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post #1 of 19 Old 04-19-2017, 10:43 AM Thread Starter
JFH
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Electrical Issue

I have a 2001 wrangler with a weird electrical issue. Ii seems that I have a parasitic draw in the electrical system. When I connect a test light between the battery negative cable and the negative battery post the test light pulsates from dim to bright. I have isolated the problem to the #15 IOD and the ACCESS fuse. When the test light is connected the gauges pulsate up and down in rhythm with the test light and it speeds up when I open either door which is also on the ACCESS circuit. The other thing is that it stops when I depress the brake pedal. I also removed the radio and sub woofer fuses but no change. I don't know if there's a relationship with a battery problem I am having but I have gone through three Excide battery's in the last year due to bar battery cells. I checked the battery voltage (12.4 volts) and alternator output while running at 1500 RPM's (14.02 volts).
If anyone has any ideas or thoughts on this issue please let me know.

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post #2 of 19 Old 04-19-2017, 11:45 AM
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A test light is not the best tool for this job. If you have access to an ammeter connect one to the negative battery cable in series. If the current draw is in excess of (if recall correctly) 60 milli amps you have a parasitic draw. But prior to drawing a conclusion make sure you allow for all systems to power down first ie pcm etc. A word of caution be aware you will be running current through your meter if it's excessive you may blow an internal fuse or damage the meter itself

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post #3 of 19 Old 04-19-2017, 11:48 AM
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You dont have to take the battery terminals off.... So DONT do what ^^^ said..

take the probes and wedge them in the battery terminals an set meter to 20 volts DC and watch the volts drop if there is a draw.
take a second to see but its far safer for the meter.
Then if its a large draw you can start pulling fuses till it stops dropping...

This is of course if your battery is good...
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post #4 of 19 Old 04-19-2017, 12:08 PM
elpaisa
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You're looking for current draw not voltage drop if your looking at a parasitic current draw issue. I've actually worked on vehicles for a living.

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post #5 of 19 Old 04-19-2017, 12:17 PM
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http://m.wikihow.com/Find-a-Parasiti...ry-Drain?amp=1

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post #6 of 19 Old 04-19-2017, 01:16 PM
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Quote:
Originally Posted by elpaisa View Post
You're looking for current draw not voltage drop if your looking at a parasitic current draw issue. I've actually worked on vehicles for a living.

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YAWN,,,,,....

I am a electronic engineer, finishing my Masters this summer....... So the way I told ya works and will not hurt a thing...

But do tell what all you work on as I dont care..
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post #7 of 19 Old 04-19-2017, 01:28 PM
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Quote:
Originally Posted by Jeepsr4me View Post
YAWN,,,,,....

I am a electronic engineer, finishing my Masters this summer....... So the way I told ya works and will not hurt a thing...

But do tell what all you work on as I dont care..
An electronic engineer that is unable to use proper grammer?

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post #8 of 19 Old 04-19-2017, 07:48 PM
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I have a pretty fair electronic education and have taught it at times. If I was looking for the cause of a mystery current draw causing the battery to be drained, I'd be looking for a current draw too, not a voltage drop.

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post #9 of 19 Old 04-19-2017, 09:31 PM
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Voltage drop is a not watching for battery voltage to reduce. It's to determine how much voltage a consumer (light bulb, solenoid, etc.) uses.

Watching the battery voltage reduce will only confirm you have an amp draw. DVOM in series and pulling fuses systematically is quick, easy, and will give you a definite direction to go. A wiring diagram would be immensely helpful as well.

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post #10 of 19 Old 04-20-2017, 09:54 AM
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I gave the safe way to test,... A draw is a draw... A battery is a pool... Any leaks and it drops. That drop will reduce the voltage.. .. Yes a battery has some SOME regenerating abilities but not if the draw is pulling enough to cause issues.. I have used this method many times. I have seen ****tards use they other way and blow the fuse in the meter or worse fry the meter completely..
There are more than a few ways to skin a cat.. I used a 25-06 once... Ruined the meat, but was quick.

