I love Matt's methodical and scientific approach. One minor point: Matt describes the Snap On low-amp clamp as "inductive". It actually uses a Hall Effect sensor to read magnetic field, not an inductor (transformer). The inductive approach only detects varying current flows, so is widely used in current clamps only intended for measuring AC current in mains wiring. For automotive you need to measure DC (steady) current which produces a steady magnetic field. The Hall Effect sensor can detect either. Obviously when buying a current clamp for automotive use, make sure it says it's for DC in addition to AC. Also, these sensors and associated clamp parts only have a limited sensitivity range, so those suitable for very high currents don't give you much precision for small currents. That's why a big deal is made of "low-amp clamps". Again choose according to your application -- you can usually find a PDF of the manual online to check the specs.

I didn't know about that voltage drop method. I will definitely be using that method from now on. I love it when people come up with ways to make our lives easier.

When I see vehicles go to sleep, I expect a 40-50 mAh draw. a good car can be much less. Good video and explanation.

I always set the DMM plugs back to 'volt/ohm/etc.' mode DIRECTLY after using it in amp mode. Never leave it in amp mode. It can be 'exciting' and expensive,if you forget. Also,check the probe connections each time before you use it. Just be mindful,and it's not a problem. The 'use the fuse as a current shunt' method is generally good -IF the circuit is drawing a fair amount of current,AND your DMM is sensitive enough to read it. Low current draws will only present a minimal voltage drop across the fuse..your DMM may lose it in the 'noise floor'. If you had,say,~100ma draw,across a 30A fuse,you might only be looking for a reading of a couple mV. It's a good,quick,test,but just be aware of it's/your equipment's limitations.

Thanks for the warning about checking for voltage with a meter while set up on current!

Awesome vid. Very useful information.

the great thing about this method is that i have ruptured fuses before just from pulling them. i don't know how often it happens but the filaments are connected to the terminals and they are quite flimsy. another great thing about it is that some cars use the same fusebox for multiple models and therefore there are some slots not in use, so if you are going to go pulling them out, be sure to take a picture of it with your smart phone first so you dont put them back in the wrong place! your method totally bypasses all of that.

Why does he sounds like every auto teacher I ever had? Very informative, cheers!

excellent videos as I'm taking electrical course at UTI. big help

exellent video,have had lights on in glove box,in boot,or stereo not go to sleep,still on,key out,i made up 2 dead fuses,blown,micro and normal blade fuse,size,solder a wire to each side,grind off a bit plastic ,and now got a test plug,pull suspect fuse out,plug in your special fuse with 2 wires,conect test meter for test,found not get pin slip and fast way to test,very cheap to make ,use blown fuses,any colour,amp,works well,keep up the good work,your educating the world,earn good karma

thank you so much for your video's I'm slowly becoming a mechanic. Your video's helped me diagnose my wife's car and now it works

Excellent video. I cant stress enough how important it is to keep a "light touch" when diagnosing sleeping current. Disturbing ANY power when diagnosing may cost you an opportunity to fix it right the first time. Most of the draws that I have experienced are caused by intermittent bus activity. One module will wake up and disturb everybody else on the bus. If your lucky the draw is permanent and consistently the same amperage.

Bought my Camaro Z28 over 10 years ago here in Australia from a guy in Canberra when I went to pick up the car he had installed a brand new Federal Battery. He said he had tryed to charge the old one but it would keep failing to start the car after a few days. Long story short my son 8 year old found the problem. As I drove the car into the garage which was dark he asked me why the glove box compartment was lit up ?. Because he was lower in the seat and the gaps in the inbuilt GM loose fitting lid alowed him to see this. I adjusted the poorly made mechanism and fixed the drainage issue then on to all the other problems. Thanks Matt big follower in Australia Graeme

dam that voltage drop test one the fuse is sharp .nice tip thanks matt

Nice twist on parasitic draw testing, thanks for sharing the info.

Under some of these dashes laying on your neck, would be a challenge working with two probes, like Explorers and other bitches. I bit easier pulling fuses with the right tool for me. I'm 62 years old and have been doing nothing but this stuff all my life. Your well spoken, I'll bet many benefit from your great presentations. Thanks, buddy..

A 5 star video. --- as always :-). Aftermarket ice installations and ant-theft systems are always top of the list of suspects but if the parasitic draw is large my prime suspect is usually leakage back through the alternator diodes. I had read about the fuse voltage drop test before but never tried it would be worth experimenting to find just how small a current it can detect with a typical Chinese made DVOM A while back I bought my daughter a 1.4 litre car at auction, it turned out to have a 80mA parasitic drain that was enough to discharge the small battery in a few days. To track it down I did an eBay buy a bought couple of those ammeters that plug into blade fuse sockets (one for mini blade and other for standard blade sockets) turned out to be about 70mA was going through the security transponder reciever aerial round the ignition switch.

