I've used an infrared camera to find a draw. Fuses, wires, motors, amps, and control units will show warmer temps overnight when drawing electrical circuits.
If its a modern vehicle keep the meter connected and wait until the computers sleep. Connecting the battery, opening the door handle, many things put it in wake mode. Some cars even prime the fuel pumps or run glow plugs. Also, disconnect the alternator at the fuse on the power box, its way easier and safer.
I have seen several vehicles take a half an hour or more for the computer to time out. One thing I started doing is run a jumper wire between the battery and the terminal in case my meter times out and it goes to sleep.
@wearetheresistanceprepping1883 If your meter times out/goes to sleep, you can just turn it off and back on the amps setting without "waking the system"
@TimmyMill87 not so easy on the fluke 77. It must be turned off then back on and it will reset the system. It's just too easy to disconnect the cable then install a heavy enough jumper wire. That way you don't even need to leave the meter connected, just lay you leads on it from time to time. I've seen some f150s take a hour to time out.
Thanks I have a brother that has been trying to teach me this my entire life. I'm 43 and now I know it because of the way you explained it. I truly appreciate that.
This is great information that will save people money, now that diagnostic time is sooo expensive at the shop. Here's another tip "for the rest of us..." If you don't have a multimeter for an amp draw test but, you still want to take a crack at figuring out what's wrong with your car, use a simple, inexpensive test light that is found at most any store (Walmart, dollar store, grocery store, any store with an automotive dept) for just a few dollars for the cheapest ones. *Be sure it has a ground clip and a probe point,* not just the little, pocket screw driver type. Those may or may not work but, the "regular" type are very useful for many things like this. Hook in a standard test light just the same way as the multimeter. The ground connector end clips to the disconnected, battery ground cable and then touch the sharp, probe point to the negative post (push it in a little to make good contact & make sure the key is off). If you're drawing amps, the test light will glow, though it may be very dimly. Remove fuses or items like the alternator, starter or anything that is connected to the system (all the lights, radios, etc. should be on a fused circuit so make sure you find ALL of the fuses, especially if something has been added in by someone). Remove things from the circuit one at a time and when you find the culprit, the test light will go out. You won't be able to tell how many amps are being drawn as you can with a meter but, that's ok, it's the stopping of the amps flowing that your looking for. Just take your time, find a way to identify where you've already been (mark a fuse box, separate fused wires, alternator, etc. with a piece tape or marker that will show your work) so that you don't lose your place and have to start over and get frustrated and confused. It's easy, just have patience and be methodical. You don't have to be a certified mechanic or "smart" or "rich" enough to own and use an automotive test meter as is shown here... Simple, household tools will work! 😊
Absolutely wonderful job at showing how simple this is! I am about to get my ASE A6. every shop I have worked at despises electrical work. In this competitive market, I will be one step ahead.
That's because you don't make money doing electrical diagnostic they pay an hour for a 5 hour diag. Most tech know how to do it but on flag pay it's not worth it
I just had this happen on a 73 Torino I was working on, & it had a chrome aftermarket alternator on it. I put a two hundred amp relay inline of the alternator wire to the battery, and it would engage with the key. this essentially just disconnected my battery from the alternator when I shut the car off. Works freaking great.
Alternators have ‘diode’ packs within them. Without going into a worm hole how everything works inside the diodes allow current to move one way, from the alternator to the battery.. if one of these fails when the car is off and the alternator isn’t charging the alternator will take ‘power’ from the battery.. draining it quickly in some cases. Newer alternators are complicated beasts but you can test them using a DVM.
First thing I use an amp clamp on either battery cable to protect my meter, then if the draw is low enough the ten amp or milliamp scale. Just as important is to clip the negative lead to the negative cable, then loosen the clamp bolt but do not remove the cable from the battery post until you place the positive probe on to the battery post, then disconnect the cable. This maintains the radio presets and does not wake up the various computers. An aside on radio presets: whenever I replaced a radio or have to disconnect the battery for any reason I always write down the presets, CD channels, and any other pertinent data that would be lost and leave the sheet in the car. It makes for good customer relations and reflects well on you and the dealership.
I've looked at just one video that showed this procedure, However it didn't explain the steps cause an effect no where near like you did here in clarity. Thank you very much for being so clear and precise with your explanations and results.
