Simple batt. drain test, [parasitic draw]
#1
Old Fart
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You will need a 12V test light, [not the LED type].
Start by undoing the batt. neg.(-) post make sure it is loose…
Attach test light ground clip to the batt. cable terminal and place the test light probe on the center of the post…
Carefully lift the clamp off the post making sure you do not touch the clamp to the test light probe…
The above is a lot easier if your not taking a pic.
If the test light does not turn on, you do not have a parasitic drain…
If on the other hand the test light does turn on, you do have a parasitic draw, how bright the light is will give you an idea of how bad the draw is…
On this one the light is very bright because the cars dome light and two pot lights were left on to simulate a parasitic draw, you would make sure everything is off before doing the test.
To find the circuit that is drawing current, leave the test light connected and start pulling fuses, [one by one] until the light goes out, when it does you have found the circuit that is “bad”.
Replace the fuse.
You would then disconnect, [one by one] anything that is fused by the fuse you pulled untill the test light goes out again. 94
Start by undoing the batt. neg.(-) post make sure it is loose…
Attach test light ground clip to the batt. cable terminal and place the test light probe on the center of the post…
Carefully lift the clamp off the post making sure you do not touch the clamp to the test light probe…
The above is a lot easier if your not taking a pic.
If the test light does not turn on, you do not have a parasitic drain…
If on the other hand the test light does turn on, you do have a parasitic draw, how bright the light is will give you an idea of how bad the draw is…
On this one the light is very bright because the cars dome light and two pot lights were left on to simulate a parasitic draw, you would make sure everything is off before doing the test.
To find the circuit that is drawing current, leave the test light connected and start pulling fuses, [one by one] until the light goes out, when it does you have found the circuit that is “bad”.
Replace the fuse.
You would then disconnect, [one by one] anything that is fused by the fuse you pulled untill the test light goes out again. 94
Last edited by fcm; 07-26-2011 at 03:59 PM. Reason: typo
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What is the threshold of drain to turn on the light? There is obviously some drain to keep alarms and memories alive. From what I remember, normal drain is under 50 mah. Another great explanation and photos, thanks.
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Old Fart
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I said, “You will need a 12V test light, [not the LED type].
I should have been more specific, [1-1.5A bulb, not low load bulbs or LEDs] I assumed most would know by looking at the test light in the last pic.
We use a 12V test light for parasitic drain tests on a daily bases.
You do not need to know any “threshold”, it does not matter how new the car is, you do not need to, “accurately measure a draw on a modern vehicle”, that’s the point…
Simple batt. drain test, [parasitic draw]
Let me explain in technical terms, maybe you can understand how it works and why it is so reliable, If the test light does not turn on, you do not have a parasitic drain
If on the other hand the test light does turn on, you do have a parasitic draw
If there is enough load on the batt. to turn on the test light, it is too high a load, what the load is, a trunk light that is “stuck” on in my 94 Integra or the GEM module of the 2011 Nissan V8 Titan, means diddlysquat, if the test light turns on it is too much if it does not it is not too much.
BTW, pic #3, “Carefully lift the clamp off the post making sure you do not touch the clamp to the test light probe”, is specifically for newer cars that have things like GEM modules that go to “sleep”, [power down].
Simple, right, [light on=problem, light off=no problem] the added benefit is the test light is also your “telltale” making finding the circuit with the problem and then the load on the circuit that is the problem, maybe like the 90 Grand Prix in the shop today with a broken power ant., [running constantly] less then 10min. to diagnose and repair, and not because you could hear power ant. motor, [unplugged the broken power ant.] or maybe the 2010, [that’s not too old is it?] Acura TL in the shop the other day, with a blend door motor staying on at the end of it’s travel, 15min to diagnose, [will be expensive to repair], it makes no differance.
Yes it is a “valid” test, and a simple one. 94
I should have been more specific, [1-1.5A bulb, not low load bulbs or LEDs] I assumed most would know by looking at the test light in the last pic.
We use a 12V test light for parasitic drain tests on a daily bases.