Great video as always. I have one Chevy Lumina with the same parasitic draw problem. Most part I already did as you explained in the great way and the rest I will do it tomorrow. Hope I would film it also for further reference. Regards,

Thanks for another great video!!! Please keep up the good work. One think I like to do to save some time is check all the fuses with a test light first! You of course check them with the key off. That way you know what fuses are actually hot with the key off and will save some by not time testing all the fuses when actually only 2 or 3 may be hot with the key off.

Pulling fuses one at a time is great for older cars; not for newer cars. They have so many interlinked and overlapping systems that something as seemingly harmless as pulling a fuse can set into motion all sorts of electrical activity that can literally take hours to completely cease. The superior way to test is by leaving the fuse in place and test each circuit via the test points on top of each fuse. Performing the in-series battery test first is a great way to see if there's a loss, but this is a much better second step than pulling fuses, unless you have an older car. DEFINITELY don't start yanking fuses on vehicles like late-model Mercedes, ha ha.

What an excellent educational channel! You filled a void on Meyer settings specifically where they must be as you did you old school new school comparison (and thanks to your follower that tipped you about the new school alternate method. Thank you also! I'd better check if he has a channel so I can subscribe). Thanks for the info to both of you! I have a parasitic draw on my 2001 C240 mercedes sedan and it's truly in stealth mode. I think I may have hope in finding it thanks to both of you and You Tube's algorithm that brought me to your channel. Keep up the excellent work and ill let you and your subscribers know about my progress with my old but excellent running Benz.

Awesome Matt. Great video

excellent, I looked at many videos just to find out the adc mode. You are the best, others are there just to give out fake knowledge . Thank you, sir, you're the best.

If ur going in series with the battery u might be able to loosen,wiggle the terminal up and connect on the bottom of post,great vid thx

Thanks for sharing, sounds like a good idea.

Parasitic draw testing Voltage drop is One of my favorites

Great info - thanks !

Every bravada I come across is a nightmare full of problems. last one I worked on was stuck in 4wd, battery died every night. needed the intake manifold gaskets changed. The blend door was stuck trying to calibrate itself so it would switch between hot and cold air. and many more problems. After finding your videos I've learned many little tricks. You put out the most informational automotive diy videos I've found on youtube.

THAT is a great example. I always drop the fuses anymore. Then the challenge comes, WHY is there a drop. Great video, just found your site.

Been having issues with my 2007 Trailblazer, the battery would drain after 2-3 days idle. found that the OnStar was pulling .4A when the car was "asleep" and I don't even use this service or feature. Awesome way to check for a parasitic draw without disconnecting the entire battery. Thanks!

Can you recommend a decent current clamp meter for automotive use in checking for parasitic current draw? Thanks - Jim

Good stuff man.

Great Video! Well explained! liked ! Subbed !

Can you post a link for an inductive amp probe that I can use with my multimeter? Every time I search for one all I find is stand alone multimeters with an integrated clamp. My multimeter is an Agilent (Keysight) u1231a in case that matters. Also, do you have a recommendation for an entry level oscilloscope?

hello, when you did the direct amperage test were the headlights still on or did you turn them off?

I had a parasitic draw then I found out it was my wife.

The AMP clamp with Voltage Drop test is a better approach. Voltage drop testing is quick and easy way to detect problems, thanks for your efforts Matt.

Both radio power supply circuits are wired to continuous hot rather than radio KAM to hot and the radio power to the ignition switch.

I don't think you should be afraid of using the amp range of your DMM. Just remember never every leave the probes in the amps jacks after using. Always switch back to the volt input. More expensive DMM's will beep when you are in the amps jack and switch to ohms or volts on the dial.

hi, same method can be applied on 24V right? after testing voltage drop, will it be safe to amp test the fuse socket on 24V? thanks

keep an open mind, never stop growing💯

Great info, very appreciated.

A DC amp clamp can be used with MIN/MAX, with APO disabled, to detect intermittent parasitic draw.

Haha! Megan Traynor is the owner of that vehicle. Dayum! I love my bass, but who the hell listens to music w/bass all the way up and treble all the way down?!?! That sounds like shit 100% of the time!!! Thanks for creating a channel to share all the knowledge that you have w/us, and whats still to come. I just subscribed yesterday, and know a lot more right now than i did before i woke up yesterday morning. Aloha.

