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

[Kern Dog]

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.

 

[Photon440]

Well, with everything turned off and you think there's nothing to draw power, put a volt meter between the cable and the battery ground post. If current shows up, at least you know you're chasing something.

 

[Kern Dog]

Well, with everything turned off and you think there's nothing to draw power, put a volt meter between the cable and the battery ground post. If current shows up, at least you know you're chasing something.

Between the negative terminal and the negative post on the battery? If they are connected, would there be a difference ?

 

[R413]

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!

 

[1 Wild R/T]

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.

Do you have an amp on the stereo?

 

[Kern Dog]

No, I do not.

 

[Kern Dog]

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 light goes out then the 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.

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!

Sometimes I have a hard time getting the point. Please bear with me on this.
You wrote "Remove one battery cable", I'm guessing it has to be the positive cable? Am I supposed to essentially bridge between the positive cable and the battery positive terminal using the test light ?

 

[1 Wild R/T]

No, I do not.

Well that eliminates a common draw...

Got a test light? If so disconnect the negative battery cable & attach the test light between the battery & the cable... If the light comes on you have a draw... Some minor electrical stuff like a radio memory will cause a very dim light but those types of draws take weeks to kill a good battery.... With the test light in the circuit briefly touch the cable to the battery post, the light will go out.... And depending on the draw it may not come back on once you pull the cable away from the post...

Your gonna wind up pulling fuses one at a time to see if the light goes out but you need to disable the dome light...

More to come..


I see I'm to slow....

 

[1 Wild R/T]

Sometimes I have a hard time getting the point. Please bear with me on this.
You wrote "Remove one battery cable", I'm guessing it has to be the positive cable? Am I supposed to essentially bridge between the positive cable and the battery positive terminal using the test light ?

I prefer the ground cable it's safer but either one will work.. Yes bridge the circuit..

 

[Kern Dog]

Thank you.
I often already know the answer to these things when they happen to someone else. For some strange reason, sometimes my mind goes blank when it happens to me.
Same thing goes for "no-spark" situations. I end up replacing parts until it starts. Good thing I have a supply of good used electrical parts from parting out so many cars!

 

[1 Wild R/T]

I prefer the ground cable it's safer but either one will work.. Yes bridge the circuit..

And I agree, remove the big wire from the alternator... And pull the cigarette lighter...

R413 has covered it pretty well..

 

[Photon440]

Between the negative terminal and the negative post on the battery? If they are connected, would there be a difference ?

I meant to take the terminal off the battery post and then use the meter to see if there was any current flowing between the post and terminal.

 

[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.

 

[mikedonz]

As I sit here at 2:30 am not being able to sleep, I want you guys to know what a blessing it is to learn from you. When I come across this problem in the future, I'll be able to fix it. But, like you Kern Dog, I probably wont remember!! Haha
Thanks guys!!

 

[Kern Dog]

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

 

[HALIFAXHOPS]

I hear you I walk away till I am into it again otherwise you miss the simple stuff.

 

[HALIFAXHOPS]

These are a great tool run them across dc wires and shows you which direction the draw is in, when you pass it it changes direction. Best troubleshooting tool I have for shorts.

 

[Mike67]

Kern if you have a DMM that will read DC amps , all you have to do is put your meter in series with the circuit.
Remove the fuse put one lead on one side of the fuse holder and the other on the other side. If you see a reading its on that circuit, & thats your culprit.

 

[DeltaV]

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.

Have the wife climb into the trunk and close the lid. She can confirm if the trunk light actually goes out. Then, let her out and give her a hug and kiss.

Also, have her jiggle the switch while the lid is closed.

 

[ddpsnake]

glove box light, btdt