How to Fix Battery Drain in Your Car (Parasitic Draw Test)

How to Fix Battery Drain in Your Car (Parasitic Draw Test)


one, two, three, four! Rev up your engines! It’s time for the Scotty Kilmer Channel if you find that your car battery goes dead if it sits for a few days and won’t start,
then there’s something draining your car battery, and you need to find out what it,
is so today I’m going to show you how to check a battery drain in a late-model
car, now it used to be that you could check for battery drains it was a simple
test light like this. you just get a wrench and take off the negative battery
terminal, then pull the terminal off, and hook one end of the test light to the
terminal, and plug the other one into the battery, and if the test light came on
like this, it would mean something’s draining the battery, but you can’t do
this test on a modern day car, because they have so many computer and sensor
drains, that they always use a little electricity, so you have to be more
accurate, like this, you need to make yourself a little test device with two
clamps, and a resistor in the middle, I bought this resistor at Radio Shack for
two bucks, it’s a 1 ohm 10 watt resistor you just connect it between two wires,
then you connect one end to the negative terminal, and the other end to the
battery terminal, that way this new test circuit connects it, and you can check,
then you get a voltmeter and you connect it on each side, one goes on one side,
and one goes on the other, then we read the voltmeter, in this case it’s between
about four, about eight, or nine millivolts,
now that’s perfectly fine for a late model car, most will allow up to 35
millivolt drain, that’s normal, but if you have a lot like this, if you have a drain
this high, which is three point 6 volts, then you’ve got a serious drain, and you
have to find out where it is, well then you go to the fuse box and start pulling
fuses and watch the gauge, pull the fuse out one at a time, and watch the gauge,
when it goes back to the original small drainage you had, then you know you
found where the problem is, well in this case, the fuse runs the overhead light,
and some knucklehead left it on, so this is a real easy fix,
we’re just turn to switch off, now in most cases it’s a lot harder finding the
drain than turning off a switch on an overhead light,
but as long as you have a voltmeter and this little test wire, you can find any
electrical drain, just remember you need to use a 1 ohm 10 watt resistor, and
realize that 35 to 45 millivolts is a normal drain for a modern car, but your
car may be different, so check with a mechanic to see what the normal drain is
for your car, some late-model Mercedes have a much higher drain that’s normal,
so you have to find out if you’re not sure what yours is,
so don’t let battery drain get you down fix it yourself, and remember if you’ve
got any car questions just visit Scotty kilmer .com and I’ll answer them as soon
as I get back from this ride!

100 thoughts on “How to Fix Battery Drain in Your Car (Parasitic Draw Test)”

  1. ⬇️Things used in this video:
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  2. These videos are awesome, I think I have saved around $8,000 in repairs on my vehicle over the years by watching and doing most myself. Even if I take my car in to have it serviced, I’m not getting ripped off.

  3. Where did you get those alligator clips? or you just used the set of the multi meter and cut them? I'm liking your vids. very informative!!

  4. my car battery holds good charge, but then goes bad after a week, It does this on any car I put it in.

  5. 2009 ford crown victoria police interceptor has a slow battery drain new battery and alternator I i guessing I should try what the video shows

  6. did the test drain (2000 Saturn) and it indicated "IP batt" and "body comp." Did a quick search, but can't seem to find out what these fuses do, to follow it through to what is draining, needs repairs. Do you know where I can go to find this info? Thanks!

  7. Hey scotty i bought my 2013 ford f150 in 2013 its now 2018 when should i get a new battery?i have no issues just asking

  8. I stopped for a moment to consider what Scotty did and why it makes sense. Someone already said it, but I'll clarify.

    Using Ohm's law and a 1 Ohm resistor, you will find that the number obtained for the voltage will also be the same for the current. I'm not saying that 1 V is equal to 1 A; I'm saying that the observed number for voltage will be the same as the number for current, so that if you read 1 V, you will know that the current is 1 A. If the voltage is 30 mV, the current will be 30 mA. HOWEVER, anyone familiar with resistors knows that they have a tolerance associated with them, and there is NO resistor which can be said to be exactly 1 Ohm. Therefore, it probably won't be the case that what you read on the voltmeter will be what you would read on an ammeter, but for this purpose, it might not matter. If more precision is desired, you need a resistor with a small enough tolerance, or simply use an ammeter.