When you’re doing this it’s advised to keep the circuit closed by using the leads, while removing the battery cable. It’s to keep the modules active so you don’t miss one that turns off and end up chasing ghosts
Clamp meter better if you don’t want to zap your digital multimeter - just think when you connect the negative lead to the battery & the spark you get - that could be a current draw of more than 10 Amps in my humble opinion. Think I’d prob use the voltage method on the fuses - there’s a relationship between the millivolts measured & the current drawn - can’t remember where I saw it but it’s out there on tinternet….
All multimeters have fuses to protect the current measuring circuits, if too much current goes through it, all it does is blow an internal fuse. On the amps setting, its often a 5-10 amp fuse, on the milliamp setting its a few hundred milliamp fuse, depends on your meter. Measuring for voltage drop across a car fuse is nonsense, fuses dont have signficant resistance. If there is a voltage drop it means there is siginificant resistance across the fuse.
@@jumboegg5845 I mentioned I didn’t have a clamp meter at the time - but you go right ahead if you think a fuse is going to protect your multimeter in this scenario. If it’s a $10 multimeter then what the heck eh - not forgetting the aggravation of changing the fuse - some are non standard so you’d have to order one unless ya bodge it to get a job done. You’re then hoping it actually went short circuit before zapping the multimeter - not nice seeing circuit board traces burnt to a cinder due to time for fuse to blow or LCD display gone due to voltage spike. Using more expensive multimeters most take precautions when using on ‘any’ equipment before sticking probes in/on. The voltage through fuses does work - it worked for me - & obviously works for others when watching those mechanic/creators on RU-vid that demonstrated it. It’s slightly more techy - with the different graphs for different fuse ratings - but one can get carried away as it’s not too difficult to find where the current draw is & what value one should expect. I’m ok with it. It’s not rocket science. I think this creator did a RU-vid on the voltage method 🤔 but may I suggest “Which parasitic draw test method is best” by FordTechMakuluko - he covers the bases - & precautions too. There are also isolating battery clamp terminals made with a switch to help protect the on/off scenario of probing with multimeters. They go some way to protect the multimeter - but I’ll make my decisions if/when faced with this scenario again. All the best! Happy diagnosing!
@@messageobliquespe100 Its just how fuses work, a fuse very effectively protects the circuit from over current. If your cheap 10 amp rated multimeter can't actually handle 10 amps (because its poorly designed and overated), then always best to use a lower rated fuse (say 5 amps), to make sure it never works close to its maximum stated rating. The fuses in multimeters are special high energy ones, designed to protect you (not the multimeterr) against high voltage spikes of 1000 volts or more. This can only happen in general use if you are working on mains power, or if the car you are working on is struck by lightning lol. A fuse is a resistor, and because of its resistance, a 10 amp fuse for example will start to get hot and will show a significant voltage drop across it when it starts to get close to the 10 amps, slightly above 10 amps and it will get too hot and melt. That's how they work. So I suppose the voltage drop across a fuse might be useful sometimes, but the voltage drop would be very small, if like for example in the video the parastitic current draw was only 3 amps. 3 amps across a 20 amp fuse would show a tiny drop in voltage. I just went into my shed and put 12 volts 3 amps across a 10 amp car fuse, and measured a voltage drop of about 0.08V (80 mV) across the fuse. Thats very small, but I suppose it could be useful as a very quick check, but only if all other fuses show no voltage drop, and only if there is no legitimate reason for something to be drawing 80 millamps across that fuse.
