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Old 08-06-2019, 09:44 PM   #1
Tinker
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Default Spark at Battery is it a short?

Okay so I've told I need start a thread... I guess.


Can someone explain why disconnecting a lead at the battery and you get sparks, is certainly a short. I can take a two leads and make a spark every time?



I have decent ford electrical knowledge. Just curious?


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Old 08-06-2019, 10:45 PM   #2
fortyonerag
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Default Re: Spark at Battery is it a short?

In this scenario something is drawing power from the battery. The spark is the interruption of supply.

If everything that might draw power is disconnected, lights off, electric clock & CD (if you have one) disconnected etc, etc, then something is drawing power through an inadvertent connection - short.
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Old 08-06-2019, 11:03 PM   #3
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Default Re: Spark at Battery is it a short?

So there is a amp draw. But why is that different then connecting two leads or a +/-, most times you get a spark off connecting poles directly? Most welders work on this principle.


Just don't think every time you disconnect a battery and it sparks its a positive indicator of a short... lead disruption is a disconnection of power (short).


On a system that has many components. shorts certainty is only known from a meter if there is draw. Not from a spark only... or not.



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Last edited by Tinker; 08-06-2019 at 11:44 PM.
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Old 08-07-2019, 05:13 AM   #4
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Default Re: Spark at Battery is it a short?

The amp draw will determine the intensity of the spark. No amp draw no spark. If you connect the + and - lead directly that is a short and a big spark because there is no resistance anywhere other than the wire itself. You are correct, this is how welders work, just huge amp draw and much higher voltage. Now, put a light bulb in between the leads, such as using a test light, and the bulb is the resistor to reduce amp draw and you will get a spark but not very intense. On the other hand if there is no amp draw that means there is no connection from the + to - poles of the battery anywhere in the system there will not be a spark. In other words, connecting a wire, that is not connected to anything else, to a battery will not produce a spark. So, if you get a spark you need to determine where the amp draw is. If it is intentional then you can switch that off and no issues. Otherwise there is a short or draw somewhere and even if it not an intense spark it will drain the battery.

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Old 08-07-2019, 06:12 AM   #5
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Default Re: Spark at Battery is it a short?

We are just going through this on a piece of equipment at work. Sometimes u cant even see the spark, but u can hear it, still a small short, or leakage to ground and it will drain the battery. most modern automotive radios, and possibly other components have a small draw built in for storing your settings, that's why it may take a month or more but it will drain your battery. Drive your car every few days, no problems
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Old 08-07-2019, 06:38 AM   #6
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Default Re: Spark at Battery is it a short?

Typical voltage regulator 'cut out' not opening on shut down??? Take the Bat wire off
the regulator and see it that sparks. Stupid things like I left my heater on low 'can't
really hear the fan and heater switch bulb is burnt out next day dead battery. Gotta
start disconnecting thing until you find it.
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Old 08-07-2019, 07:19 AM   #7
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Default Re: Spark at Battery is it a short?

A radio with a time display draws a little juice all the time to keep the clock correct. Like stated , I would check the aftermarket additions first... Chap
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Old 08-07-2019, 07:54 AM   #8
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Default Re: Spark at Battery is it a short?

Given the simplicity of our typical vintage automotive electrical system, this tells me that you either have something "ON" (drawing an amp load) or you have a short . . . also drawing an amp load. Given that you don't have a computer or anything that should be on, this situation will draw down your battery after some period of time. After you've checked the 'obvious' things (like brake light switch, lights, ignition switch, etc), then I'd be checking the components in my charging system.
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Old 08-07-2019, 08:22 AM   #9
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Default Re: Spark at Battery is it a short?

Quote:
Originally Posted by Tinker View Post
So there is a amp draw. But why is that different then connecting two leads or a +/-, most times you get a spark off connecting poles directly? Most welders work on this principle.


Just don't think every time you disconnect a battery and it sparks its a positive indicator of a short... lead disruption is a disconnection of power (short).


On a system that has many components. shorts certainty is only known from a meter if there is draw. Not from a spark only... or not.



.
If you get spark, you have current draw. Think of the spark as current you can see. No electrical load, no current, no spark

In an old car, if everything is off, and you get spark, something aint right.