    Finally, if you use Scotty's method (seems to be called the shunt resistor method), you don't run the risk of burning a fuse if the current is too high when the multimeter is used to read the current.

  9. I have a question my voltage keeps dropping when I hit the window switch to roll windows down or when I step on brake it drops I just bought a new alternator and battery still does it I changed my battery wire from starter to battery still nothing ground wire and positive wire were getting hot on battery and my car shut off just turned back on but i think my ground wire might be bad

  10. Hello Scotty.. I tried your method to diagnose parasitic current drain in my car. Unfortunately the 1ohm 10 watt resistor was getting too hot and almost melt before I could proceed any further. My car is bmw x5 e70 and she has excessive current drain before sleep and during sleep. Please advise on how I could improve the diagnostics method. tqvm

  11. What if im using a tester that has 2 different color types, red indacates positive and green is for negative and when i apply mine it goes green and not red

  12. I have a 2006 volkswagen toureg v8 that won't start and has a new battery but dies quickly. It acts like it wants to crank over, but only back fires occasionally. Lights come on and alarm and locks but just won't start up do u have an idea on what this problem could possibly be? Any assistance on what u would think it could possibly be would grately be appreciated.

  13. I have a 19997 Toyota Camery. I was in an a parking garage and my car stopped working. Aa cd that I had not played for a year flew out and my car stopped. After a turned off lights and the radio stopped working I got the car to start. I got home and the radio, even though I removed it, made noises. I got a new battery thinking was ok but today after leaving two hours of work, I tried to charge my phone in the cigarette lighter and within five min. my car would not start and I could not start car. I am a preschool teacher and if it does on way to work I will be late which is not ok. I am not sure if I sure take the bus or go check with a store about fuses. Help!

  14. Inaccurate title. This only shows how to figure out what is draining power. Doesn't teach anything about how to fix the problem

  15. I have a 2012 dodge avenger i replace the old battery with a new battery and it wont start the dash board light wont turn on, the front lights wont turn on the inside lights wont turn on when i press the key fob to unlock the car it wont unlock or lock at all also when i try to booster jump the dash board light would come on but it wont crank at all do you have any idea what can be wrong?

  16. What brand is that multimeter? Thanks for all the great videos. Hope you had a very merry Christmas and a great 2019. Keep them great videos coming scotty. I've learned alot from you.

  17. My car won’t start unless I jump start it the battery is getting drained but I don’t know why
    If I jump start it and turn it off right away I’d have to jump start again

  18. The problem is as soon as you open a door, a number of small computers become active. They will turn themselves off in about 1 hour. You need to install your 1 ohm resistor, close ever;y thing, an hour later measure the voltage.

  19. Hi Scotty, I have a cabin light battery leak as well. The thing is that the lights are indeed off. The leak stops if I remove the cabin light fuse. Any idea ?

  20. I have a 2007 Hyundai Azera and it sounds like the battery is dead when it cranks and then it stops what could that be

  21. I had a parasitic draw once, took a while to figure it out, incredibly frustrating always draining more and more but I finally left her and have been great ever since ! 💥 🤷🏻‍♂️

  22. Hi I have 2002 bmw 745i I have a battery drain and don’t know what it could be I change the alternator starter and charge the battery I don’t know what it could be help any one
    Thanks you

  23. Scotty. Great video. It's amazing all the internet bozo mechanics on here that critique what you're saying like they know what they're talking about, when they were probably born when you were a 20 year mechanic already.

  24. I brought my truck to get an alignment. The guy told me i Installed the control arms on the wrong sides. So I switched them at home. Then later I went to start the truck and the battery was dead 9.5 volts did they do something? I immediately got the battery on a charger overnight. The voltage returned and it's been working fine since. Do shops have a way to kill your battery?