@@jumboegg5845 Thank you for your comments - all taken on board. Fuses can be effective in protecting the circuit from over current - but you’re at the mercy of the engineer that designed the circuit & specified fuse rating /quality adopted by the manufacturer. (I’ve been down this rabbit hole before - a 5 amp mini blade fuse in an expensive bit of kit that wouldn’t see much more than 1.7 amps at a push/fault when speaking to the service engineer. I imported & used 1 amp fuses - equipment been fine for years. I apply this rule to expensive electrical equipment - even domestic equipment - & down rate the fuse ratings where I feel fit / the need. Simple to take current draw readings from standby to switch on & select on that basis. I’m a bit precious of my Fluke multimeters they cost enough to warrant being careful with. With regards to your analogy of fuse breakdown - ie ‘slightly above 10amps & it will get hot and melt’ - fuses are more robust - can operate well above their rating for a number of hours. Blade fuses will carry on working for 100hrs at 110% of rating - 10mins at 135% - 5 secs at 200%. If there’s additional headroom given to the fuse adopted in the unit you can see how things can go south. I’ve not looked at the fluke fuse & its characteristics. I should put on the list but take for granted they knew what they’re doing so I’ve not bothered. “the voltage drop across a fuse might be useful sometimes” - glad you’re coming on board! The voltage drop is very small - we’re talking measurements in millivolts. In the Charts/tables you can read off the millivolt measurement for the fuse rating & see how much current is being drawn through the fuse/circuit. Search for blade fuse voltage drop on tinternet - Wordpress.com should come up This voltage reading is a measure for the current through the fuse. You can look up the current value in the table. From charts - for info:- 10A blade fuse: Resistance = 8.12milliohm. Voltage drop 116 millivolt -(I think this is maximum value of approx 1.4x fuse rating). For a 3A draw - through the above fuse - you should see a voltage of 25mV. (4A 33mV. 5A 41mV. 10A 82mV) To measure the voltage drop across the fuse, set voltage scale to mV - place the positive lead on one side of the fuse and the negative lead on other side. It takes seconds to do. When you see any value on the multimeter you will know there’s current going through as most circuits will be off or very little current being drawn - so anything greater than say a millivolts or two will stand out - & be a circuit to investigate. it’s a quick method - BUT note what the FordTechMakuluko on RU-vid covers. Hope you watched it 🤔 Approx values - for 1 millivolt:- for fuses:- 3A = 30mA 5A= 50mA 7.5= 90mA 10=120mA etc - Usual current draw in vehicles range from say 40-80mA when ‘shut down’ so over this can result in draining the car battery - which is what we’re trying to diagnose. Let me know of your further shed tests. Happy diagnosing! E&OE (I’m not in my shed)
@@messageobliquespe100 Thanks for all that useful info, you put a bit of time into it. I know the maths and theory so probably wont need to look up the tables, but I am sure they will be very helpful to others reading this. Thanks for picking up on the milliamp "typo", yeah of course it was a voltage drop of 80 mV, not sure when that happened, must have been when editing to improve my expression. I've edited the mistake so its not there now. My experiment was quick and crude, just happened that the first load resistor I found was 2.2R 5W, was getting quite hot in my hands, quickly measured roughly 0.078V across the 10A fuse while holding it all together in my fingers, didn't bother measuring on the millivolt scale, was just after a ball park figure. Just realised my mistake, I initially limited the current output of the power supply to 3 amps, and forgot to unlimit it when taking the measurement. Just checked now and current draw at 12 volts is about 4.9A according to my cheap bench power supply, yeah I know that value is a bit low, when I want an accurate measurement I use a multimeter. In the video, the fault was showing 3 amp draw, which would stand out like a sore thumb. I have found 12 volt relays with corroded contacts passing something like 150 mA when they should be completely open (off). When standby current at the battery should be roughly say 50 mA, an extra 150 mA at the batttery due to such a fault takes many days to drain a good battery, not overnight. Using your values above for a 10A fuse, the voltage drop across the fuse due to a 150 mA fault would be a tiny 1 mV, and even less for 20A fuse.
After you connect the meter, wait ten to fifteen minutes for everything to shut down. If you open a door, trunk, window or turn on the key, you have to start over. Some on board computers stay active a long time. Then check for a current draw. If it's more than 200 miliamps you have a parasitic drain. The first thing I would check is the alternator. A failed regulator can keep the rotor energizer.
@@rupe53 right there with you. Started in my dad's shop. ASE Master tech for over 40 years. I retired in 2017 but did my best to keep up with the technology until then.
@@gener.1253 ... going from memory, but recalling I started ASE cetrs back around 1978 or so. (NIASE?) I kept taking the tests till I ran out of time at the test centers. I did auto, machine shop, service writer, truck, (heavy and light) bus, school bus, carb, and EFI, body / paint, etc. People at that level numbered under 500 nationwide at the time. i was also certified as master tech by Nissan. I finally let them lapse around 2010 when they offered an extension (6 months extra) but failed to let me know when the next test date was. I said "screw it" when my employer didn't want to pay for it. Retired 4 weeks before Covid shut down the world.
If you notice, the meter Reads negative 3 amps. that's because the black probe is supposed to be on the battery terminal. Which is ultimate ground and the red probe goes on the cable. Battery Terminal is Ultimate Ground. Black Meter Lead is Meter Ultimate Groumd. On this Test, the Meter should Never Read Negative (Volts or Amps), fir Proper Diagnostics!!
Good eye! That is correct, I had the leads backwards in this video. With that said, the test works just the same and you would know that it is in fact a "positive draw" if that's what you were looking for in the first place. Thanks for your comment !!
