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.
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).
@@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 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.
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!
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!
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!
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.
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!
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 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, :))
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.
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.
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 😎
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.
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😿🤐🥵
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.
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.
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?
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.
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.
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.
@@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 😂
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.
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.
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?
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.
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.
@@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.
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?
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.
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?
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.
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?
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.
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.
Everytime you remove and install a fuse, it's possible to restart the networks. Then you have to wait for the networks to sleep. This can take 45 minutes on many cars for computers to sleep. This testing process is outdated and flawed for any car built after 1996. A low amp clamp and DVOM to run parellel with fuses is the way to go.
Thanks for your input! In case the parasitic draw increases after plugging the fuse back in, you know that some part of the cars' electronics have woken up, that's absolutely right in case of some modern cars. But the principle of locating the parasitic draw stays exactly the same. Just like initially, you only look at the amp drop when removing the next fuse, yet with the new amperage reading as the benchmark. So if you pull the next fuse and the amp draw drops significantly, you know this circuit has a parasitic draw somewhere, regardless of some electronics that may have woken up by reinstalling the previous fuse.
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.
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).
After 6 months of flat batteries , my draw was minimal most videos say it can be ignored, not for me very small car battery aftermarket hardwire. Of Nextcam dashcamwas the culprit Beware!!!😿🥵🤐
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).
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.
@@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.
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.
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.
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?
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.
@@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?
You’re absolutely right, disconnecting the car battery is not an issue with old school cars that don’t have advanced electronics or accessories. However, If you have a modern car with electronics and/or accessories that need continuous power supply to not lose data and settings, you need to hook them up 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.
@@classiccarmaintenance Lately with my "modern car" ('07 Acura MDX) I had a parasitic draw (well-known to dealers and many, many owners) and I became an armchair RU-vid "expert" on the issues of draw and memory saving. With the investment of a $40 Digital Clamp Meter (that also has other Multimeter functions and probes) here's what seems to be the best "modern" approach IMHO (mostly from a former Acura mechanic): 1) Put the clamp meter around the ground cable to measure DC amps. No battery cable disconnection. No outside power e.g. 9V battery, another 12v battery, or jump starter, needed to maintain memory components or to hide a parasitic draw. 2) Test compatible fuses (conductive access to both poles) with a multimeter in a systematic manner without pulling the fuses to test voltage drop. If a wiring diagram is available that's even better, or just common sense from labels on the fuse box works, e.g. if the radio or wipers work - don't bother testing their fuses.
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.
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 ?
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.
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 ?
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.
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.
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.
If you make sure that everything in your car is switched off before testing and if the parasitic draw is below 5A, it will work just fine. Worst case, if the parasitic draw is higher than 5A, your multimeter might blow its internal fuse. Most multimeters have glass fuses, which are cheap and easy to replace, so that’s no big deal. We’ll be making a video and a post about that in the near future, by the way. If you don’t feel confident about your multimeter, you might want to check out our post about the best multimeters through the link in the description. A good one doesn’t have to be expensive. Hope that helps you out. Happy cruisin’!