I have 2 Chevy premium factory stereos in my garage that both worked fine but would drain the battery in 3-4 days. I used the old school 12v test light in series on the battery neg terminal to narrow the problem by pulling fuses util the light went off, then narrowed it down from there. BUT I had to pull ALL the fuses at once because pulling and replacing one at a time would not cut the light. I finally found the 2 fuses that somehow BOTH fed the radio circuit. Spent hours investigating for wires crossed or spliced and all appeared factory correct and could not duplicate the draw with the stereo disconnected. Hot wired the stereo direct to the battery and 1.5 amp draw (turned off). Got a used $10 stereo from a junkyard and hot wired before installing, 1.7 amp draw. Gave up and left the fuses out. 1998 Chevy Suburban. This car is only used around the ranch anyway so no big deal. I'm 68 but I keep learning!

Great video as always. thanks Matt

For usefulness at this task, be careful which Ammeter you pick up. After watching this video at 6:19 I picked up a Fluke 115 multimeter and Fluke i410 Ammeter. What I can tell you is that this Ammeter is only accurate to .5 amps. To ensure I did not have a parasitic drain I had to connect the multimeter in series to the negative battery terminal and cable. With all electrical draws off, the Ammeter showed I had a .5 amp draw and the Multimeter showed I had a .0075 amp draw. This particular Ammeter is not precise enough for parasitic draw tests on a car battery but it is great for Alternator amperage output and starter amperage input tests.

Great video and thank you for it! When you were checking voltage drop on the fuses what millivolt setting were you on 200 or 2000?

Outstanding video!

Sir I totally understand what you mean about being brain dead and want people to learn, I love learning but honestly I just don’t have time to learn electrical, but I will be signing up to your other channel, if I can learn stuff for the price of a cup of coffee that’s a good deal, thank you.

I prefer to put one probe on B+ (At the battery) and I will use an extension if necessary and use my second probe for probing fuses. Since voltage drop tests are NOT polarity sensitive, this prevents me from putting both probes in tight areas under a dash. You only need to check one side of the fuse to confirm current flow, if you use my method of going to the battery.

what is the scope you're using? the one with the big screen .

First video of yours I wasn't too impressed but this one you nailed it. With doors open and latched with dome buttons depressed to start diag testing. Mercedes Benz many years back had the voltage drop across the fuse and they had a formula on different fuses using Ohms law to get the actual current. Overkill as I agree with you when you see the mv on the dvom you know somethings wrong. Then out comes the amp clamp like you use to verify. These days waiting for cars to go to sleep is a big pain or you chase your tail till can shut down or other components. Great video, now I can subscribe.

Great video overall but instead of using your multimeter and looking back-and-forth at the numbers for the drop better to use an amp hound, you can do a quicker test across the fuses and a different tone will let you know when there's current going through & u found yout draw. It will even let you know the voltage that's being drawn on the circuit you're testing.

very educative. Thank you regards

What is the name brand of those meters he's using?

One safe way to figure out the current going through a fuse is to pull the fuse and measure it's resistance (after measuring the voltage going through the fuse.). Volts divided by resistance will give you current. Another trick I use to protect my meter when doing amp tests, is use a jumper with an inline sparkless or electronic fuse with a lower rating than my meter. These are not the thermo breakers found in most auto part stores but fast acting brakers, sometimes used used in race cars. The advantage of these brakers is there no sparks when wires short and of course current is restored when the short is cleared. I also use this jumper for doing electrical jumps because the sparkless circuit breaker increases the safety of these operations. (Gasoline and sparks is not a good combination at times.) Yeah don't always do this since I have blown a few meters. Don't despair it's just a fast blowing fuse in the meter. Some are a pain to get at. However don't use an automotive fuse. What is needed is a fast blow fuse use in electronic devices. Radio Shack was my source, but alas, check on line now. They are cheap, just a pain to replace and get.

SUBSTANTIAL Schrodingers Box Amazing tutorial great thank you very much helpful video. Take care and have a great Easter 🐣 From Nick Ayivor from London England UK 🇬🇧

Thank you

I use the fuze voltage drop test but don't remove the fuse to measure the amperage draw. There's plenty of fuze voltage drop charts for various fuzes that correlate the amperage to voltage drop . Good testing 👍

Whoa! Voltage drop across a fuse. Sweet.

Where do you get the add multiply the voltage by 10 formula to gget the amp reading from?