If you bridge +/- on your battery, you will get spark, along with other more lively effects.
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Old 08-07-2019, 08:34 AM   #10
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Default Re: Spark at Battery is it a short?

Tinker, see if this helps. To get a spark you need a complete path from one battery post to the other post. When you directly touch the battery leads you have that path. With the car wiring, even though the system is "hot" in a lot of the wiring there is not a path to ground unless one is created. This could be a wire shorted to ground or a switch left on on say the lights or the ignition. It could be the cut-out stuck shut, etc. But unless there is a path to ground there is not going to be any current flow. If you check the battery lead with a meter you will not see any reading unless again there is a path to ground. The same current flow that would show up with a voltmeter is the current flow that would produce a spark.
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Old 08-07-2019, 11:45 AM   #11
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Default Re: Spark at Battery is it a short?

Old rubber case batteries would bleed voltage thru the bottom. Locomotive electrical systems did not use a ground, so you could have positive and negative leaks to chassis.


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Old 08-07-2019, 03:22 PM   #12
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Default Re: Spark at Battery is it a short?

A test light connected between the removed cable and battery is a good way to diagnose the draw . Have visual of test light and disconnect fuses or leads one at a time to find the culprit. If the light dims but is still on , keep that circuit disconnected. You would /could have more than one draw . I use to use GM door /key buzzers instead of the test light when I couldn't keep an eye on the test light
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Old 08-07-2019, 03:27 PM   #13
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Default Re: Spark at Battery is it a short?

I have a 6 volt turn signal buzzer that can be wired for testing circuits... Chap.
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Old 08-07-2019, 05:50 PM   #14
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Default Re: Spark at Battery is it a short?

Some of the old hard rubber battery cases had enough carbon in them to be able to slowly pass current but it was in the micro amp range so it still takes a long time to go dead. Modern plastic case batteries can set on what ever is handy as long as they don't leak electrolyte or get submerged in water.

The diesel electric locomotives have to be able to reverse the direction of rotation. They have grounds but they have to be switched to allow forward and reverse.

On modern cars, I pull one fuse at a time while monitoring the draw on the battery. When the current drops off, you've found the draw. The old cars sometimes don't even have fuses and many have short stop circuit breakers. On those, a person has to isolate one circuit at a time by disconnecting terminals.
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Old 08-08-2019, 05:38 AM   #15
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Default Re: Spark at Battery is it a short?

On my 32 the cut out on the generator stuck closed. Burned out the amp meter ! Just a side note, kx
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Old 08-08-2019, 08:01 AM   #16
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Default Re: Spark at Battery is it a short?

A friend had a non working radio that was in the ON position but since it made no noise, he wasn't aware that was where the draw was coming from. Like stated above either a short somewhere or something left on. Often the cutout or voltage regulator is the culprit. If the car is new enough to have courtesy light switches those are the ground side of the circuit and can be shorted also check the dome light socket.
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Old 08-08-2019, 06:05 PM   #17
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Default Re: Spark at Battery is it a short?

I must have had a small lapse of memory. Amps would certainly cause a spark. But my thinking was that it doesn't always mean a short for certain.


Thanks guys for all the clarification. Sorry to dumb things down for a bit. I do not get sparks on my old fords. New truck of course, computers and radio.



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Old 08-08-2019, 06:12 PM   #18
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Default Re: Spark at Battery is it a short?

Quote:
Originally Posted by Tinker View Post
I must have had a small lapse of memory. Amps would certainly cause a spark. But my thinking was that it doesn't always mean a short for certain.


Thanks guys for all the clarification. Sorry to dumb things down for a bit. I do not get sparks on my old fords. New truck of course, computers and radio.
Hay, just join the club. I can't count how may times I get my brain locked on one thought and it takes a while to resort my thinking! Then I wonder what the he** was I thinking!!
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Old 08-08-2019, 06:38 PM   #19
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Default Re: Spark at Battery is it a short?

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Hay, just join the club. I can't count how may times I get my brain locked on one thought and it takes a while to resort my thinking! Then I wonder what the he** was I thinking!!

JSeery does that mean I should give up working on old fords and take up golfing? hahaha just kidding. Thanks again.
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Old 08-08-2019, 07:38 PM   #20
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Default Re: Spark at Battery is it a short?

I would have the same problem with golf! There are good days and then other days.
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