The EASIEST way to test parasitic draw

[@classiccarmaintenance]

NOTE: If you have a modern car with electronics or accessories that need continuous power supply to not lose data and settings, you need to hook up these electronics and/or accessories to an external power source to power them before disconnecting the battery. Always first check your car's owners manual and your car accessories' owners manuals for instructions. However, it’s important to know that if you use an external power source, you won’t be able to tell if the parasitic draw comes from any of these hooked up accessories or electronics.

[@stevet603]

I disconnected the positive from the battery terminal to the fusebox at the battery terminal. I thought the problem might of been where the cable joins under the fusebox, but couldn't figure out how to remove the box to inspect the underneath. I think I have an alternator issue, because as soon as I squirted some (lots) of WD into it the multimeter started reading milliamps instead of amps. A couple of days left overnight the battery showed as 12.68V so thought I had tracked it down, but today it was down to 12.35V (after locking up and leaving for an hour).

[@classiccarmaintenance]

@@stevet603 WD40 is an insulator fluid, meaning that it can temporarily solve an issue with an internal short somewhere in your alternator. If the WD40 fluid gets in between two rubbing wires or a damaged wire and a metal surface which cause the short/parasitic draw, it can temporarily solve/mask that issue. The first and easiest thing you can do to see if you have an alternator issue, is to disconnect your alternator right after having measured your car battery voltage. Then leave your car locked overnight with all electronics turned off, and measure the battery voltage again in the morning. If your battery voltage is much lower than the previous day, your alternator probably isn’t the (main) cause. If your car battery reads about the same voltage, it’s highly likely your alternator is faulty and needs to be replaced. In case this test indicates that your alternator isn’t the (main) issue, the next thing on your checklist, based on your findings, should probably be to find a way to disconnect and test the cable between the battery terminal and the fusebox. IMPORTANT: Do not attempt to start or drive your vehicle while your alternator is disconnected, as this could damage your alternator!

[@stevet603]

@@classiccarmaintenance Thanks for that. some days, it holds 12.6V, other day down to 8V overnight. where do I disconnect the alernator please?

[@classiccarmaintenance]

​@@stevet603 Disconnect all electrical wires that connect to the alternator, but make sure to first take pictures so you can reconnect them exactly as they were afterwards. Careful: do not start the engine or drive your car with the alternator wires disconnected to prevent damaging your alternator.

[@stevet603]

@@classiccarmaintenance Thanks again :) looks like I have to dismantle other bits to get to the connections :(

[@mark-1rc502]

Thank you for the most easiest non tech nerd way of explaining how to do it . 🙏

[@classiccarmaintenance]

Thrilled to hear you found it easy to follow! Thanks for the support and happy motoring!

[@tonymaxwell9460]

Hell yea!! Finally, a video I can understand. Thank you!

[@classiccarmaintenance]

You're welcome! Glad you liked it!

[@jerrydavis6995]

​@@classiccarmaintenance@classiccarmaintenance I

[@jmer3536]

This is the best Ive seen explaining what a parasitic draw is AND how to find it with a Multimeter

[@classiccarmaintenance]

Thank you, appreciate it!

[@PersonalRobotJesus]

Y'all consistently put out the best, easiest to follow DIY vids for auto maintenance I've ever seen. Thanks for keeping it simple and direct!

[@classiccarmaintenance]

Thanks so much for your support! Really appreciate it. It keeps us motivated to hear feedback like this. We'll definitely keep the videos coming. Great to have you on board!

[@razvanandreiparamon7762]

Thanks man, really helpful and straightforward

[@classiccarmaintenance]

You're welcome! Glad you liked it!

[@TheHighPriestessStudio]

This was so educational and I have no idea about vehicles except how to drive them but I had an alternator put in in 2024 in July and I’ve gone through three batteries since having that installed, and that’s not counting the multitude times of having to get the car jumpstart. I thought the NRMA were selling me faulty batteries. And no matter what happened I would always come out to find the car either taking forever to start or not starting at all. As it turned out, it’s the alternator that the auto electrician installed. Because they did a test and found nothing else draining the power. But I’m going to keep a check on this anyway because I’ve just got a new alternator put in so fingers crossed.

[@foggymtnbreakdown]

Your meter may confuse some viewers who have a different meter. On your meter, the switch is turned to the symbol for AC amps, which has the sine wave line under the solid line, but the digital display shows DC amps, which has the symbol with the dashed straight line under the solid line. I have 3 multimeters where the rotary switch can be set to DC amps or AC amps. If I did it like you did it on the video, I would be trying to measure AC amps instead of DC amps. I am assuming that the "func" button on your meter selects between AC amps and DC amps. Your video helped me a lot. Thanks for taking the time to post it!

[@classiccarmaintenance]

You are correct! Our multimeter has a single symbol for both AC and DC amps, which we can switch between by pressing the FUNC button. If you have a multimeter with seperate symbols on the rotary switch, you have to turn it to the DC symbol with the dashed straight line under the solid straight line. Thanks for the feedback!

[@ThadeousMonkey]

Thank you!!! I watched several videos for this and you best described what to do and what to look for.

[@classiccarmaintenance]

Glad you liked it!

[@championsartain3061]

What a fantastic video. Thank you very much for this good sir! Twas informative and concise, I evn got a feeling of sense of humor. Great articulation and teaching presence. A++

[@classiccarmaintenance]

Thank you for the kind words, appreciate it!

[@Snoop3x]

You, sir, are a scholar and a gentleman. Thank you

[@classiccarmaintenance]

Thanks, appreciate it!

[@bobkernahan6340]

great video and to the point thank you

[@classiccarmaintenance]

Thanks, appreciate it!

[@HughDuncan-od8sq]

Beautifully done, thank you, now consider myself an expert in parasitic draw...

[@classiccarmaintenance]

Thanks! Glad you liked it!

[@alext8828]

Excellent video. Very clearly explained.

[@classiccarmaintenance]

Glad you liked it!