I like the voltage drop method. All ready have a DC Clamp meter, initially used for addition of solar panels and habitation requirements. I have used TPM total preventative maintenance in a work environment. I would like to use my scan tools Multiecuscan AlfaOBD and obdlink (laptop and android live in van all time) to routinenly bench mark the engine. Its a 2.3l turbo diesel (euro6 Ducato Dodge Ram ie EGR and DPF) Have you any idea as to sensible PIDs to monitor. (the Marelli ECU does not monitor fuel trims) Have you any vids on this application, searching for something that is not there yet. Sorry if some of the terminology is different

Fantastic thanks

Very good!

Great video, Great deal of knowledge perhaps. I was huge fan of scannerdanner, but you are not less than him .

How do i narrow it down when i know the circuit at fault? MY problem is with the fuse that feeds the dash and many internal things. Do i have to start pulling the dash apart??

Nice to see you upgraded to a better camera.

This works, however, the real nightmare are intermittent current draws, such as a rear windshield wiper trying to return to position. Noting also some older vehicle security systems (such as my 91 Jeep) have a fairly large constant current draw that needs to be allowed for when doing the testing.

Great video thank you for sharing

Good stuff 😮

What amp meter are you using or which one would you recommend thank you great video

Great video. Old TV tech. I heard a lot of good advice. You are probably one if not the most accurate tech that is sharing info. People are welcome to double check.. V=IR. Amps or I is V/R..using the above relationship. I suspect a fuse has infinite resitance when blown. So 12/infinity.. is .000000..etc. So no current. Say, I found a voltage of 12 volts the across a wire fuse. V=IR; 12 = I x infinity... there is no current..so can 12 = O x infinity.. be true. No..there will be.no voltage drop across the fuse itself..There would most likely be voltage of some kind to ground. .Voltage is basically potential .. The math will work.. It's really a mute subject. There are charts that give the voltage over the fuses. I have never used this method. I would suspect a printout from a diagnostic machine would be helpful. Remember, it is the voltage across the fuse that is important. As the current starts to flow..I've read that filiment of the fuse increases in resistance. Ive also read some charts that are comparative ..the larger amperage fuses change the milivolts that are typical across the fuses. That is fascinating study. Of course the obvious here is be careful..at all times.

My 2002 Jeep Grand Cherokee 4.7L-V8 has a 4A draw from the door harness wiring. If you have a 99-07 Jeep Grand Cherokee, I encourage you to check the wires in the rubber boot in door by hinges. It's an extreamly common issue with WJ's.

:) thank you (from the cheap seats, *waves*)

my 97 Jeep Grand Cherokee had a parasitic battery drain that was tracked to the huge 50 amp fuse then to the #7 fuse inside at the lower passenger side fuse panel. So many possible drains, shorts or shorts were possible that it was easier to just jump the 50 amp fuse with an inside toggle switch with indicator light. Ended the problem. Has the entire full width instrument panel out once and did not feel like doing that again. Cigarette lighter and USB port are eliminated separately.

Hey, Matt. You have covered using a multi meter in great detail as well as showing your subscribers how not to fry them. Have you considered making a video to show how to replace those two fuses inside your multi meter? Show what fuses they are and how to replace them/where to buy them? While you are at it you could show a list of functions of a multi meter and maybe include a few different models and maybe include a bonus section of the patterns of OBD II codes (what a P code is, what a B, C or Unidentified code is, how to tell if it is manufacturer specific or generic) What years qualify as (typically) an OBD I or an OBD II and the basics of how to read a code reader in general. Reasons this would be helpful: I am more familiar with using fluke multi meters so for more experienced subscribers this would be more knowledge in the bank about different brands of multi meters, and how to properly maintain them if (and when) you make a mistake. We all know it happens Secondly: My grandfather is not a mechanic and I have gone over this several times with him. Both the multi meter bit and the OBD II reader and how to properly identify a code without the reader telling you. He is one of those "carburetor master race" people that thinks it is pointless to learn how these things work even though he drives a 2011 Dodge. I am not a good teacher and he doesn't listen to my advice. I know he will keep this truck for decades past the warranty and eventually it will have problems that I may not be there to fix for him. Maybe he would listen to you better seeing as you are a bit closer to his age.

Thank You! 🙏

I agree wholeheartedly with the basic reason to avoid putting the multimeter (who calls it a DVOM anyway?) in series with the battery in the first place. However, does your meter make a loud sound if you have leads plugged into the 10A jack but switch to a voltage setting? Nicer meters do this, and it reduces the risk somewhat. Make it a rule to touch probes only once the meter is configured, and there's some safety there. Nonetheless, avoiding that configuration entirely is a good plan. Love the channel.