You do not need to know any “threshold”, it does not matter how new the car is, you do not need to, “accurately measure a draw on a modern vehicle”, that’s the point…
Simple batt. drain test, [parasitic draw]
Let me explain in technical terms, maybe you can understand how it works and why it is so reliable, If the test light does not turn on, you do not have a parasitic drain
If on the other hand the test light does turn on, you do have a parasitic draw
If there is enough load on the batt. to turn on the test light, it is too high a load, what the load is, a trunk light that is “stuck” on in my 94 Integra or the GEM module of the 2011 Nissan V8 Titan, means diddlysquat, if the test light turns on it is too much if it does not it is not too much.
BTW, pic #3, “Carefully lift the clamp off the post making sure you do not touch the clamp to the test light probe”, is specifically for newer cars that have things like GEM modules that go to “sleep”, [power down].
Simple, right, [light on=problem, light off=no problem] the added benefit is the test light is also your “telltale” making finding the circuit with the problem and then the load on the circuit that is the problem, maybe like the 90 Grand Prix in the shop today with a broken power ant., [running constantly] less then 10min. to diagnose and repair, and not because you could hear power ant. motor, [unplugged the broken power ant.] or maybe the 2010, [that’s not too old is it?] Acura TL in the shop the other day, with a blend door motor staying on at the end of it’s travel, 15min to diagnose, [will be expensive to repair], it makes no differance.
Yes it is a “valid” test, and a simple one. 94
Last edited by fcm; 07-29-2011 at 10:20 PM. Reason: typo
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#11
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If there is enough load on the batt. to turn on the test light, it is too high a load, what the load is, a trunk light that is “stuck” on in my 94 Integra or the GEM module of the 2011 Nissan V8 Titan, means diddlysquat, if the test light turns on it is too much if it does not it is not too much.
Simple, right, [light on=problem, light off=no problem] the added benefit is the test light is also your “telltale” making finding the circuit with the problem and then the load on the circuit that is the problem, maybe like the 90 Grand Prix in the shop today with a broken power ant., [running constantly] less then 10min. to diagnose and repair, and not because you could hear power ant. motor, [unplugged the broken power ant.] or maybe the 2010, [that’s not too old is it?] Acura TL in the shop the other day, with a blend door motor staying on at the end of it’s travel, 15min to diagnose, [will be expensive to repair], it makes no differance.
Yes it is a “valid” test, and a simple one. 94
Yes it is a “valid” test, and a simple one. 94
My correction was more for the benefit of anyone reading this thread. Do not use a test light when testing for a draw. It will invariably lead you down the wrong path and you will wind up looking for a problem that isnt there.
(*been there, done that)
Last edited by DCFIVER; 07-30-2011 at 10:20 AM.
#12
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So I guess all those cars with parasitic drain problems that we have “fixed” over the years using a 12V test light are not really fixed???
Let me guess, your an electrical engineer that works for a car manufacturer or a electronics test equipment manufacturers and your job is to make things a complicated as possible.
I do not understand why you can not grasp the concept that if there is enough draw to turn on the test light at all, there is too much draw, and if not the draw is acceptable.
It does not need to be “accurate” you only need to know if the light turns on or if it does not, I fail to understand how that would lead anyone “down the wrong path”???
I am pretty sure I have never said A/C systems absolutely do not leak,, leaking A/C systems is what keeps me in business and leak is a relative term, you consider a leak in an A/C system as anything, even if it takes 5+ years for it to effect the system where I on the other hand consider it a leak if it effects the system in less then 3 summers.
I have customers who think if it lasts a summer it’s not a leak big enough to worry about.
I posted this for the vast majority of car owners out there that do not have a multimeter or do not know how the use one properly or can’t afford one, but anyone can afford $1.99 for a cheap test light or already has one and know how it works
You need to stop discouraging people from using simple methods to diagnose/troubleshoot problems using simple tools that they most likely already have.
Instead of slamming my posts on how wrong I am, because that is all I see you doing, how about telling us all the “correct” way to go about it, but I get the feeling you read something someplace, and you assume it is gospel, you should stick to repairing smog issues because you know nothing about electrical issues. nuff said. 94
Let me guess, your an electrical engineer that works for a car manufacturer or a electronics test equipment manufacturers and your job is to make things a complicated as possible.
