor problem, unplug them also.

Disconnect all your add on wires also, could have something bad making a draw.

Check the test light with every change and it will tell you when you found the draw when it is no longer dimly lit. Have fun!

Wow, sounds like a great check!

 

[super-bee_ski]

I think that when I get pissed, my reasoning takes a break. When I am level headed, I have an excellent memory.

Same here!

 

[Rafe Baker]

Thanks for the info working on 68 charger I just got checking all the electrical.

 

[racinguy25]

Great info about checking for low amp draws, I really learned something. But, my favorite post was the guy checking his chandelier install. Funniest video I can remember seeing, my favorite part is when he appears the second time AFTER falling and hits the lite. He must a great sense of humor because he let everybody see his mistake.

 

[Mike67]

Well, I think that I did find the problem last night. The map light was switched on.

Most newer electronic devices ( radios, ecu's) have capacitive storage that eliminates a constant draw.

 

[Builderguy]

Pretty good article explaining draw and has step by step aids:

https://no.co/blog/parasitic-draw

 

[EDWARD BASFORD]

I have had an intermittent problem with the battery losing a charge in my '70 Charger.
I've had 2 different batteries do the same thing.
The battery holds a charge just fine sometimes and other times, it runs down within a couple of days.
Intermittent problems like that are a pisser to diagnose.
When the key is off, I am not sure of anything that is drawing power. The stereo is supposed to have 2 power leads, one continuous and the other is only drawing electricity when the ignition switch is on.
The dome light is off, doors closed, trunk lid closed and somehow, the battery goes dead anyway.
The battery is in the trunk and is well grounded.
Engine block to battery.
Engine block to chassis.
Chassis to battery.

 

[EDWARD BASFORD]

Most newer electronic devices ( radios, ecu's) have capacitive storage that eliminates a constant draw.

 

[EDWARD BASFORD]

On 70 Dodge and Plymouth I always run 8 or 10 guage wire from alternator direct to battery as power goes thru dash before going to battery which is a constant problem. I usually bypass ammeter in dash. I usually connect wires at ammeter and not use it. This is usually done for running purposes. Ed from Pipersville Pa.

 

[383man]

Mike67 is right phantom drain test. Remove neg. term. Place DVM set on dc ma scale in series. So bulb is car in illustration. All stuff off doors closed ect. If you read .05 mA then drain is ok higher do as mike67 says start pulling fuses or unhooking added elect devices till it drops. That will id circuit.
Go to 2carpros to see a tutorial

Yep that's the best way to check for a draw. Use a digital amp meter and it should be no more then 50 mili-amps as these guys said. Newer cars you may have to wait up to 20 minutes for all computers to time out but not on a 70 Charger. If more then 50 mili-amps then do as they said and pull fuses and unhook alt output also to make sure no diodes are leaking. Just a process of eliminating all leads that are hot all the time that could cause a draw. Good luck to you as you know everyone here will help you. Ron

 

[383man]

With 28 years on the tool truck I sold a lot of multimeters. I sold a lot of replacements and fuses because of tech's checking amps and shorting them out. Good idea to test with a test light first. It let's you know if it's safe to hook up your multimeter.

I know a mistake I would make sometimes is since I used my Fluke in volts a lot when I went to amps you have to change a lead on the meter and sometimes I would forget to change the lead. Then I had the meter on amps but the pos test lead was still in the volt hole which it should not be as it should be switched to the amp hole on the meter. But if you hook the meter up as amps in series and still have the pos lead in the volt hole it would blow the Fluke meter fuse right away. Volts would still work but amps would not until the meter fuse was replaced. That's why I would buy 3 or 4 fuses and keep them in my toolbox just in case. I usually used my meter in the 10 to 15 amp scale first as I knew as long as I did not turn the key on I never had anything drawing enough to be more then 10 amps. If it was something like a fan stuck on I could hear that and would fix it first. And you would be looking for a draw with everything off so should be no reason to turn key on when testing with the Fluke hooked up on amps. Ron

 

[Kern Dog]

The map light.
It is funny and just like I wrote: As soon as I went out to the car, I remembered that that I have done this electrical diagnosing test several times in the past. My mind sometimes goes to a WTF mode and reasonable thoughts get pushed out.
I remember hearing that seeing a small spark when the cable is brushed along the terminal meant that there was some electrical draw, a bigger spark meant a bigger draw.
That makes sense. The test light did show a semi-dim glow to it.
I pulled the headlight door motor wire plug, no change.
Cigar lighter wire pulled, no difference.
Map light switch, there it is. NO light comes on. In fact, the map light is burned out. It did work before though. Maybe the intermittent drain was happening because I bumped the switch and since the light didn't come on, I didn't know. I am guessing that even with a bad bulb, the terminal still can draw power ?
I'm charging the battery again. Hopefully it will hold a charge again.

This wasn't the problem.
The problem persists. With a battery over 12.6 volts, the car spins over. Below 12.4, it drags like there is 20 to 1 compression!
I put the starter in in 2008. When the engine is cold, the starter doesn't spin that fast. When the engine is warm, it seems to spin faster. When the engine has been run awhile, it turns over slower but still enough to start. It never seems to crank over fast like I have heard other big block cars with the Denso mini starter. I am wondering if this starter is a contributing factor.
Last time I was going around with this problem, I found the map light to be A problem. It obviously is not THE problem.
I did not disconnect the alternator. It is charging. The voltage at the relay and battery is higher with the engine running. Can an alternator be bad if it is charging correctly ? Can a starter draw so much power that it drains a battery just by sitting? That makes no sense to me but who the heck knows. I have another new mini starter here to try. It requires unbolting and moving the header so I'd rather save that task for later if I can.
I am going back to square one tomorrow. Pulling the alternator wire, fuses and who knows what else. I have been intending on correcting a few errors with the wiring anyway. When I changed to these aftermarket gauges, some of the lighting wires got grouped together and connected to the wrong power feed. The trunk light only comes on with the key ON. The radio won't hold a memory.
Lots to do !
Maybe last time I quit looking too early and didn't

 

[Derwud]

Trunk mount Battery? Have you checked your cables?