Improved Methods to Find Parasitic Draw (Battery Drains Overnight)

Here I show a couple of better methods to help identify the circuit responsible for draining a car battery over the usual "ammeter in series" technique- but while still using a basic DVOM.
Schrodinger's Box Quantum Mekanix site is here:
/ @schrodingersboxquantu...
My original video on parasitic amp draw is here (not in high def lol) :
• Diagnosing a car batte...
Understanding Voltage Drop video is here:
• Diagnosis and Understa...

[@Graham_Wideman]

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.

[@user-rw2tw8yl4l]

AC-DELCO Batttery, GM WARRANTY SCAMS; anyone else been scammed by them? they tout a no questions asked 3 yr warranty BUT when my new $375 battery failed in 2 weeks, i was initially DENIED warranty and now been waiting almost 2wks for replacement

[@777warhero]

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.

[@SchrodingersBox]

+argonian bilbo Thank the commenters for this one, especially Arlen Raasch. I would never have thought of this myself and in fact I would have bet a ton of money you cant measure voltage drop across a fuse with a basic DVOM.

[@777warhero]

Schrodingers Box Thank you Arlen!!

[@AGuysGarage]

+Schrodingers Box same, i would have thought it would have been in the micro v range. its just a small piece of metal after all. the face that there is a drop above the micro volt range baffles me. Because CSO says the resistance x the current = the voltage at a given spot. (Chuck Simmon Ohm)

[@DENicholsAutoBravado]

+argonian bilbo Agreed to thanking him. I remember getting the idea at the time he wrote it, but I haven't had a parasitic draw to chase down yet so I forgot all about it. With this video, the knowledge is locked in forever. :)

[@BernPisarcikJr]

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.

[@ralph1bart]

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

[@dntlss]

I did that recently twice in 2 days,26 dollars down the drain but much better than a 300 dollar meter down the drain, those Fluke fuses aren't cheap,lol, problem is we are so used to measuring voltage on batteries, alternators and things like that and very rarely we check for parasitic draws so its force of habit to forget to change it back and or put the probe back on its usual jack,part of being human.

[@graemer66]

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

[@SchrodingersBox]

Cool story!!

[@dangerdavefreestyle]

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.

[@PhattyMo]

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.

[@richardjohn5216]

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

[@WhenallthenamesIwantaretaken]

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

[@chrisroberson3344]

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.

[@james66872]

So true. If you miss the opportunity you’re going to be spending even more time

[@cmyk71]

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

[@jerrymont2595]

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.

[@mikeskilla]

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

[@Time4House]

hhahahhaha

[@Ty-kv3zb]

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.

[@schrodingersboxquantummeka2008]

+Tyler Buls Lol yes they definitely have been known for the issues you described. I think a lot of it has to do with using new unique technologies other cars at the time didn,t use (smart trac for example). I don't see a lot of Bravadas (only this one in fact) but I see tons and tons and tons of Vortec/4L60E's because they are so common in Denver.

[@DENicholsAutoBravado]

+Tyler Buls Where I've always ran into Olds Bravada is Google thinking that's what I meant to pull up when I was after autobravado, lol. I didn't even know it was a car, somehow I stayed oblivious to this SUV's existence.

[@joemarotta2237]

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..

[@ksauto1]

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.

[@joelburke331]

c Te 34wqq

[@ThecardoctorTV]

Awesome vid. Very useful information.

[@ozzstars_cars]

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

[@mechtechtools838]

+Ozzstar I agree, I'm a licensed automotive and heavy duty tech and I learned something new. Thanks

[@SchrodingersBox]

+buzzerauto Thanks guys- gotta give credit where it's due though- that viewer I mentioned is where I first learned this and to be honest, if someone told me you can measure voltage drop across a fuse I would say they were completely insane lol!!! Again the comments are often better than the material on this channel!!

[@TheNoBSZone]

+Schrodingers Box If you don't have an ammeter, you could always disconnect the battery cable and bridge the cable to the terminal with your tongue. First degree burn = small parasitic draw, second degree = medium sized etc.

[@SchrodingersBox]

+TheNoBSZone Aw man gross! But only because usually by the time I see a car there were 5 other people who saw it before me. That's a lot of backwash on those terminals!!!

[@PIANOSTYLE100]

@@TheNoBSZone We were told not to work on electronics with rings. Hmm. 30000 volts DC to ring.. conductor to Flesh acting as a ground. Very unpleasant. Maybe best to do what books say.

[@robertbeam8791]

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

[@SchrodingersBox]

+robert beam Lol, yeah I agree. Gotta hand it to the viewer who brought it to my attention though. Honestly I would have insisted it is impossible to see voltage drop on a fuse!!!