[@samkalma8268]

That was the easiest to understand 12v video I've ever watched thanks

[@classiccarmaintenance]

Glad you liked it, thanks for watching!

[@jackflash5659]

Very considerate to highlight the importance of safety at the beginning of this video. Terrific tutorial. To the point without any b.s. Liked and subscribed. Thank you and keep up the good work!

[@classiccarmaintenance]

Thank you for the support, it means a lot!

[@KC9IUX17]

No change up, no curveball, nothing but FUCKIN GAS GOAT

[@tnoiset9085]

Yay on the TJ! My battery has been going dead on my TJ after a few days of not driving it, which brought me to this video. I found where someone, through the years, had a couple of wires jammed into a couple of fuses/slots. Guess I am about to find out what those powered, hopefully nothing important, and perhaps my issue will go away. If not, you gave the perfect solution. Thank You!

[@classiccarmaintenance]

Glad you liked it! Thanks for watching!

[@billseka4141]

Excellent video !

[@classiccarmaintenance]

Thanks, appreciate it!

[@ballhawk387]

Right to the point, excellent!

[@classiccarmaintenance]

Thanks! Appreciate it!

[@bridgetlg]

Excellent and simple explanation Thanks. I needed quick a refresher course

[@classiccarmaintenance]

Glad you found it helpful! Thanks for watching!

[@tonebone2895]

How does the radio turn on with the negative terminal disconnected?

[@classiccarmaintenance]

When you hook up the multimeter between the negative battery terminal and the black battery cable, it functions as a bridge allowing power through. This, however, is limited by your multimeters' internal fuse(s). If you turn on too much electrical stuff and draw too much power, its fuse(s) will blow and you'll have to replace them.

[@tonebone2895]

Gotcha, thanks for the reply!​@@classiccarmaintenance

[@ronaldochambers1107]

An excellent video, brief but detailed. I understand with modern cars with their numerous computers it's even better to check for any voltage drop across a fuse using a second multimeter across the small terminals on each fuse. Thus the fuses are not removed which could "wake up" any computers which take a while to "go to sleep" when the fuse is replaced.

[@classiccarmaintenance]

Hi, Thanks for your reply, appreciate it! You’re absolutely right that there are other ways to test for parasitic draw, like measuring and investigating the relation between voltage drop and current draw by testing over the fuses while in situ. However, this involves testing and calibrating your test equipment before you start, researching “normal” power consumption of each circuit on your specific vehicle (taking into account aftermarket equipment), closing or latching all door locks and avoiding anything that might trigger a sensor that could “wake up” the car’s computer(s). To be absolutely sure that the computer(s) are “asleep”, with the latest cars you might have to wait up to 2 hours. To interpret the readings you get over the fuses, you would have to use a comparison chart, specific to the type of OEM fuses that are used in your vehicle. Aftermarket (replacement) fuses that often look exactly like the OEM ones might give different values and will be hard to guesstimate. That being said, these tests are very specific to the brand and model of your vehicle and to do it right, you need access to the correct information and experience with this exact type or family of vehicles. Our aim is to empower people on how to do a basic DIY test for parasitic draw that anyone can do, with a small budget using a simple cheap multimeter, without needing expensive equipment. Although it’s a basic test, and it may not be perfect, it gets the job done and it will eliminate all major parasitic draws in minutes.

[@alext6157]

Maaan I watched more then 10 videos about this and I couldn’t understand why the heck my meter would show 0 on 3 different cars. Now I checked my fuses, both of them are gone. But I already ordered a pro meter anyway😄. Thank you so much!

[@classiccarmaintenance]

Glad you liked it, thanks for watching!

[@jameswalley7234]

I had to open my door to get to the fuses, which jumps the lights and then waited for them to stop to get an accurate reading. I pulled a fuse for my seat and saw a change but after putting the fuse back the reading was normal.

[@greglonnon]

lead clamps and putting the meter on the windshield is a great idea. Thanks!

[@classiccarmaintenance]

You're welcome. Thanks for watching!

[@andrewmohammed9985]

Finally a video that helps

[@classiccarmaintenance]

Glad you liked it!

[@caznilo33]

Best video in a while

[@classiccarmaintenance]

Glad you liked it!

[@TheHighPriestessStudio]

This was so educational and I have no idea that vehicles but I had an alternator put in in 2024 in July and I’ve gone through three batteries since having that installed, and that’s not counting the multitude times of having to get the car jumpstart. I thought the NRMA were selling me faulty batteries. And no matter what happened I would always come out to find the car either taking forever to start or not starting at all. As it turned out, it’s the alternator that the auto electrician installed. Because they did a test and found nothing else draining the power. But I’m going to keep a check on this anyway because I’ve just got a new alternator put in so fingers crossed. Can I just ask and this might sound stupid but I am when it comes to cars mechanics. When you locate the area that is the problem with those fuse do you just have to replace that fuse to fix the problem or would it be something else?

[@classiccarmaintenance]

No, the fuse itself isn’t the problem. Pulling the fuses is just a way to easily locate on which circuit the parasitic draw is located. If you pull the fuse that protects the radio only, for example, and the parasitic draw disappears, you know the radio or its wiring is causing a parasitic draw. The radio might not be switched off, as shown in our simulation, or there might be a damaged wire, or the radio itself might be faulty. Once you’ve determined by elimination which part(s) is (are) causing a parasitic draw, you know what needs to be repaired or replaced.

[@markw96789]

Thank you for your reply. I have watched your video many times. Will continue to trace my gremlins. How can one determine if the draw is caused by a faulty ground somewhere. I there a way to test the ground ??? With a multi meter ?? Thank you very much for actually responding. Most don’t. I am grateful for you time and advice

[@classiccarmaintenance]

You’re welcome! There’s no such thing as a parasitic draw from a “faulty” ground. A faulty ground means there is a bad connection between the electrical component (e.g. radio, lamp, horn,…) and the ground (meaning any bare metal part of the car or negative wire). As a result, the component will malfunction or not function at all. This however does not cause a parasitic draw. A parasitic draw results from the (positive) wiring contacting any metal parts or negative ground wiring, an internal fault in a device or a device or lamp that stays on after the contact is switched off. That’s why you have to test fuse by fuse to determine where the draw is situated. Once you’ve pin-pointed the problem, you can fix it. This however can sometimes be hard to find if a (positive) cables’ insulation is damaged and it contacts the ground (any metal part or negative wire) somewhere behind the dashboard for example. Worst case scenario, while testing for a damaged cable, the cable slightly moves and loses its connection with the ground, temporarily making the parasitic draw go away and undetectable. In this worst case scenario, a visual inspection of all cable insulation is needed. Any damaged or melted wiring should be replaced.