  25. i have a 2003 dodge dakota 3.7 ltr engine and the radio is draining the battery what can cause the radio to drain the battery when the engine is off?

  26. Scotty will answer your questions, most others on here who will remain nameless as they should will not..

  27. Thanks a bunch Scotty. We we finally able to track down the parasitic drain on my wife's H3. BCM module.

  28. Scotty my corolla 1994 battery is draining really fast. It wont start the car. Should I check the fuses only?

  29. Scotty knows $5 metrrs from harbor fr or anywhere have amp or current functions..really asinine to not utilize them if labor is valuable then resistor shopping is ..oh never mind knock yourself silly

  30. Thanks scotty. I'm having this drain problem. Will try it.
    Ps
    I watch all your show just to understand car more.

  31. Just don't try to crank the engine with your resistor in the circuit. I-Squared-R (I^2xR) will get you every time. 🙂 And should you have said resistor on the paint or plastic, it will leave a memento of the event for you. The same applies to your fingers.

    I've got a Fluke 87 that will measure the current directly, but Scotty's way is every bit as good.

  32. Depending on your multi-meter You could actually just place your multimeter in sequence with your negative battery terminal and negative batt cable. Then just wait 30 mins and check to see what your drain is. After 30 min of waiting for the cars computers to turn off, an acceptable drain would be .003 mv, anything more, you should test your fuses with your multi meter. That way you dont have to unplug all your fuses.

  33. Where can a guy get a Tester like that? I Have a Zurich ZR13 tester. I got a huge drain Batteries on a 2003 Ford F250 6.0. Drains very fast within 20 Mins of driving Radio goes out and Truck runs run like it misses?

  34. Dear sir ,

    Car was running properly, but when I came to parking and parked the car and went to Reverse gear , reverse gear tone was not working properly and all of a sudden Battery drained completely…

    Car was running good since a month , suddenly battery problem..
    Totally drained ,
    No indication light in Odo meters
    How sir?

  35. Baguih naaa hang buat video yang bagi manfaat kat orang lain… walaupun entuism nampak lebih, kira ok lah xmcm saya passive, nak shows,all out tak sampai 100%. 50% pon x. Bukan below average lagi dah, below abnormality.

  36. Just wanted to say hey Scott kilmer and thanks videos on all the how to repair videos you neve stop learning and always ask questions and i see that you have a bike also one ill get mine out ans riding god bless brother

  37. Uncles cars drains battery very often we dont know where the promblem is we have call electrician to check but he says there is no anything drainning it but when we park it next two to three day it cant kick again wats the promblem

  38. Check your resistor with your ohm meter clamped on. If the ohms reading of your little circuit is 1.0, your amperage will be the same as your voltage reading. If like mine your circuit is 2.3 ohms, caused by the test leads not the resistor, you divide the voltage reading by 2.3 according to Ohms law which states the current in a circuit is directly proportional to the applied electromotive force, and inversely proportional to the ohmic resistance.
    I (amps) = E (volts)/ R (ohms) My truck is pulling 46 milliamps with everything turned off and so far I have not found the problem. It is an old truck (1992) and should not be using this much current.

  39. That's a whole lot for this video! One of our work vehicles has had a drain for more than a year. We have to start it up and take if for a drive every three to four days or it won't start. It has a new battery, that I recently had tested along with the alternator. There must be something draining. Now I'll be able to check for the drain, while avoiding an expensive auto electrician.

  40. at what do you set the multimeter ,if i mesure voltage i am getting 12.84v same as battery terminals. the first time i pluged the resister betwen neg battery post and neg conector the resister came realy hot and smoking

  41. I need help. my 2001 Buick century has this problem and I always need to jump start it after like 10mins of shutting it off. I’m not sure where the battery drain is coming from but Iknow it’s somewhere

  42. I'd like to try this method but I want to mitigate what a short power outage may do to the cars computers, radio etc. when I remove the negative battery cable. I am thinking of connecting my OBD2 12V power adapter that I use when I replace the car battery, to provide temporary power while I connect Scotty's parasitic draw test cable, then removing the power adapter while testing and do the same in reverse done.

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