[@andrewwmacfadyen6958]

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.

[@oskarzepedarecords1824]

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.

[@PIANOSTYLE100]

Alot of that..Professionals don't like to give out everything..most had to learn the hard way...

[@numinous4789]

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.

[@SchrodingersBox]

AGreed- thus the purpose of this video. I too had to change my outdated methods as pulling fuses created too much variability. Testing the voltage drop across the fuse is really the best way IMO.

[@randyoehlert9571]

He didn't go there. Lol He's working on a 1991 model. Try that on a 2016 Lexus..

[@JahanZeb1976]

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,

[@SchrodingersBox]

+LearningZone Hey I haven't seen you for a while! Hope all is well my friend!

[@georgebonney90]

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

[@6980869]

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.

[@cpdahl83]

Great video as usual. I enjoy the humor too! BTW...that song is using bass as a euphemism for the "booty". Listen to the other words in the song and I think you will agree.

[@allhoursmaintenance3022]

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.

[@rrmech11]

Awesome Matt. Great video

[@johncantrell614]

Thanks for sharing, sounds like a good idea.

[@8953147]

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.

[@DENicholsAutoBravado]

+jake ounce Way easier, right?

[@8953147]

I I tested voltage drop on my headlight system and got a reading of .82 millivolts with no other problems in that circuit. With the car being 15 years old, the resistance within the wiring is starting to show

[@DENicholsAutoBravado]

jake ounce Yes, that does make sense. It's why as cars age I always end up adding ground wires to make things run better...I'll have to do a KZbin video on it eventually, right now I just have an article about it on my website; 8 gauge grounding wire upgrade - something like that.

[@DENicholsAutoBravado]

+jake ounce Did you see Steve Rob's comments how there are charts to see that voltage drop and know the AMPS based on that circuit?

[@AntonioClaudioMichael]

Parasitic draw testing Voltage drop is One of my favorites

[@carpenterfamily6198]

Great info - thanks !

[@ritzhandles7]

keep an open mind, never stop growing💯

[@carmo9693]

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.

[@SchrodingersBox]

sometimes it takes people a while lol.

[@DayClanTribe]

Here's a chart for that: www.powerprobetek.com/wp-content/uploads/2018/12/fuse-charts.pdf

[@Jonessxy]

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!

[@dcbigsky]

Great video as always. thanks Matt

[@advancednutritioninc908]

Great Video! Well explained! liked ! Subbed !

[@felixcat4346]

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.

[@kknows3512]

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!

[@SchrodingersBox]

Yes the testlight in-line is also a good technique. the only thing I don’t really like about it is if there is like 100mA of current it doesn’t show on the testlight but you still have a moderate draw.

[@esc2dos]

Great info, very appreciated.

[@bryans8193]

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?

[@SchrodingersBox]

You want it on the most sensitive setting your meter offers

[@Wildcat5181]

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

[@elomeli211]

Good stuff man.

[@jimmason7353]

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

[@alamzeb6342]

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

[@SchrodingersBox]

Well thanks man. I have come to be good friends with Paul and I can assure you, I cannot hold a candle to that guy! We have the same exact thought process and analytical approach, but his experience and depth of knowledge trumps mine tremendously!!!

[@alamzeb6342]

Thanks for reply. we should pay equal respect to both of you (Mr.Paul and you). You both are blessings for man kind. May you guys stay happy and healthy with us.

[@Thurge]

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?

[@danielbriese3972]

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.

[@danielbriese3972]

I've been drinking so I am sorry if that previous comment doesn't make much sense but totally do it that would be great thanks. =)

[@deanyaddow7056]

Daniel Briese nh

[@gadgetsense3981]

Nice to see you upgraded to a better camera.

[@SchrodingersBox]

You must have seen my original videos- those are from years ago before I found out this would catch on so quickly so I didn't invest in good equipment.

[@ClemAutoElectricalAuckland]

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

[@duramax78]

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.

[@lmtsmt847]

Same here now I'm trying to study it for ase

[@samspade8612]

Outstanding video!

[@SchrodingersBox]

Thank you very much!

[@code3responsevideos872]

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.

[@Graham_Wideman]

This method can be fooled though. If there's a current draw on some other circuit that happens to share the same positive rail (eg: downstream from some master fuse or relay) as the fuse you are testing, then you'll see a drop at the fuse you're testing even with no current flowing through that fuse.

[@arthurfricchione8119]

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

[@SchrodingersBox]

ANy DVOM with 10A DC will do.

[@404notfound.....]