[@markw96789]

@ thank you very much for taking time to explain in detail for me. I truly appreciate your help. But if there is a loose or faulty ground from the car chassis what other issues might result??? Could something like that cause the battery to draw down over night ?? Or is any battery draw going to be caused by issues with positive wires being grounded like you describe or a component being faulty or switch staying open??? Last question if I may please ?? If a relay is faulty (Burnt) or shorted out could that faulty relay cause a parasitic draw ?? Thank you so very much Mark Ward

[@classiccarmaintenance]

If a ground is loose or faulty, the affected electrical component will either not work at all (e.g. ground disconnected and the component does not receive power) or not work properly (e.g. a corroded headlight connection that only delivers 8V while the component needs 12V, causing one of the headlights not to shine at full brightness). A loose or faulty ground however, cannot cause a power draw and will not drain your battery. A parasitic draw results from the (positive) wiring contacting any metal parts or negative ground wiring, an internal fault in a device or a device or lamp that stays on after the contact is switched off. A relay can also cause a parasitic draw either at the primary or secondary circuit. If there’s a short circuit in the primary circuit, this can generate heat which causes a small parasitic draw that drains the car battery. The secondary circuit, a contact that allows power to go to a powerful electrical component when it’s closed (e.g. to the headlights) can also cause a parasitic drain when it shorts internally. This can cause 3 different scenarios that will cause your battery to drain: the component stays on permanently, it only functions partially or it will not work at all. If the component doesn’t work at all when it’s switched on, with a faulty secondary circuit in your relay, it can still generate enough internal heat in the relay to get a parasitic draw. While the first two scenarios are easy to diagnose (always on or not functioning properly) the last scenario is the least likely but often overlooked because one assumes that a component that is not working does not draw power. While the component is not drawing power, the internal secondary circuit of the relay can be causing a parasitic draw. So in short: Sure, a relay can cause a parasitic draw, and the easiest way to find out is to test the fuses in your fuse box(es) like we showed in our video. Then you’ll know where to look.

[@ElGatoTerco]

Wow, dude thank you soo much! This video was simple! Now once I find the part of the wiring that has a draw, I'll just have to fenagle with it to find it. In my case, I'm fairly certain the '01 wrangler I just bought has some wires shorting out from some aftermarket headlights it used to have.

[@classiccarmaintenance]

Thank you, appreciate it!

[@scheuerle2]

Thank you for this!

[@classiccarmaintenance]

You're welcome, thanks for watching!

[@67marlins]

This is a very good post.

[@classiccarmaintenance]

Thanks, glad you liked it!

[@kennydiel4797]

Great video, simple to the point. Easy to understand. Finally not all the hoo-ha bla bla bla stuff.

[@classiccarmaintenance]

Thanks a lot! Glad you enjoyed the straightforward approach. Appreciate your support!

[@JeffBowe]

Clamping the leads was the best idea in the video!

[@classiccarmaintenance]

Glad you liked it!

[@CalebHigginbotham]

very informative and condensed video. thanks!

[@classiccarmaintenance]

Thanks! Glad you liked it!

[@trotion]

Very informative video, good work! Helped me

[@classiccarmaintenance]

Glad you liked it! More to come, stay tuned.

[@Shadybiz1]

Thank you for the video! Just bought a new (to me) car a month ago. Pretty darn sure that there is a parasitic draw, most likely because of the stock radio. Just ordered one of these, so I'll know for sure soon enough!

[@classiccarmaintenance]

Glad you found the video helpful! Sounds like you're on the right track. Good luck with the test, hope you get it sorted out quickly!

[@Shadybiz1]

@@classiccarmaintenance Oh I'm on the right track alright...on the right track to justifying the purchase of a new head unit and a new amp to replace the stock ones of each!! (...I was going to do that anyway, :))

[@classiccarmaintenance]

Sounds like a perfect excuse to upgrade! 😄 New gear always makes the project more fun, enjoy the new setup!

[@sydneymack8123]

Thanks for making that simple

[@classiccarmaintenance]

Glad you liked it, thanks for watching!

[@rolanddejesus8685]

thank you very much sir , very clear explanation.

[@classiccarmaintenance]

You're very welcome! Glad the explanation was clear for you!

[@NeaveConstantine]

Thank you

[@classiccarmaintenance]

You're welcome, thanks for watching!

[@siarlbychan]

Excellent! Straight to the point. Thank you. I had never heard of parasitic draw before today. I just purchased a 2019 RAM 1500. This is the first vehicle I've ever owned that has this much electronics. I love it but I also love my 1989 Toyota pick up. I can replace every part under the hood and see everything. So after turning off the ignition in the Ram 1500 I have noticed that things are still happening under the front dash. Humming, ports opening closing because of the Star Wars-ish whoosh (no exaggeration). It sounds like the opening and closing of the doors on the Death Star. So it made me wonder about power usage when the battery is not being charged. Every time I open a door, lights come on, the screen comes on, and they stay on for what seems a minute or so. So it's got to be a drain at some point right? Doing research today, I found out that it is called parasitic draw and there's an allowable amount of it! I wish it was zero. I'm old school and very utilitarian. I like all the bells and whistles but let's not get crazy. Thanks for the video!

[@classiccarmaintenance]

Thanks a lot! Glad you found it useful.

[@DesiCulture.007]

Great, which fuse it is is found but how to fix v the current problem that is being drawn still.