You are Correct, I wasn't Being Critical. My Students get it Confused. With the New Electronics in the Industry today. Negative Voltage is Used In some Control Systems. You Video was Very Informative for A Technician I was Working With. I Appreciate Your Reply!
I came here to say this but yeah like he said any number higher than .50 you know something is wrong. This is exactly what was wrong with my Honda Civic. I think it's doing it again. Idk what's wrong with this car.
@@HumbleHotshotlove the disingenuous back paddling on the INCORRECT amp lead hook up! good job! 🤦♂️ It WILL blow the 20A fuse on a lot of multimeters!
Good stuff in this video. I'd just add make sure all doors are locked with door switches taped down and latches closed if doors are open for fuse access. Otherwise, you could blow the fuse in your meter rated for probably 10amps because of loads active when you unlock the car. If you're trying to find the circuit causing the parasitic draw, start pulling fuses that could be under your dash. Of course depending on the car year make model if this applies to you.
ty so much for this video!! now i can get somewhere on this car cus i just put a new alternator on and it wont crank or has any power but the battery is fully charged🎉
Pulling fuses on newer cars resets modules that can potentially be the culprit. Might make it for a longer diagnosis. I found it easier to do a voltage drop check at the fuses
No they wont, you dont understand electricity. A fuse should have no voltage drop, a voltage drop would mean there is significant resistance across the fuse.
@@jumboegg5845 Exactly, No more than the standard volt drop for wire which over such a tiny distance is not measurable especially not with a cheap consumer multimeter used by someone who doesn't know what they are called.
This is the old method. The newer method is to use the voltage drop against the fuses as the computers can stay awake for 15minutes, its even worse with keyless entry systems. So you have to have the key well away from the car
I just repaired a SLK230 Mercedes with that problem. The battery would be dead after sitting a couple of days. But the alternator was intermittent. I never did isolate the power draw, but I noticed sometimes the battery went dead while running the car. I replaced the alternator when I noticed the output of the old one was low..and after that, no more draw either.
@@georgerivera9220my car is dying out got the alternator changed he uses a old one got a new battery still dies out after a few mins how do I check for a failed engine? The engine sounds perfect?
A DC clamp may not read such a small current draw. The suspect drain is most likely either a bad diode in the alternator or a trunk light switch. Or if you have a light under the hood.
@Dave M it will, unless you get an absolute pos DC clamp or it is very high range luke 1000 amps. A trunk light is likely over an amp. If it is less than 10 amps, then go ahead and switch to shunting the load to measure it. If you have a short you will blow the fuse in your meter this way.
We used to be able to do this test with a lamp, but today's vehicles have so many "normal" petty draws that it doesn't work. I'd add that you also might disconnect the alternator's control plug to see if the draw drops. That would verify that it's indeed a draw from "within" and not possibly an external control signal, possibly energizing the field, or whatever.
Mine was a door switch that would randomly turn on interior lights at night while I was sleeping of course. Took six months to finally have it happen when I was in the car
I did have a parasitic drain. I bought 2, $12 switches on my batteries on my Saturn & F150. No more parasitic drains I can't "fix". I found the drain and fixed both vehicles, but still have switches on I turn of and on. It's a good fix if it's otherwise a mystery.
Did you connect the 2 disconnects to the pos and neg terminals or do you have two batteries and install them on both negative terminals? I need to do this temporarily until I can find the source of my parasitic drain. Thank you
How do you stop an amp draw at the alternator? I recently replaced my water pump and had to remove the alternator and after I put the alternator back in, my battery is at about 12.39V in the morning. Checked the scope and v to starter goes down to 7.5v for the first half second while cranking so engine struggles a bit to start.
I've been working on cars forever and never really thought that alternator can drain.... Thought it just wasn't charging.... Learn something new everyday
Yep, it's not super common, but this does happen! A shorted diode in the alternator will drain the battery quickly since the two are tied directly together. This can happen if someone hooks up jumper cable or jump box backwards.
Surely the curves in our terrestrial nature are caused by the rotation of the earth. The comment he makes about the earth moving out of the goldilocks zone is interesting too, does that mean that mars was once in the goldilocks zone and as such, could have had life on it while earth also had life on it? Does this mean that as Mars left the zone its inabitants could have jumped ship to survive and began inhabiting Earth?
And if you hit the starter while attempting to measure current, you will be lucky to blow the fuse in the multimeter. Bad luck will be to blow the ammeter from the ~300 amps that the starter can draw at inrush.