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.

[@dbiberdorf]

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.

[@DENicholsAutoBravado]

+GeekPriest On one of his tips and tricks, he showed a rubber band over his DVOM that he puts over the control until it's off of the amps setting again. I had noticed he had abandoned the trick, and now, I know why.

[@seshachary5580]

very educative. Thank you regards

[@SchrodingersBox]

Glad you liked it!

[@nickayivor8432]

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 🇬🇧

[@SteveRobReviews]

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 👍

[@schrodingersboxquantummeka2008]

+Steve Rob Yes I was figuring there must be a correlation between the voltage drop and the amperage but I wasn't sure. Good to know- saves even more time.

[@SteveRobReviews]

+Schrodinger's Box Quantum Mekanix Matt here's one link to use in the future and share with your viewers info.powerprobe.com/fusechartsdownload

[@trainer2018]

+Schrodinger's Box Quantum Mekanix Matt also sometimes depending on how the circuit is made up if you disconnect the fuse say for example on a module and put your amp meter in line you will wake the module up and get a improper reading. So I would get a chart to go by in my opinion. I believe Toyota has one, Power Probe and Dan Sullivan has one in his Fet book. I have experienced this problem myself that's why I am telling you about it. Found the info on Identifix. So as Steve Rob said I wouldn't pull any fuses. Just use a chart. Also on your Snap On Low Amp Probe, what is the minimum amperage it will read? Good job on the video.

[@SteveRobReviews]

busjockey1 Mike I have many amp clamps and can't get a reliable reading in the ma range at all , my fluke will not read low amperage either. I've taken the fuse out and put a jumper in and can't get an amp clamp to match the dmm in series. I like to put a fused jumper in and read the voltage drop and do the conversion but you really need a meter that can read 1 ma . Oh yeah them $5 packs of 100 fuses don't work their a pile of junk, ha I've tested the same 10 amp fuse and they are all over the map , I only use the certified fuses with the white lettering embossed in the amperage rating.

[@DENicholsAutoBravado]

+Steve Rob Thanks for the charts, and more importantly for the thinking behind it.

[@stephenarling1667]

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

[@arthurfricchione8119]

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

[@SchrodingersBox]

Ohhhhh, sorry- yes the clamp. Mine is a Snap-On model but any 20A DC clamp will work. Make sure it's a DC clamp though- most clamps you find in a hardware store are AC only.

[@SchrodingersBox]

Incidentally, if you plan on signinig up for my other channel, I strongly suggest you opt for a 40A clamp instead of 20A as I show many other things you can do with the increased range.

[@FranktheDachshund]

Whoa! Voltage drop across a fuse. Sweet.

[@SchrodingersBox]

Yes who woulda thought lol!! But there is enough to detect and its super fast method!

[@crystrezerex2life]

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

[@billgroel4463]

Great video thank you for sharing

[@SchrodingersBox]

Thanks for the visit

[@arthurfricchione8119]

Thank you

[@websurfer1585]

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?

[@SchrodingersBox]

Yes but only for a few minutes. After 5 minutes you should see 100ma or less even on a modern car. You definitely shouldn’t see 2 amps!!

[@websurfer1585]

@@SchrodingersBox Yeah I realise that would flatten a battery within hours.

[@stephenarling1667]

A recording meter can be handy in situations like this.

[@CHIBA280CRV]

Fantastic thanks

[@AGuysGarage]

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? =)

[@DENicholsAutoBravado]

+Rhage73 I'd like for a comment on how it was sucking things down too, but you never know, the owner may have temporarily said, fix the other stuff, I can live without the radio for now, dash removal etc., so expensive! lol

[@PIANOSTYLE100]

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.

[@RickyPisano]

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

[@SchrodingersBox]

Right on! Good to see you back by the way. If I recall you were active here maybe a couple years back then you kind of fell off the planet?

[@RickyPisano]

@@SchrodingersBox I check in whenever I have time buddy. Always something else to learn!

[@tubester4567]

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

[@schrodingersboxquantummeka2008]

+tubester4567 Hahahahaha!!! Nice!

[@estrelladelnorte1308]

+tubester4567 nice!

[@raulf100]

+tubester4567 my wife is a sex object. i ask for sex and she objects

[@johnwillis7965]

that commonly identified as parasitic wallet draw, tubester

[@CHIBA280CRV]

chris johnes funny ass comments , Hahahaha 😂

[@eleanorrigby3038]

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

[@williamhanna5224]

Excellent !

[@JohnSmith-ok9sn]

Thank You! 🙏

[@Sandbag1300]

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.

[@Darren1983uk]

Very good!