[@classiccarmaintenance]

Now you know which circuit the parasitic draw is located on, you can start to narrow it down further. You want to check the circuit for damaged wiring, or an electric device/component that might be faulty. Once you’ve determined by elimination what is causing the parasitic draw on that fused circuit, you now know what needs to be repaired or replaced to eliminate the parasitic draw.

[@user-sm8wo3dj5z]

Só you wait 30 min. As soon as you Touch the terminals with the multímetro, wont the car ECU wake up? Or only if you unlock doors? My w203 is drawing 4 amps

[@classiccarmaintenance]

No, the cars’ ECU won’t wake up from using the multimeter, but it will wake up from opening doors which triggers the door sensor.

[@NerdNerfer]

So, connecting the multimeter leads to the negative battery cable and negative post create the current when the negative cable is off? I tried this on my Ford Explorer and it was a constant ready of 30 mA. No changes. The battery dies over a day or two depending on whether I drove it a long time for a longer charge. I let it sit for 15 minutes and there was no change on the meter. This suggests there is not drain and everything is normal right? But that's not true, something is draining it. Thoughts?

[@classiccarmaintenance]

That’s correct, the multimeter leads form a bridge between the negative battery cable and negative battery post allowing power through. Any draw below 50 milliamps is normal and should not drain a healthy battery. If your battery keeps dying without a parasitic draw, either your alternator isn’t charging properly anymore causing your battery to drain while driving, or your battery itself is bad and can’t hold its voltage anymore. We have videos about how to test both your alternator and your battery, so make sure to check them out, it’s super easy! How to test your alternator with a multimeter: kzbin.info/www/bejne/bZKqg6asZdijgcU How to test your car battery: kzbin.info/www/bejne/fZaofqWGhK5jrq8

[@NerdNerfer]

@@classiccarmaintenance Ended up using a clamp meter from a neighbor that worked SUPER well to see the draw real time without worrying about the cables. Was able to pull fuses til I found the right one. Ended up being a SJB, which is not the best answer but an answer.

[@MrJames-cr6lu]

That for the information, sir!

[@classiccarmaintenance]

You're welcome, thanks for watching!

[@Ruudvancan1]

2019 Nissan Armada - I have ran through 4 batteries in 4 years. Every battery I get, only lasts a year. Took it to a mechanic 3 years ago who could not figure out why; Autozone had the battery charged up for me a month ago - still had issues starting a week after. A shop said 2 weeks ago that battery, starter, and alternator all tested good. As of yesterday, still struggles to start. Any advice, opinions, guidance would be helpful. I will perform this test when I get home this afternoon. Cheers

[@classiccarmaintenance]

Unfortunately, this is a known and well documented issue with the 2019 Nissan Armada. Batteries drain and need to be replaced after a year or so without an obvious reason. Some won’t even start without a jump starter. If you can’t find a parasitic drain performing our test, we recommend contacting a Nissan dealer for a complete diagnostic test.

[@Mike-yq6jg]

I have a 1990 g wagon and when I turn the lights on the side indicators have a slight glow ,any idea

[@stevenwillis7937]

How are you turning radio on when ground is unhooked

[@classiccarmaintenance]

When you hook up the multimeter between the negative battery terminal and the black battery cable, it functions as a bridge allowing power through. This, however, is limited by your multimeters' internal fuse(s). If you turn on too much electrical stuff and draw too much power, its fuse(s) will blow and you'll have to replace them.

[@woodstream6137]

I have a hybrid. My 12v is above the passenger rear tire

[@markw96789]

How do you determine if the parasitic draw is caused by a ground problem??? Broken or disconnected ground strap somewhere??? Please help

[@MS-kf5rr]

Thanks for the knowledge.

[@classiccarmaintenance]

Appreciate it! Thanks for watching.

[@DabbleDAM]

I have a multimeter but It doesn’t really match yours and I don’t know why symbol to use to test with mine. Anyone have some sort of guide to know whether I can even use mine and what to set it to?

[@classiccarmaintenance]

On most multimeters, you need to select the DC Amps setting. This symbol consists of an A (for amps) with a dashed straight line under a solid straight line (symbol for DC).

[@YOU_CONDUIT]

Do I need to unhook both negative sides on my battery’s if I have 2 batteries in my diesel?

[@classiccarmaintenance]

If your vehicle has 2 batteries that are set up in a parallel or series configuration, you only need to unhook the black (negative) cable that runs to the ground/chassis and place your multimeter in between that negative battery terminal and black (negative) battery cable, without disconnecting the battery cables that connect both batteries. If you have 1 battery for your engine and a separate one for your auxiliary power and accessories, you need to test the batteries one by one. First do the test with 1 battery and its corresponding fuses, and then the other with its fuses.

[@Ken-gv2ql]

The battery in my car is in the trunk. Could I run long wires from the battery (one wire on the red terminal and another wire on the disconnected black cable) to the multimeter which would be held near each fuse box?

[@classiccarmaintenance]

You sure can! This will speed up the process of finding the right fuse(s) as you don't need to run back and forth to view your multimeters' readings. But watch out: you mentioned connecting the multimeter between the positive (red) terminal and the disconnected negative (black) cable, which is incorrect. You need to connect the multimeter to the disconnected negative (black) battery cable with one probe and to the negative (black) battery terminal with the other probe, otherwise the test won't work.

[@Ken-gv2ql]

@@classiccarmaintenance Thanks for the help. I should pay more attention😀

[@jennypenny812]

Thanks for the video, I had a question. My car seems to short circuit when it rains, lights go crazy, Locks click on and off on their own, and even the trunk opens on its own, and this drains the battery, last time it killed it completely. I have a mini cooper r56 2009. Will this also work for my situation? I am guessing I have to wait till the car gets wet and the symptoms are showing, since when the car is dry, none of this happens... any tips? Thanks

[@classiccarmaintenance]

No, this probably won’t work because it seems like lots of different electronics start acting weird randomly, and it’s unlikely that all these different circuits are malfunctioning because of the rain. It rather sounds like your cars’ computer, which controls all these electronics, is short-circuiting or flipping because of false input or overload. This may be caused by your car computers’ connector plugs or one or more sensors not being waterproof and causing short circuits when they get wet. You could first try to clean the connector plugs with contact cleaner and put dielectric grease in the contacts to keep the water out and prevent further short circuits and oxidation. As a consequence of disconnecting your cars’ computer(s), your saved computer settings might be lost and might need to be reset.