So again, do it my way and you good to go and not have to take cables off......
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post #11 of 19 Old 04-20-2017, 11:05 AM
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What Jeepsr4me is suggesting is absolutely correct. Assuming you know the battery is good then the voltage on your battery will drop slowly over time (if it didn't you wouldn't be having a problem ). This will happen whether you have unwanted draw (parasitic) or typical draw (maintain radio clock etc). If your draw is "normal" the voltage will drop slower than if you have an abnormally high current draw.

However, the difference in this drop is certainly not easily calculated and may be difficult for the inexperienced to judge.

If you are trying to measure the actual draw to determine if it is normal or not then measuring the actual current draw is clearly the way to go. 40 or so milli-amps would be on the high side of normal in my experience, but would be acceptable. My '06 has just an 11.5mA draw but I have no "extras" installed.

The interesting thing here is that your test light is pulsing, and this is quite unusual. Does your internal light or dashboard lights pulse? I would think they must be or the test light itself is introducing the pulse.


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post #12 of 19 Old 04-20-2017, 11:26 AM
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I personally would not be putting a voltmeter on the battery to watch if the voltage dropped over time to see if there's an unwanted current drain. I certainly would not teach anyone to look for a parasitic current draw that way. I have too many years of troubleshooting issues in circuits far more complex than that to agree that method would be the best way to find the source of the parasitic current draw. If you have the electrical knowledge to know to insert an ammeter or MA meter in series with the battery to see what the current draw is and to see if it is excessive, you also know not to engage high current drawing devices like the starter which could definitely blow the meter. Like you wouldn't measure a 1500 volt circuit with a mechanical analog volt meter set on its 1.5 volt scale. Common sense on both.

Having isolated and fixed many parasitic current draws over the past 50 years, my best advice is to insert the meter set to its appropriate amperage setting in series with the battery. Then as suggested above, once you have determined/confirmed that you do indeed have an excessive current draw that is draining the battery, start pulling fuses until you find the circuit causing the excessive current draw and then you can focus on finding the problem that particular circuit. In some cases I pull all of the fuses first and then reinsert then remove them one at a time to avoid having all the circuits on and drawing current simultaneously. I've had to do this too many times to ever agree to that other method being a good way to find the root cause of a parasitic or excessive current draw.
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post #13 of 19 Old 04-20-2017, 04:10 PM
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The problem with studying a battery voltage to determine a parasitic drain is that battery voltage naturally drops over time and the older a battery is the faster it drops.
By the time we factor in a voltage drop rate being highly subjective to the rate of drain and that the harder to detect parasitic drains are often low level, it's difficult to make an accurate assessment of the data collected unless one does this regularly and is also pretty familiar with the state of the battery.

As a long time EET I too would hunt that current trail, but first I'd try to get lucky by checking to see if any underhood or glovebox lighting is staying on when it shouldn't. A smokin hot bulb in a freshly opened compartment generally means it was already on before you opened the door. Also check to see if any relays feel warm when they aren't being used. A relay coil can take many days to drain a battery but eventually it will. Good luck in this quest!

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post #14 of 19 Old 04-20-2017, 05:32 PM
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Another interesting way to isolate and measure a parasitic draw is to voltage drop test your fuses. You'll need to have your meter set to millivolts. You can then reference a chart for the size and capacity fuse that you tested. As long as you use the chart for the correct size fuse, this method is extremely accurate. You can find charts here

http://info.powerprobe.com/fusechartsdownload
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post #15 of 19 Old 04-20-2017, 06:10 PM
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Quote:
Originally Posted by Loukaps View Post
Another interesting way to isolate and measure a parasitic draw is to voltage drop test your fuses. You'll need to have your meter set to millivolts. You can then reference a chart for the size and capacity fuse that you tested. As long as you use the chart for the correct size fuse, this method is extremely accurate. You can find charts here

http://info.powerprobe.com/fusechartsdownload
That's accurate but only if you know what the current flow through the fuse is supposed to be. I don't know of any reference material in the factory service manual that explicitly says what current flow is normal through any of the fuses. When looking for a parasitic draw and you're experienced enough, you just know an excessive current flow when you see it on the meter. Like pornography, it's hard to define but you know it when you see it.

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