How to Test an Alternator (fast and simple)

[@leobonin6415]

HAVING BEEN A MECHANIC FOR OVER 49 YEARS AND A.S.E CERTIFIED MASTER AUTOMOTIVE TECHNICIAN FOR OVER 35 YEARS, I FOUND THIS VIDEO TO BE VERY HELPFUL FOR THE AVERAGE DIY PERSON SAVE BIG MONEY ALTHOUGH IT HURTS MY SHOP BUSINESS, BUT I WOULD RATHER SEE PEOPLE GET WELL INFORMED INFORMATION,RATHER THAN SCREW SOMETHING UP AND BRING IT TO ME WITH MORE ISSUES THAN THEY STARTED WITH, I HATE FIXING SOMETHING THAT SOME FOOL TRIED TO FIX BUT DIDN'T KNOW WHAT END OF A SCREWDRIVER TO USE

[@tinman1955]

Which end of the screwdriver do you use? 🤣

[@leoantonio]

You don’t have to yell.

[@yousuck5314]

@@leoantonio lol

[@EitriBrokkr]

Clearly you're not certified to use the caps lock key

[@thelevophed]

Boomers never turn off the caps. It's the dead give away that this man is truly over 60...shit I trust him off this alone.

[@petersack5074]

As an older guy ; NAPA....i see on the battery. Experience shows, sometimes, that NAPA = Need Another Part Again. ....Not always, though. Sometimes.....they ' get it right ''.....Good video...young man !

[@jjnova71]

This is the most clearly explained, concise, and thorough video I have found on You Tube. Now I'm going to test my alternator armed with the correct info. I appreciate the effort. Thank you

[@AaronHinesAuto]

Thank you for the support!

[@jhenry0688]

@@AaronHinesAuto maybe this is a good video for experienced or intermediate folks but not really much help for beginners.

[@jhenry0688]

@@AaronHinesAuto this isn't good for me because I'm fairly novice at testing electrical & charging systems. Most videos I've seen test everything from the battery terminals

[@petep.2092]

@jhenry0688 You're right, it's difficult to recognize that something isn't working right when you don't know what the normal operation looks like, and it would be quite difficult to follow this video without an understanding of some basics like: - what is a circuit? how does it work? - what is a ground? - what is voltage? how to measure it? - what is an open circuit? a short-circuit? - how is an open/short identified? - how a battery works, how it can fail, - how an alternator works, how it can fail, - how they are connected in a car, - why both are needed and how they electrically power the car, etc. Without that education, you will likely not know how to proceed when you find that the video doesn't exactly match your car's wiring or connection points or you get different test results which are not explained in the video. But it seems you already recognize that. So, look for videos on those basic topics and if you don't find a video on a topic, ask someone who knows to explain it to you. Once you have that basic education you'll be able to learn from this video and more complex ones-on your own.

[@Hugh-Jorgan]

​@jhenry0688 he is explaining every step and showing you where to test at. It's broken down barney style. It's as simple as it gets.

[@sptrader6316]

I'm an old timer, I used to work on cars from the 60s-80's. My easy test for an alternator, is to remove a battery wire. If the car keeps running, the alternator is good. After the car starts, it is running on the alternator. I also check battery voltage, 14v minimum, when the car is running. When an alternator is bad, it's usually the brushes that burn up. Either replace them yourself or take it to a small motor shop to have it done, it will save big money over alternator replacement.

[@kentbarger8628]

Remember the battery terminals on a generator to was one of the ways to find out it was generated was good but when it comes to alternators you you can blow the diodes up in the alternator if you take off the battery post with the car running especially now the alternator system is setup with the computer now how many cars now the computer shuts the alternator off and turns it on heading if you're going uphill or on flat land or going downhill do not want to take off the battery terminal when the car is running this is not 1960 anymore

[@justmejm]

@@kentbarger8628 😂😳 be nice

[@kentbarger8628]

By taking off the battery terminal on an alternator you can blow the diodes in the alternator that is a fact if you do not have a battery and charging analyzer you can use a voltmeter also everything is computerized now in the old days you can take off a terminal on a generator not a alternator you run a big chance of damaging the diodes in the alternator by taking off the terminal I'm a retired auto mechanic my father had a garage since I was 8 years old working on cars all my life

[@jjjohniee]

Wrong, not all cars keep running even with a perfect alternator so you could easily get screwed over if you assume this is correct, it isn't, best thing is to check a car when you buy it, if you have no issues with it even if the alternator doesn't run it on it's own, all good!

[@fineth9319]

Dont do it on new cars. It will fuck up more things.