[@tubetime39]

I show zero Amps but wondering if on volts setting should I see 12 v ?

[@classiccarmaintenance]

There’s something wrong if your multimeter shows 0 amps in the (DC) amps setting with the negative (black) battery cable disconnected from the battery post, and the tester leads between the negative battery terminal and the black battery cable. A 0 reading means there’s something wrong with your multimeter or the positive battery connection as there will always be a tiny amp draw somewhere because a cars’ electric wiring is never perfect. Normal readings should be anywhere between a few milliamps and 50 milliamps. When you test for voltage between the battery terminals with your multimeter in the DC voltage setting, a normal value would be between 12.4V and 14V (freshly disconnected from a charger).

[@max-tl1dr]

Thank you for this video. I have the same meter. I have been having trouble with intermittent battery drain on my 2015 civic. It happens randomly where I go out to the car and there is no power and I have to jump the battery. I did this test and it read 0.012 which I believe is in normal range right? I pulled some fuses anyway and when I pulled the "backup" fuse the meter went down to 0. There was no draw at all from the battery. Is this normal?

[@classiccarmaintenance]

Any draw under 50 miliamps is considered normal, so it appears that your conclusion that you don't have a parasitic draw is correct. If your car battery can't hold its' voltage but you don't have a parasitic draw, most likely your battery is bad and needs replacing. To make sure, check out our video about how to test your car battery which you can find on our channel: kzbin.info/www/bejne/fZaofqWGhK5jrq8. If your car battery passes the battery tests though, you might want to investigate your cars' electronics and car computer for erratic activity. If it turns on and off randomly for example, that might cause the occasional parasitic draw you're describing. In this case you might want to consult a certified Honda technician to sort out possible software-related issues.

[@curtstark4482]

It looks like you switched up the posstive and negative probes when getting the zero to explain a faulty reader. Can u explain thank you

[@classiccarmaintenance]

Switching the positive and negative test leads will only change the "direction" electricity flows through the multimeter, displaying the parasitic draw as a positive or negative number. It does not change the measured value itself. If you connect the multimeter between the negative battery terminal and the battery cable with the black test lead on the battery terminal, it will display the parasitic draw as a positive number. Put the red test lead on the negative battery terminal and the black test lead on the battery cable and it will show the exact same parasitic draw, but as a negative number with a "-" sign in front of it.

[@albertoguerra3995]

So what do you do now do I change the fuse with a new one or buy new radio?

[@classiccarmaintenance]

No, the fuse itself isn’t the problem. Pulling the fuses is just a way to easily locate on which circuit the parasitic draw is located. If you pull the fuse that protects the radio only, for example, and the parasitic draw disappears, you know the radio or its wiring is causing a parasitic draw. The radio might not be switched off, as shown in our simulation, or there might be a damaged wire, or the radio itself might be faulty. Once you’ve determined by elimination which part(s) is(are) causing a parasitic draw, you know what needs to be repaired or replaced.

[@markw96789]

Having trouble with a 2009 Acura TL. Numerous Alternator changes and battery changes. Can you help me please.

[@classiccarmaintenance]

If you changed the alternator and battery multiple times, I’m going to assume your issue is that your battery keeps dying which is usually caused by a parasitic draw. You should start by following the instructions in the video to determine if you have a parasitic draw and where it is located. Once you know where to look, you can start looking for a solution. It might be as simple as a glove box light or trunk light that does not turn off when closed! The simplest way to find out is to do the test as shown in our video.

[@TheStoryof6strings]

I still have and use that same radio!

[@veronicamartinez774]

I am confused he found where it is but how was it fixed. New fuse??

[@classiccarmaintenance]

As shown in our video, there was no actual parasitic draw in the car we tested. For demonstrational purposes only, we simulated a draw by turning the key to the auxiliary position with the radio on. The radio then draws power which can be measured with a multimeter just like it would in case you had a real parasitic draw. Once you know on which circuit the parasitic draw is located by elimination, you can narrow it down further. You want to check the circuit for damaged wiring, or an electrical device/component that might be faulty. Once you’ve determined what is causing the parasitic draw on that particular fused circuit, you now know what needs to be repaired or replaced to eliminate the parasitic draw.

[@davidlamb2538]

Great Great video. Thank you!

[@classiccarmaintenance]

You're welcome!

[@LKahlilR]

What if you need a certian accessory to be on all the time? Like a third party car alarm, gps tracker and dashcam running the continous draw from the battery?

[@classiccarmaintenance]

In that case you need to hook up these accessories to an external power source to power them before disconnecting the battery. We like to use a car battery charger that has a supply mode like this one amzn.to/3wxSJRg. Always first check your car accessories’ owners manual for instructions. However, it’s important to know that if you use an external power source, you won’t be able to tell if the parasitic draw comes from any of these hooked up accessories.

[@marifkhan2003]

How we can bring hybrid car in accessories mode without connecting negative battery cable? Or is there a different method to test amps drop in hybrid cars?

[@classiccarmaintenance]

Thank you for your question! For hybrid cars, due to the complexity of their electrical systems, it's best to consult a professional licensed mechanic who is trained on your specific brand and model. They have the specialized knowledge and tools to safely and accurately diagnose and address any issues, without causing damage.

[@jasonsherlock7480]

how did you have juice to your radio in the accessory position when your battery was disconnected!?

[@classiccarmaintenance]

When you hook up the multimeter between the negative battery terminal and the black battery cable, it functions as a bridge allowing power through. This, however, is limited by your multimeters' internal fuse(s). If you turn on too much electrical stuff and draw too much power, its fuse(s) will blow and you'll have to replace them.