[@tomwilson5201]

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!

[@SchrodingersBox]

Sounds like basic parasitic draw issue to me.

[@192ali1]

Thank you for your good and comprehensive video. If I may, have two questions to ask you about this video. 1) When you disconnect the negative battery terminal from car, then all electrical should not be functioning. Why should one be concern about the door of the car being closed? Once one of the terminals of the battery is disconnected then there should not be any current passing through wires. Am I correct? 2) Why did you connect the red terminal, the positive terminal of the volt meter to the disconnected ground terminal of the battery? Thank you

[@SchrodingersBox]

1. because you are connecting the battery through the ammeter. 2. you can do it either way. Polarity is irrelevant in this case.

[@Romulus1001]

I know this is an old comment, but I'll respond anyway in case someone else is wondering the same: In order to read amperage, the circuit in question needs to be under load. If you are setting your multimeter leads for an amperage reading, you are effectively changing your multimeter to be used as a "jumper" wire between the two points of contact, so in this example, the multimeter is wired in series with the battery terminal and the disconnected cable, thereby completing the circuit and allowing an amperage reading on your multimeter. Since your leads are jumpers in this example, polarity is irrelevant because the meter has effectively become a part of the circuit, which is why there is risk in this testing method for inadvertently short-circuiting and damaging electrical components on your car.

[@kenibnanak5554]

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.

[@SkyLinMegas]

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

[@SchrodingersBox]

+Skylin Megas Haha I see you bro..... Got 2 weeks free tickets to the box seats for ya, come and get em!

[@Thunderroad8517]

Hey Matt. thanks for the great video. I have an 05 Chrysler Pacifica that has a draw on the iod fuse. I pulled it and it goes away. Ever ran into this? sure could use some help if you have time. thanks for your time!!!

[@SchrodingersBox]

Never had that happen but I would start with a wiring diagram of the circuit and try to isolate related parts of the circuit to find the draw.

[@Bulletz4Breakfast13]

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.

[@SchrodingersBox]

Yep- also very common on hatchbacks. the wiring at the hinge often gets worn.

[@utubeisshite]

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??

[@SchrodingersBox]

I usually just very simply start with the load components and work backwards is all.

[@johnyaya3599]

Good stuff 😮

[@mikedickman6369]

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.

[@SchrodingersBox]

First, Measuring in series will never mess up a PCM. Measuring in parallel will. Second you would need to voltage DROP across a fuse. Tons of fuses have hot at all times because they are ground side controlled. But yes you could measure amperage the way you describe if you found a fuse that was also carrying current at the time. Probably 2/3 will carry voltage though.

[@stanleytolle416]

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.

[@buddyclem7328]

Stanley Tolle Great advice! Not all Radio Shacks are closed, but most of them are. You can probably find one in your area.

[@averymount2237]

e = i x r e voltage i amps r resistance

[@creativesoftwareconceptsin124]

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?

[@SchrodingersBox]

You could certainly do that. I don’t consider that a fix but it is a remedy.

[@BourneAccident]

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

[@trackrunner11]

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

[@PIANOSTYLE100]

That probaby would save some time. Just thinking.. If both sides have aprox same voltage..the test light would light..probably not unless the voltage was from another source. I doubt that..I'm just guessing. Then we test for the milivolts across.

[@davidlee-]

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?

[@SchrodingersBox]

sounds right to me.

[@todayintheshopbanksy5904]

Matt, are you using a separate sound recorder to capture your voice as you seam to have a tiny bit of lipsync. When you start recording, clap. You can then align the audio spikes of the cameras audio channel, with the audio spike of the sound recorder. This is what the clapper board does. The crack shows up on everything that is picking up sound. Cameras not recording sound will be pointing at the clapper board so that picture and sound can be aligned in the edit. Hope that makes sense. Great videos, thank you for posting them Mike .

[@SchrodingersBox]

+WhitwellMike B Its a KZbin issue with long videos. The sound is sync'd correctly on the original file.

[@todayintheshopbanksy5904]

+Schrodingers Box I did think it might be my connection.

[@vasco2109]

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

[@SchrodingersBox]

I fixed a ground fault that was caused by improper installation. very simple.

[@MiguelSilvaFX]

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

[@zerodegrekelvin2]

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.

[@PIANOSTYLE100]

Former TV tech. I dont do it any more. How does the 1 ohm method work?. I have a vague Idea..