Dam everyone has a different way dam I'm looking for good advice my brain has an over load from reading everyone different ways ughhh my car dies out new battery alternator was used when replaced shady mechanic didn't tell me it was used charge me 500 now it's dying out after a new battery any advice 2011 Chevy Malibu 3.6 helpppppp
Replace alternator or put in a battery isolation switch. .. better off change the alternator, I you can replace alternator diode pack. The diodes changed 14volt AC to DC.
You have to wait up to 7 minutes on some vehicles for modules to go to sleep before testing or you’ll be replacing a lot of modules for absolutely no reason….. it’s gonna have a 2-5 amp draw until the entire vehicles modules go to sleep.
3Amp draw could be the car waking-up; the 2015 JK JEEP will draw 3A for several minutes, then it will idle-down (sleep) to about 0.020 Amps. So be aware of that - many many newer cars will draw current initially when you first connect the battery - for a few minutes, then the car goes back to sleep mode.
Fuses are a great way to find shorts. You want to do it at night time, you remove one fuse at the time, when you put it back if it arches, this is the short. But their is no fuse for the alternator, but most alternators have a nickel size round metal in the back, when it's running you should have a magnetic pull from testing it with a screw driver, if their is no magnetic pull? It means the alternator is not charging.
Keep in mind that the fuse it's only 10 amps and the peak could be higher. I modified mine just a little (if you do do it at your own risk) and mine can reach up to 20 amps I also have an amp clamp also give it time for the computers go to sleep.
So on one hand, it could appear that one's alternator is fine (i.e. charging the battery when car is on).....but could still be faulty by parasitically drawing power while car is off?
That is 100% correct. This alternator charged perfectly at 14.2 volts with the engine running, but drained the battery overnight due to a shorted diode within the alternator. This can happen if a jump box is hooked up backwards.
@@WildFaith How interesting...thank you! My alternator 5 years old...but car only has 23k miles on it. Aren't they supposed to last waaaay longer than that?
My 04 Chevy truck battery goes dead after like 4 days. I hooked my volt meter up like you and pulled the fuses/relays 1 at a time. It showed 12 volt drain after pulling all the fuses. What do I do now?
I have a 2021 Subaru Outback and did an amp draw test. After an hour of pulling fuses and testing, I narrowed it down fuse “UNIT +B2”, which was pulling 2.3+ amps! Any suggestions before I take it in to be diagnosed?
We pulled the alternator 3 pin connector and it turns out the wire is drawing power snd stays hot even after hours of the engine not running. What would I do in this case? Its a 2003 Chevy Tahoe
Any ammeter, or any multimeter set in the amps mode, should be thought of as a dead short, or just a piece of wire. That is why it must always be connected into the circuit in series with the load.
After gping to 3 different "Pros" and Over $1600.00 & 3 brand new alternators & 3 brand new batteries, I was told today that it's......You guessed it! The alternator again. The "Pros" can't find anything other that to tell me it's the alternator.
I’ve done this test a thousand times and so has multiple mechanics who always tell me the battery is bad after performing this type of test that shows 0.0! I’ve been through 3 batteries and the exact same thing happens. Only one mechanic came up with another possibility that he didn’t think was the case but something about load at start. Any idea what kind of bad extra load at starting could cause a quick drain? I have zero after market parts and I’m driving a 1993 z28 Camaro. Any guesses would be appreciated
Or just the DMM to check for MV across the fuses....this is the way taught in electronic diagnostic class. 😉each fuse has an allowable MV rating based on fuse amperage. 100% guaranteed everytime
Unfortunately “most” multimeters only have a 5 or 10am fuse in them, and most modern cars will draw more than that at battery reconnect, my work truck 22 f250 cycles fuel pump when battery reconnects and evap system, total draw is around 18amps, while momentary still exceeds the meters fuse…….so, buy a stand alone old school needle gauge amp meter like you used to see in Chevy/ford/dodge dashes and use that, they normal can read upwards of 60amps, use it until you can get everything under 5amps then use a modern meter to look for low current draws
Wait a minute 1st run a wire from neg post to neg cable then hook up the meter, remove added wire if it is up over 35 mil amps then hook the added wire back up for a few minutes & let any timers run out then remove the added wire & see what the current reading is,,, Some vehicles timers may run for 20 minutes or more.
Definitely test all fuses first. It takes 5 min and will identify the problem component without guessing. Then u xan directly test the component that has gone off.