I do not understand why you can not grasp the concept that if there is enough draw to turn on the test light at all, there is too much draw, and if not the draw is acceptable.
It does not need to be “accurate” you only need to know if the light turns on or if it does not, I fail to understand how that would lead anyone “down the wrong path”???
I am pretty sure I have never said A/C systems absolutely do not leak,, leaking A/C systems is what keeps me in business and leak is a relative term, you consider a leak in an A/C system as anything, even if it takes 5+ years for it to effect the system where I on the other hand consider it a leak if it effects the system in less then 3 summers.
I have customers who think if it lasts a summer it’s not a leak big enough to worry about.
I posted this for the vast majority of car owners out there that do not have a multimeter or do not know how the use one properly or can’t afford one, but anyone can afford $1.99 for a cheap test light or already has one and know how it works
You need to stop discouraging people from using simple methods to diagnose/troubleshoot problems using simple tools that they most likely already have.
Instead of slamming my posts on how wrong I am, because that is all I see you doing, how about telling us all the “correct” way to go about it, but I get the feeling you read something someplace, and you assume it is gospel, you should stick to repairing smog issues because you know nothing about electrical issues. nuff said. 94
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Hard to get in the middle of this, but, trying to add a solution to quantify the draw. I originally asked about threshold because many cars are in the up to 50mah drain with their normal functions especially with aftermarket components and alarms. If you have a light that takes more than 50mah to turn it on, then this works fairly well. In addition, about 50mah x 24hr is 1.2 amps drain/day. My PC 680 holds about 16-20 amps, depending on draw rate, so some reserve. About half of the capacity gone will give a very weak battery. Batteries do not like to sit drained very far, so 50mah is a nice cutoff. Of course a multimeter on amp mode could be inserted instead of the light and a drain or parasitic amp number known. I think that the light certainly finds most problems, because they are not 75mah draw. A light on, or a short has a significant draw rate. Most, not all multimeters will measure the amperage.
Last edited by Drive 4 fun; 07-30-2011 at 01:13 PM. Reason: correction
#14
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So I guess all those cars with parasitic drain problems that we have “fixed” over the years using a 12V test light are not really fixed???
Let me guess, your an electrical engineer that works for a car manufacturer or a electronics test equipment manufacturers and your job is to make things a complicated as possible.
Let me guess, your an electrical engineer that works for a car manufacturer or a electronics test equipment manufacturers and your job is to make things a complicated as possible.
Instead of slamming my posts on how wrong I am, because that is all I see you doing, how about telling us all the “correct” way to go about it, but I get the feeling you read something someplace, and you assume it is gospel, you should stick to repairing smog issues because you know nothing about electrical issues. nuff said. 94
As for showing people the right way to test for a draw, I have already covered this. In depth. The search button is your friend.
#15
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Hard to get in the middle of this, but, trying to add a solution to quantify the draw. I originally asked about threshold because many cars are in the up to 50mah drain with their normal functions especially with aftermarket components and alarms. If you have a light that takes more than 50mah to turn it on, then this works fairly well. In addition, about 50mah x 24hr is 1.2 amps drain/day. My PC 680 holds about 16-20 amps, depending on draw rate, so some reserve. About half of the capacity gone will give a very weak battery. Batteries do not like to sit drained very far, so 50mah is a nice cutoff. Of course a multimeter on amp mode could be inserted instead of the light and a drain or parasitic amp number known. I think that the light certainly finds most problems, because they are not 75mah draw. A light on, or a short has a significant draw rate. Most, not all multimeters will measure the amperage.
Battery drain should not excced this number. An example: You have a battery with a RC of 100. 100/4 =25. So 25ma or less is an ideal draw for this battery.
* RC=reserve capacity.
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This is one of the many reasons why I stopped coming to this forum!
Everyone knows it all! Everyones correct! When is it going to stop?
If you don’t know how to correctly diagnose a car then don’t post it!
People come here to research and get CORRECT information not WRONG ones!
Its the year 2011 now! So stop fixing cars with a test light!!!!!!!!!!!!!!!!!!!!!!!