[@stevet603]

I have a reading 0f 4.8mA (no matter what the setting on the multimeter the decimal point doesn't move?doing this) .I can't turn the ignition to accessory position to test the a draw increase as not even the dash or interior lights come on with the battery cable off, let alone the radio?

[@classiccarmaintenance]

There is no need to turn your key to the accessory position to test for parasitic draw. You should test this with all electronic components and accessories turned off and wait until the computer goes into sleep mode if you have a modern car. In our video we turned the key to accessory mode with the radio on to simulate a parasitic draw for demonstrational purposes, as our car did not have electric issues.

[@stevet603]

@@classiccarmaintenance Hi, new starter motor fitted. Today I tried removing all fuses one at a time with the multimeter in series on the neg cable. With car shut and locked, (apart from bonnet). After a while I got a 0.35A to 0.15A draw. Removing fuses one at a time (from all 3 fuse boxes), didn't do anything. Removing the positive feed to the alternator (from the battery terminal) didn't do anything, (did this checking for a shorted Diode causing drawback). The only way it totally disappeared was by removing the Positive connection to the engine bay fuse box; But that just made it read as zero. I don't know what else I can check now?

[@classiccarmaintenance]

Hi, could you specify if you disconnected the positive cable to the fuse box at the battery terminal or at the fuse box?

[@oncallguy]

thank you

[@classiccarmaintenance]

Glad you liked it!

[@erichernandez9751]

Hi, I have a toyota corolla 2017 manual transmission. It draws 140mA with the alarm activated all doors and lights closed. It is the dome fuse that draws 60mA out of the 140mA. It the turns to 10mA when a relay clicks after 20 mins. Is this normal? I hope I get noticed..

[@classiccarmaintenance]

You're good, that's perfectly normal for modern vehicles. The parasitic draw of 140 milliamps you measured in the beginning is because the dome light was still on and because the computer was still running in the background. Once the dome light goes out and the electronics go to sleep (the relay that clicks) you have a draw of 10 milliamps which is well below the acceptable 50 milliamps. That's why we said in the video that with modern cars you might have to wait half an hour or longer to perform this test as the cars' computer needs to go to sleep first.

[@erichernandez9751]

@classiccarmaintenance Thank you so much, that really eased my mind. You are very helpful! I hope you get tenfolds of followers and subscribers!

[@classiccarmaintenance]

Thank you for the kind words, appreciate the support!

[@kameronselvey4723]

So would I need to replace the fuse?

[@classiccarmaintenance]

No, the fuse itself isn’t the problem. Pulling the fuses is just a way to easily locate on which circuit the parasitic draw is located. If you pull the fuse that protects the radio only, for example, and the parasitic draw disappears, you know the radio or its wiring is causing a parasitic draw. The radio might not be switched off, as shown in our simulation, or there might be a damaged wire, or the radio itself might be faulty. Once you’ve determined by elimination which part(s) is(are) causing a parasitic draw, you know what needs to be repaired or replaced.

[@kameronselvey4723]

@ makes sense. So I know it’s my 12v plug. If I leave my stuff plugged it my car dies in about an hour and a half. Not fully just not enough to start. This just started happening recently so would the whole 12v unit need replaced somehow?

[@classiccarmaintenance]

When you leave electronics plugged into your cars' 12V plug, and it’s wired to be “hot at all times”, these electronics will draw power from your cars' battery and drain it even with your contact turned off, which is normal. If your car battery doesn’t drain when nothing is plugged in to your 12V plug, then there’s nothing wrong with your 12V plug. However, if unplugging the electronics from your cars' 12V plug does not fix the issue, you might need to repair or replace the 12V unit or sort its wiring.

[@KaylaHealy-f4e]

Hello I'm trying to setup my multimeter to the correct setting.on my multi meter mine doesn't have the A-~ but it has the 10A-~will that still work ?

[@classiccarmaintenance]

Hi! Yes this should work just fine if your multimeter can measure milliamps in that setting. Put it on 10 amps if this is your multimeters' highest setting and see what it reads. To get a more accurate reading, if your multimeter has multiple amps settings, then select the amps setting just above the parasitic draw your multimeter is reading.

[@KaylaHealy-f4e]

Thank you also when I plug the red leed into the 10A hole it doesnt get any readings. The voltage frequency hole(max 300v) gets readings with the red lead will that still work the same ?

[@classiccarmaintenance]

No, you need to measure amps, not voltage. Sounds like your multimeter isn't sensitive enough to measure the parasitic draw or is malfunctioning. Even if your car doesn't have a parasitic draw, your multimeter should measure some milliamps, never a zero value.

[@KaylaHealy-f4e]

Hello I bought a new multimeter with the correct settings . It.shows a 1.39 draw on the multimeter and right away the horn started going off . Am I doing something wrong ?

[@classiccarmaintenance]

It's impossible to tell what's exactly going on not knowing the setup of your specific car, but chances are you set off your car alarm by disconnecting your car battery. This could in turn activate your car horn. This would also explain the 1.39 (amps?) draw your multimeter is reading.

[@ChrisDonoho]

When I remove the negative power cable from the battery no power is going to the vehicle. Therefore I have no draw, even when I try to. The radio will not come on if the battery is disconnected. How did you get the radio to come on when the battery was disconnected?

[@classiccarmaintenance]

When you hook up the multimeter between the negative battery terminal and the black battery cable, it functions as a bridge allowing power through. This, however, is limited by your multimeters' internal fuse(s). If you turn on too much electrical stuff and draw too much power, its fuse(s) will blow and you'll have to replace them.

[@danschenck9442]

are you puttingignition key to on position

[@classiccarmaintenance]

To test for parasitic draw you need to turn the key to the off-position and make sure nothing is drawing power. In our video however, because we did not have an actual parasitic draw, we simulated a parasitic draw by turning the key to the accessory position. This turns on the radio which draws power, and shows up on our multimeter as a parasitic draw.

