Battery Keep Dying? Simple Tests For A Battery Drain (Parasitic Draw)

[Music] hey welcome all right so you have a battery that ends up dead on your vehicle maybe overnight or maybe it only takes a couple of days type of thing and the battery itself has been replaced maybe you know that the battery is good it tested out just fine you know that the starter and the alternator that they're both okay they're not causing any issues for you what you're looking for is how to figure out maybe how to determine what is draining down that battery this is called a parasitic draw and just like any other parasite a parasitic draw is draining current from the battery when the vehicle is supposed to be off and not doing anything at all your battery should last uh quite a while it's going to depend on the vehicle and the reserve capacity of the battery but realistically this 2000 corvette behind me should probably still start up after it's been sitting for two weeks i can't even let it sit overnight right now and uh without the battery going dead okay we have to jump start it basically every time the customer wants to drive the vehicle at this point so um the vehicle itself for this test doesn't really matter you guys can apply this testing to any parasitic draw test so the first thing that we have to do is we have to determine if there actually is a parasitic drum what this is going to require is a meter that's able to read amperage okay and what we're going to do is we're going to take our meter and we're going to insert it into the system and what this means is we're going to run the meter in series with the battery cable so we're going to take and disconnect the battery cable from the negative and the cable itself we're going to attach one meter lead to the battery negative one to the battery cable itself and now our meter is in the middle so all of the current leaving the battery is going to be measured through our meter now be careful here because most meters only have a 10 amp fuse okay and if you do something as simple as opening the door it could wake up a bunch of modules turn on a bunch of lights and pop there goes the fuse so you can see here i have the vehicle all prepared for parasitic draw test and what that means is i've opened all of the doors the trunk the hood and i've manually tripped all of the latches so right now as it sits the vehicle thinks that all of the doors hood and trunk are closed when in all reality i have them open for ease of access to different pieces and components on here okay so always do this because you don't want to open a door when your meter is tied in series to the system so this vehicle here is reading 525-ish milliamps of a draw that is half of an amp of draw is that good or bad well i've already told you that this car ends up dead overnight so we know that 500 milliamps is bad the specification or rule of thumb here that you want to be looking for is under 50 5 0 50 milliamps okay that's a tiny tiny number to put that into context for you guys a glove box light or something like that may take about 250 to 500 milliamps okay we're looking for 50. it's incredibly small so we have uh roughly 10 times the spec right now and that's why this battery is dying overnight so what do you do next we know we have a parasitic draw we know we have something killing this battery but how do you determine what it is well first thing first do a visual inspection make sure that there's no lights on when you're dealing with a half an amp draw there could very easily be a light left on somewhere make sure that there's no lights on that's the simplest thing to do but the next step is going to be figuring out what fuse is feeding power basically to which component that's staying on so we have a fuse box under the hood here which i've already checked and we have a fuse box under the passenger side of the dash behind the toe kick on here and i'm going to show you guys a really good way to test the system without waking anything up without causing a disruption within the system because the worst thing you can do is pull a fuse and see if the draw went away and then put the fuse back in because now you've potentially just woken up a whole bunch of things and you've caused your draw to actually go up here let me show you so we're 520 or so right now let me pull this fuse and it should go down great it probably went down there and we reinstall it and if we look at the meter again now we're at 955 so we went from 500 to almost 1 amp of total draw now we have to wait for the system to go back to sleep we have to wait for it to go back into that mode that it was before which some vehicles can take 30 seconds some vehicles can take 30 minutes who knows depends on what modules you wake up and what the protocol is the procedure is for them to go to sleep so you can see here in just the 10 seconds i've been talking the vehicle has gone back to its uh its original position here at about 500 and it's actually at 590 milliamps right now so we're still a little bit higher than we were but it didn't take long to get back to that point so what should you do if you don't pull fuses and reinstall them what should you do well if you're fortunate enough