FCM: You sir are WRONG!!!!
DCFIVER: You sir are 100% correct!!!!
Everyone knows it all! Everyones correct! When is it going to stop?
If you don’t know how to correctly diagnose a car then don’t post it!
People come here to research and get CORRECT information not WRONG ones!
Its the year 2011 now! So stop fixing cars with a test light!!!!!!!!!!!!!!!!!!!!!!!
FCM: You sir are WRONG!!!!
DCFIVER: You sir are 100% correct!!!!
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lol the title of this thread clearly states “simple test”. Yes this is quick and simple, esp for older vehicles. I however prefer my fluke 87 for these types of things. Just fyi don’t go over 10a or it’ll cost ya 14 bucks for a new fuse.
#18
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So what part of “simple” do you guys not understand, this test is for someone without test equipment, they can do a simple test with a test light.
I do not care how new the car is, if it is 12V the test will work, it may not be definitive, it is just a simple basic test that someone that keeps running into a dead batt. can try and use to trace where the draw is.
This is what I do for a living, [Dave Ward Auto Electric] and yes, I have $5000 in test equipment for car electrical, but for a basic quick test the 12V test light works, we use it almost every day on all MM&Y of cars, if more testing is need then the $800 Fluke comes out, pretty sure most people on here do not have $800 multi meters or $2500 AVRs and so on.
How about we do not deprive someone of a simple test that could end up saving them 100s of dollars in diagnostic charges, because the the trunk light is staying on.
B18ek, if you do not like it here, don’t come back, simple. 94
BTW thanks for bumping the tread.
I do not care how new the car is, if it is 12V the test will work, it may not be definitive, it is just a simple basic test that someone that keeps running into a dead batt. can try and use to trace where the draw is.
This is what I do for a living, [Dave Ward Auto Electric] and yes, I have $5000 in test equipment for car electrical, but for a basic quick test the 12V test light works, we use it almost every day on all MM&Y of cars, if more testing is need then the $800 Fluke comes out, pretty sure most people on here do not have $800 multi meters or $2500 AVRs and so on.
How about we do not deprive someone of a simple test that could end up saving them 100s of dollars in diagnostic charges, because the the trunk light is staying on.
B18ek, if you do not like it here, don’t come back, simple. 94
BTW thanks for bumping the tread.
Last edited by fcm; 09-08-2011 at 05:30 PM. Reason: typo
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very straight forward test that is very commonly used. Good writeup, pics help for people that are visual learners.
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Both of you are correct to some extent…
I use a multimeter to watch current draw after the car goes to “sleep” I typically use .030 amps as the maximum for most models, but some of the larger and more electronically equipped models draw as much as .050 amps…And this is normal…
I think the argument here is “Will a 30 mA current draw turn on a test light?”
I do not know because I always use a multi-meter. BTW- I am also a technician at a German car dealership, so we have electrical issues ALL THE TIME, LOL… Makes me really appreciate my Honda
As DCFiver stated, this test is just fine on simple cars like mid/late 90’s Hondas.
I use a multimeter to watch current draw after the car goes to “sleep” I typically use .030 amps as the maximum for most models, but some of the larger and more electronically equipped models draw as much as .050 amps…And this is normal…
I think the argument here is “Will a 30 mA current draw turn on a test light?”
I do not know because I always use a multi-meter. BTW- I am also a technician at a German car dealership, so we have electrical issues ALL THE TIME, LOL… Makes me really appreciate my Honda
As DCFiver stated, this test is just fine on simple cars like mid/late 90’s Hondas.
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ok this is an old post but I need help I have the same test light but mine is red for hot…ok and green when I touch the neg….is this normal?? I did the same thing and the light stayed on the whole time……it was green not red(red indicating that is hot or has a draw) now my car is still dying after 3 days on a fully charged battery my starter is good alternator and battery is new maybe bout month old…idk what it could be any thoughts
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Don’t really know why the color of lights matter but I think it means you failed to identify the drain on the system.
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fml :/ I pulled all my fuses and the light stayed on…..literally I had all my fuses on the floor and it stayed on