[@AaronFlynn-s8z]

How is your radio on if you have negative disconnected?

[@classiccarmaintenance]

When you hook up the multimeter between the negative battery terminal and the black battery cable, it functions as a bridge allowing power through. This, however, is limited by your multimeters' internal fuse(s). If you turn on too much electrical stuff and draw too much power, its fuse(s) will blow and you'll have to replace them.

[@patrinogwaro913]

And how does the radio draw power with the terminal disconnected ? Did I miss something ?

[@classiccarmaintenance]

When you hook up the multimeter between the negative battery terminal and the black battery cable, it functions as a bridge allowing power through. This, however, is limited by your multimeters' internal fuse(s). If you turn on too much electrical stuff and draw too much power, its fuse(s) will blow and you'll have to replace them.

[@utahenduro4808]

How did the radio turn on when the battery wasn't connected?

[@classiccarmaintenance]

When you hook up the multimeter between the negative battery terminal and the black battery cable, it functions as a bridge allowing power through. This, however, is limited by your multimeters' internal fuse(s). If you turn on too much electrical stuff and draw too much power, its fuse(s) will blow and you'll have to replace them.

[@IsaiahChapter53isAboutJesus]

Does this have to done on amps? Could it be done on DC Volts?

[@classiccarmaintenance]

No, it has to be done with a multimeter in the amps setting.

[@IsaiahChapter53isAboutJesus]

@classiccarmaintenance Is it too difficult to explain why? I'm trying to learn electrical and I know it can be difficult.

[@classiccarmaintenance]

In our video we're demonstrating the simplest way to test for a parasitic draw, with an amp draw test using a simple multimeter. Of course you could test for parasitic draw using volts by performing a different test, but you would need a very accurate professional multimeter to measure voltage drop across fuses and compare the measured values to a fuse voltage drop chart. This however is much more involved and time consuming as a difference of even 0.1 milivolt (which is 1/10,000th of a volt) can mean the difference between having a parasitic draw or not. That's why it's much easier to perform a parasitic draw test by measuring in miliamps, just like we demonstrate in our video.

[@MrHavokman]

If I disconnect the negative cable the car then has no power. How do I do the simulated radio test wtihout power?

[@classiccarmaintenance]

When you hook up the multimeter between the negative battery terminal and the black battery cable, it functions as a bridge allowing power through. This, however, is limited by your multimeters' internal fuse(s). If you turn on too much electrical stuff and draw too much power, its fuse(s) will blow and you'll have to replace them.

[@zeeshawnali4078]

In one shot you have the negative lead from the multimeter on the battery terminal and another you have the positive, does it matter which way you do it?

[@classiccarmaintenance]

No this does not make a difference. It will only change the "direction" electricity flows through the multimeter, displaying the parasitic draw as a positive or negative number. It does not change the measured value itself. If you connect the multimeter between the negative battery terminal and the battery cable with the black test lead on the battery terminal, it will display the parasitic draw as a positive number. Put the red test lead on the negative battery terminal and the black test lead on the battery cable and it will show the exact same parasitic draw, but as a negative number with a "-" sign in front of it.

[@zeeshawnali4078]

@@classiccarmaintenance thanks!

[@theycallmegeeg]

Once you find the parasitic draw, do you change the fuse?

[@classiccarmaintenance]

No, the fuse itself isn’t the problem. Pulling the fuses is just a way to easily locate on which circuit the parasitic draw is located. If you pull the fuse that protects the radio only, for example, and the parasitic draw disappears, you know the radio or its wiring is causing a parasitic draw. The radio might not be switched off, as shown in our simulation, or there might be a damaged wire, or the radio itself might be faulty. Once you’ve determined by elimination which part(s) is(are) causing a parasitic draw, you know what needs to be repaired or replaced.

[@TheChunckymunkey]

Would you just replace the fuse or would be something more complex?

[@classiccarmaintenance]

No, the fuse itself isn’t the problem. Pulling the fuses is just a way to easily locate on which circuit the parasitic draw is located. If you pull the fuse that protects the radio only, for example, and the parasitic draw disappears, you know the radio or its wiring is causing a parasitic draw. The radio might not be switched off, as shown in our simulation, or there might be a damaged wire, or the radio itself might be faulty. Once you’ve determined by elimination which part(s) is(are) causing a parasitic draw, you know what needs to be repaired or replaced.

[@TheChunckymunkey]

@@classiccarmaintenance oh, in other words there’s something wrong with car that’s going to cost a lot of money to fix. Got it. Currently having the issue with my battery dying after only sitting for a week with driving.

[@classiccarmaintenance]

Not necessarily, no. It might be as simple as a loose wire, the interior, trunk or glovebox light that stays on without you noticing. If you can pinpoint where the parasitic draw is located, you can either try to fix it yourself or tell a professional where it is located, saving him time and saving you money. About your battery dying after a week, you said it was while daily driving it? If that’s the case then you might have a bad alternator. Your car uses electricity from your battery to run and operate all the electronics, and your alternator is powered by the running engine to charge the battery while driving. If your alternator doesn’t work properly the battery won’t charge and will drain even when you drive your car. We have a video on how to test your alternator with a multimeter as well so you may want to check it out, it’s a really simple test.

[@TheChunckymunkey]

@@classiccarmaintenance mistake on my end, it’s not a daily driver. I have a company truck. My personal is driven 1-3 times a week sometimes less.

[@classiccarmaintenance]

Our advice is to first test if the battery is still good with a battery tester, then check if the alternator still works. If both battery and alternator are OK, you want to look for a parasitic draw. We have a video on each of these subjects, so make sure to check them out, it’s easier than you might think.

[@gegervary]

How does the radio in the car turns on if the negative lead is off? 🤔

[@classiccarmaintenance]

With the multimeter forming a bridge between the negative battery terminal and the negative battery lead, there is enough current passing through the multimeters' test leads to power the radio and other small accessories. However, the amperage is limited by the capacity of the multimeter itself and its internal fuse(s).

[@DetailDuck]

If I hook my multimeter up like you did, should I still be getting power to the car?