Hello. Fairly new to your channel and recently subscribed. I'm just a DIY'er and have a question. I don't want to hook up the DVOM in series with the battery and take a chance of messing up the PCM. Can you just skip that part and start measuring voltage at each fuse and when you find one with voltage present change over to 10 amp current? Kind of like you did in the interior fuse box. Thanks.

so one thing is unclear...you have the black cable hooked to the parasitic device around the negative cable. I am assuming the red doesn't go anywhere ? It seems odd that there is no closed circuit...can you expand please?

hi excellent video - thanks.. if it's a circuit that I need when the car is running, can I just wire a "circuit kill" 12v 10A switch in series inside the car on the negative side of the fuse for the circuit that has the draw and turn the switch off when I park the car?

Excellent !

what scope is that?

I have an '02 excursion. It reads 68 with battery - disconnected. When I turn ON the head lights/parking it drops to 48-49. When I unplug the switch it stays at 68. So would that be something to do with the headlights?

i found the drain cause ,it was multifubction module, i changed it but still multimeter give 2.5 , what can i do to solve it?

I ground my test light and go from fuse to fuse to which one is live and then go to the multimeter

Matt, I have a 2007 SRX 3.6l consistently draining my new $200 AC Delco OE replacement battery. Has no DTC’s. However, scan tool alt. Test suggests over charge is the cause of ncns condition (drained battery)? After trickle charge on battery starts right up. Draw test void for amp draw? What is your thoughts? Don’t want to “shoot the canon”? Charging around 14.6/14.7 at idle head lights low beam nothing else on. New OE Alt. $400!

In my opinion, the easiest way to determine the current draw is to measure the voltage drop across the fuse and refer to a chart for the current drain at static1.squarespace.com/static/582b77aa6a4963c3f199b0a5/t/5989d68bd2b857f1fa7fdc9d/1502205579335/Fuse_Voltage_Drop_Chart_-_Mini_Fuse.pdf .

great video thanks for the methods, now that you found the Parasitic Draw how did you fix the problem with the radio?

Great video and info, I'm learning lot's thanks. Is it true that with modern cars, with so many electronics, you can see considerable draw until everything goes to sleep, i recently did an amp draw test and saw over 2amps initially?

I have a 20amp DVOM but I was wondering about the clamp on amp meter you were using in the video where you clamp it around the wire without disconnecting the battery. I was looking at a few from electronic specialties but not sure any thoughts. Thanks and will probably signup to your other channel. Very clear to understand videos and am focused on schematic reading and understanding the circuits and component operation. Keep them coming

how about the fuse that powering up pcm always to keep memory, will it too going to show voltage drop on that fuse?

Hey Matt, guess what I just got done doing?? LOL....Yep... this video. Thanks as usual buddy!! You're the best!!

Another good video, Vdrop to narrow down the circuit, then amp check to confirm. good method. saves a lot of time messing with the fuses for sure. However i am curious to know, what on the radio was suckin juice when it was not supposed to be, and if it was hooked up wrong or whatever? =)

What brand and model of meter and clamp tester did you use in battery drain video..thanks

hi i got c270 cdi benz it cranks but not starts took it to a garage the guy said i need to get a new sam moulde which is too expensive pls help.

the fuse for the power seat and power windows keep getting hot and not working my 2006 ford taurus . what do you think is happening?

Cool technic with voltage drop, this is what we do on electronic, we put 1 Ohm resistor on the board, V=R*I if R=1 then V=I , but most of you already know that.

1:30 risky old procedure to spot excess amp draw involves disconnecting neg battery terminal set aside (this method forces you to reset your clock and radio presets). identifies a draw, then you pull fuses until you ID which circuit, first inside car, then under hood. 5:50 method two uses inductive amp probe 'dc inductive amp clamp' that you... 6:40 clamp around the battery cable without disconnecting it which measures (amps) magnetic field and outputs corresponding voltage signals to your dvom. you plug the clamp into yout DVOM multi like you're going to do a regular voltage test, set probe/clamp to 20A setting and loop it around neg cable. the DVOM is set to 20 VDC scale and we're reading volts (0.05v so you have to multiply x10 to get .5 amps). then you pull fuses until it drops to zero. 9:00 but it's still time-consuming when we pull fuses one by one. 9:43 method 3: we spot the fuse by detecting voltage drop between in/out side of fuse. 10:10 we will have minimal voltage drop so you will need a millivolt scale to detect it.