[@zerodegrekelvin2]

@@PIANOSTYLE100 I you are former TV tech than you surely remember the formula V=R*I , to measure current with a meter in Voltmeter mode instead of Current mode where your meter has to be in series with the circuit, the cool thing is if R the res is 1ohm only, then your equation V=1*I thus V=I, so you read on your meter the voltage is the current directly, make sure your resistor has enough Watt to sustain the current. What I wanted to say in my previous post was when hardware design a board, they do leave 1-Ohm resistor at strategic test points so they can simply probe voltage to actually measure current for test purpose without modifying the board. I hope I am clear, if not you can keep searching. More ever, the same technique can be used with a scope to measure current and observe current signal on the scope when one need to see current over time.

[@PIANOSTYLE100]

@@zerodegrekelvin2 1 Ohm ..never did it that way. Since V=I R..Then( I) Current will be V/1..So current would be voltage...I have read your message over..I may have something wrong. Ill be reading yours over. .

[@skochavi6721]

When doing the voltage drop across the fuse method, what state should the battery be in? Does it need to be fully charged? Does it need to be connected as normally connected? I'd guess yes because you need a complete circuit, but in some parts of the videos you have the neg disconnected and I want to be really sure I know what I'm doing. Thank you; this and the first video are helping me so much!

[@SchrodingersBox]

Technically it doesn’t need to be fully charged - a voltage drop will be present regardless but it only makes sense to have battery fully charged because it’s draining while you are doing the diagnostics and you don’t want it to die during that time.

[@skochavi6721]

@@SchrodingersBox Thanks. Gave it a try today - didn't find any changes in voltage. A bunch of the fuses aren't the blade type though so have to think about that. Thanks for the videos! Love self-empowerment.

[@stephenarling1667]

@@skochavi6721 You may need to use a lower Volt range to detect small voltage drop across high amp fuses. There will of course be no voltage drop across a fuse when no current flows.

[@johnalfano8920]

Hi, great video. I didnt catch you talking about cars that actually 'go to sleep' after a set amount of minutes. I have a car with an after market radio that pulls 20 milliamps after the car goes to sleep but stays at 1 volt draw before going to sleep. My two year old battery has been compromised and does not hold a full charge but still shows full CCA immediately after I jump the car in the morning. (I have been suffering from dead battery in the morning and will most likely be dead once again at the end of the work day. For running errands of an hour or two idle in a parking lot the car starts every time. I have had both alternator and battery tested but one battery charger showed my battery will not charge past 50% capacity but yet still shows full CCA. So my question is how do i get the Battery people know that my batter is compromised and doesnt ever get fully charged (I have a short

[@SchrodingersBox]

Draw is shown in amps not volts. What is the draw in Amps?

[@zzzlt]

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

[@SchrodingersBox]

+zzzlt Yes.

[@zxtenn]

I have a 96 Grand Cherokee 5.2 for my bad weather/2nd vehicle with a Optima red top that's 4 years old and my battery was dead a few mornings ago and I dropped battery off yesterday for charge then went to work. I just installed battery and pulled out my multi-meter, on 10 AMP scale I am getting .031 so that is acceptable correct? its not .31 its .031

[@SchrodingersBox]

As stated anything below 100mA is fine.

[@zxtenn]

Thanks, just wanted to double check before I be an unnecessary battery, like you say FIND/IDENTIFY the problem then repair-- From what I have read those Optima batteries can be trouble too

[@petersakleh1812]

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?

[@SchrodingersBox]

What is the voltage drop measured at the load compared to source voltage?

[@johnzarollin2749]

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.

[@teknonut1946]

I have a 2003 buick rendevoix, if I leave it sit more than 2-3 days the battery will discharge from the voltage going to the on star system. I noticed the snow was melted over the antenna on the inside drivers side. I am not using or paying for any features from On star. Is it posible to install a simple shut off switch, or is the problem related to the after market remote start. If I just kill power to the computer I will wind up reseting other things each time I shut it down. I can go out and start it every day but there must be a better way.

[@SchrodingersBox]

What did your diagnostic test reveal the circuit issue was?

[@eurokid83]

One thing to keep in mind about the cheaper hall effect current clamps is the accuracy can be pretty bad. The Snap-On EETA308D is a very accurate hall effect current clamp, it's also quite expensive.

[@SchrodingersBox]

+Chester Wardan I've never used anything but the one I have but that totally sounds reasonable. Cheaper equipment is seldom as accurate as higher quality equipment.

[@eurokid83]

+Schrodingers Box Another way to measure parasitic drain is to use a 1 ohm 10 watt resistor in series between the B+ post and B+ cable and measure the voltage drop across the resistor. I made a test harness with some alligator clips, a fuse holder, and a 1 ohm 10 watt resistor. Works very well and there's no risk to the meter.