[@classiccarmaintenance]

Yes, the power will run through the multimeter but will be limited by the fuses inside your specific multimeter. If the power demand surpasses the capacity of the fuse(s) in your multimeter, the fuse(s) will blow. For example, this can happen if you try to start your car.

[@drraspberry]

I cannot thank you enough 🙏🏻🙏🏻🙏🏻

[@classiccarmaintenance]

Glad you liked it!

[@CryTwink]

I love Jack

[@citymarine7256]

How does the radio turn on when the battery is disconnected?

[@classiccarmaintenance]

With the multimeter forming a bridge between the negative battery terminal and the negative battery lead, there is enough current passing through the multimeters' test leads to power the radio and other small accessories. However, the amperage is limited by the capacity of the multimeter itself and its internal fuse(s).

[@Autofixgarage-ng]

Hope removing fuse & replacing method won't give wrong readings in a case where a removed fuse controlling a particular component will make d certain modules go to sleep.

[@classiccarmaintenance]

That's why with modern cars you have to wait half an hour or sometimes even longer for the computer and electronics to go into sleep mode before performing this test.

[@itzzlarry1338]

Does this work for ATV's?

[@classiccarmaintenance]

Yes, this works for any vehicle with a battery and fuses.

[@matsudakodo]

I'm connected as shown with a Southwire 21550T but current isn't passing through. Stumped.

[@classiccarmaintenance]

If you can’t detect anything even after verifying that your multimeters’ test leads are properly connected and making good contact, the dial is switched to ⎓ DC Amps (with the dotted line under the straight line) and the DC Amps setting is switched to a range that can detect milliamps, then there might be a blown fuse inside your multimeter. You can easily screw open your multimeter and take out the fuses one by one (if there are multiple) to test them for continuity. If you can’t detect any continuity then the fuse is blown and you’ll need to replace it. If the fuses are ok, then your multimeter might be malfunctioning.

[@matsudakodo]

@@classiccarmaintenance thanks, I will look into that. But I'm also thinking this meter can do DC current through the clamp only. Sounds odd, but even the manual says to use the clamp for DC current.

[@66gosser]

Just to confirm, you mentioned that the battery needs to have a full charge in order to test for parasitic draw. My battery is only reading 10.7v, and my amp meter isn't picking up any draw whatsoever. Sound about right?

[@classiccarmaintenance]

It's a good sign that your multimeter isn't picking up any parasitic draw, but for an accurate reading you should always first charge your car battery fully before checking for parasitic draw.

[@shimanoo11]

Do you need to lock the car first?

[@classiccarmaintenance]

You don't need to lock the door. Just closing the door is fine, unless the parasitic draw is in the locking system, but that's highly unlikely.

[@shimanoo11]

@@classiccarmaintenance Thank you so much!

[@Artur-Itas]

INTERESTING SOMETHING HAS BEEN SEVERLY DRAINING THE POWER FROM MY CAR BATTERY LIKE A VAMPIRE IN THE DESERT. THE BATTERY CAN'T HOLD A CHARGE TO SAVE IT'S LIFE. HOPEFULLY THE MECHANIC CAN FIX IT, CAN'T WAIT TO FIND OUT THE CAUSE. IT IS SO ANNOYING.

[@tiffanyv4205]

Did you ever find out??

[@kbengson9163]

​@@tiffanyv4205Looks like the vampire draw got Artur-itas after it sucked the last bit of life out of his battery,the mechanic he took it to,and all the other techs in the garage. No one has seen or heard from them in months & months 😂

[@johnpilkington6879]

Another tip is fit a buzzer between the earth terminal then when you pull the suspect fuse the buzzer will go quiet instead of keep lookin up at the multimeter screen 😎

[@classiccarmaintenance]

This could work, however, the buzzer will only sound when it gets enough power. Depending on how small the parasitic draw is, the buzzer won’t sound at all or too faint to hear it. So, in our opinion, that’s too many unknowns.

[@bivideo7]

Read mV drop across fuses...

[@agde0968]

Thanks bear in mind minimal battery drain can give many months of”Thrustration” The culprit a very small car battery and an aftermarket hardwire to a Nextcam dashcam. The manufacturer may say it won’t cause issues , for me it’s cost £60 plus many hours of work and a non starter😿🤐🥵

[@damon-t4l]

Wouldn’t a draw of 2mili amps be too little?

[@classiccarmaintenance]

2 miliamps is great, the lower the number the better.

[@XpertHeadyVids]

You said to keep doors locked all time. But you opened the door to get in to the fuse box, wouldn’t that mess up the test?

[@classiccarmaintenance]

That’s a valid question, you have a good eye! If you have to keep your door open to film the testing process like we did, or because the fuse box can only be reached with the door open, you want to manually lock the door locking mechanism or tape off the door jamb light switch to prevent keeping the computer(s) awake and to shut off the interior light(s). If you manually lock the door locking mechanism with the door open, do not forget to unlock the locking mechanism before slamming the door shut though! It’s a good idea to put some tape on the door or on the door handle as a reminder. Because our ‘98 Wrangler only has a very basic ECU, it does not “lie awake” (pun intended) over an open passenger door. We just removed the only interior light bulb to prevent it drawing current.

[@XpertHeadyVids]

@@classiccarmaintenanceokay got it thank you! Great video btw!

[@camillecooper1964]

I wish I can fix my car for myself at times 😢

[@I.Live4oldcars.prospecting]

I did this test on my car. But I'm confused. Can you help please? My multimeter shows 0.066 . Sometimes goes upto 0.070 .

[@classiccarmaintenance]

Your measurement of 0.070 (70 milliamps) is above the accepted 0.050 (50 milliamps), which means you have a small parasitic draw. You now need to locate the fuse box and start pulling the fuses one by one to see on which fuse your parasitic draw is located, as shown in our video. Once you know on which fuse the parasitic draw is located, by further elimination you can now determine which wiring or electronics that are powered by this fuse is (are) causing the parasitic draw.