to have two multimeters one to sit on here and read the amperage and another to read voltage you can perform this test really easily if you only have one multimeter you can reconnect your whole battery system leave the car sit for 10 or 15 minutes or whatever it took to go into sleep mode originally and then you can start poking around with the multimeter finding out a voltage drop across the fuses so what does that mean well if there is current flowing through the system there's going to be voltage drop across the fuse because there's no such thing as a perfect fuse a fuse will always have a tiny amount of resistance and we flow current through that tiny amount of resistance we're going to drop voltage across there now we're talking a minuscule tiny minuscule amount uh maybe two to four to maybe up to 10 ish milli volts across that fuse that is a tiny minuscule amount but it's higher than zero anything higher than zero is telling us that we have current flowing through that fuse at that point if it's zero we know we have no current flow that fuse could be very high resistance but because there's no current flowing through that system at this point the fuse will read 0.0000 as soon as we flow current through there that tiny amount of resistance will act up and it'll give us a voltage output reading so what does that actually look like in practice here let me show you okay so you can see here we have our multimeter set on dc voltage if you have an auto ranging multimeter great if you have a manual ranging multimeter make sure you're looking at the smallest possible value that you can you can see here we have three decimal places after zero what we're looking for here is an incredibly small voltage reading so i have my two probes here and what i'm gonna actually do is probe each of these spots on the fuses so there's the little metal tabs on the top of each of these fuses so i'll take one lead there and one lead on the other tab and it should read 0.000 all day long that means we have no current currently no current currently current currently we have no current flowing through this fuse at this time so what we'll do is we'll check each of these fuses and i'm not going to bore you guys with going through every fuse in this fuse box but this 10 amp fuse right here is our problem child see that three millivolts a voltage drop across that fuse but any voltage drop across that fuse means there's current flowing across that fuse at this point so looking at the fuse cover here this is fuse number four that is for the s c m l gotta love acronyms on a fuse box but doing a little bit of quick digging here this is for the driver's side seat module so looking at a wiring diagram here you can see that this scm-l fuse this 10 amp fuse is powering up our driver's side seat module so we're not um we're not controlling the powertrain control module or body control module or any sort of critical system with this so i'm going to go ahead and pull this fuse and see what happens to our draw so right here our 10 amp fuse fuse number four on this car pull that guy out and what does our draw do oh wow instantly we are down to 20 17 to 22. um definitely under 25 milliamps here that's half of what our rule of thumb or our specification was and to me that's really what i want to be what i want to be seeing on a car like this so right now this battery won't end up dead so next step would be get the battery all charged up and um determine what the customer wants to do with this so driver's side seat module this is a power memory seat on a 2000 corvette so chances are that assembly is going to be rather pricey it's really up to the customer at this point to figure out what he wants to do does he want to dig in further on this system or does he want to simply pull the fuse out and and let the seat sit in its position where it is anyway so uh maybe depending on if he wants to go further maybe there'll be another video coming up here on diagnosing the driver's seat um causing a parasitic draw but i just wanted to get you guys to understand how to perform a parasitic draw test and how to do it efficiently so you're not pulling and replacing fuses and waking systems up and causing a lot of problems voltage drop across the fuse is going to be your quickest fastest way to do it so i really appreciate it guys make sure you subscribe to the channel if you have not already click on that little bell icon there that way you can get a notification with uh every video that we come out with so really appreciate you guys being there thank you so much and as always happy wrenching everyone thank you [Music] you

Channel: GoTech

Views: 125,016

Keywords: battery drain, car wont start, car battery drain, battery goes dead overnight, battery dies overnight, battery drain test, dead battery, parasitic draw, parasitic draw test, how to test battery for parasitic draw, battery losing charge, battery wont stay charged, parasitic draw multimeter, how to test for parasitic draw, car battery drains overnight, car battery keeps dying, how to test for amp draw, battery test, diy auto repair, low battery, car wont crank

Id: HqxB4Ete17I

Length: 10min 31sec (631 seconds)

Published: Thu Feb 24 2022