[@javeedsultan8484]

Very well presented With some cars the alternator isn't easily accessible from top of engine bay I've used this trick with constant results when suspecting a faulty alternator Simplest way without a volt meter to test where the fault may lay is Take precautions as you are dealing with electrics 1) visual check of cables on battery and back of Alternator, give battery cables a slight tug and state of battery connections If loose wire then reconnect if dodgy battery terminals then clean them 2) visual check belt, use the finger test, should be slight give, but not to much To much play means belt could be slipping, if to tight it can destroy the alternator, adjust or replace as needed 3) with car running turn on head lights, rev the engine slightly lights will brighten a bit If the alternator is at faulty you won't see any different in light intensity 4) with engine running disconnect the + (normally red cable) engine should still run with battery disconnected No electric being produced by Alternator so cars electrical system fails due to no electric Simple test than anyone can do even at the road side with no tools but a small adjustable spanner needed to preform these tests Hope this may help if you break down on route, or even a testing at home before buying a test meter unfortunately some road side Mechanics will blind you with gobbledegook knowing you are stressed and just want the problem to go away These four simple testes will help even if you are not Mechanically minded and could save you hundreds, if not thousands of unnecessary work

[@everythingisenergyenergyis3801]

Thank you!

[@huongyn8808]

Thank You!

[@allanturton1637]

This is the first I've heard of step #4; could you please explain that for me? Or provide extra resource (internet link etc.) Thank you!

[@javeedsultan8484]

@allanturton1637 step 4 Start by making sure everything is switched off, i.e lights, radio, wipers, ect... Now start the car and then remove the positive cable ( + normally red) from the battery The car should still be running, even though you have disconnected the battery If the car dies as soon as you disconnect the battery, then the alternator isn't chab

[@1EagleDave]

ARE YOU THAT SERIOUS ??? THIS IS INSANE TO SAY THE LEAST BUD THIS IS NOT THE GENERATOR DAYS THIS IS ALTERNATOR THIS JUST PISSES ME OFF TO SEE THIS GARBAGE GET IT RIGHT OR DONT EVEN MISLEAD PEOPLE AS THIS THREAD IS ALL ABOUT GET WITH IT OR LEARN IT >>> WOW!! >>>> DO NOT DO THIS PEOPLE >>> 4) with engine running disconnect the + (normally red cable) engine should still run with battery disconnected No electric being produced by Alternator so cars electrical system fails due to no electric

[@dalemarshall2935]

You might want to mention cleaning the battery termlnls. This was an issue for me that i figured out on my own. But this was super helpful. Thank you. Saved me lots of money.thanx again.

[@donharrus9994]

🤔 I thought he did

[@thatswhatshesaid6326]

My sons (17) car just stopped running the other day while going to school. I have his battery charging right now. I’m just trying to do a process of elimination. As a divorced mom of 4 teenagers (19,18,17 and 15) I’ve learned to do many things on my own or at least narrow it down. So wish me luck that I find out the issue. 🤞😉

[@yadiratackett7897]

I'm going to help my son also he has a chevy 1990 s10 truck and this truck was passed down from my daughter to him I helped her fixed it when she had it, now my son has it and it starts and doesn't start and it's time to help him know, been a single parent for over 15 years and I have learn to do it on my own. Well hope you got your son truck running

[@BillyBlaze7]

strong and independent

[@brandenjuan5735]

How many baby daddies just curious

[@BillyBlaze7]

@@brandenjuan5735 4

[@JoshuaCastillo6309]

How many inches are you? Just curious.

[@ryanrpalkovic]

I shorted my negative battery post to a relay when trying to reattach my negative battery cable. Some dumbass put a non shielded relay too close to the battery. (me!) a few days later my jeep died on me while driving and wouldn't take a charge. Your suggestion of a blown alternator fuse saved me many dollars and a lot of troubleshooting. Thanks!

[@jerryking8877]

Also, to properly check the status of any alternator's ability to perform its desired function in any automotive electrical charging system, you again simply set the digital multimeter to the continuity test/ diode check setting (marked by the electronic symbol that denotes a diode on your multimeter using a black line disecting a black triangle from its widest end, emerging from the triangle's pointed end which is marked with a short straight line that runs inversely to the 1st long straight line as it emerges and continues past the triangle's pointed end). Remove the alternator's positive 12volt power supply conductor from its positive 10mm bonding stud. Place the negative black lead of the digital multimeter on the alternator's positive terminal while touching the red positive lead of the digital multimeter to the alternator's negatively grounded housing/chassis. You should see a reading of .5 indicating the voltage drop across the diodes of the bridge rectifier ".5 is the voltage drop necessary to turn the bridge rectifier's diode array on". Readings between .3 to .7 are considered the absolute minimum and maximum limits you should see with an alternator functioning inside of its allowable operating limits, however a reading of .3 actually indicates an extremely weak and failing bridge rectifier, where a reading of .7 generally indicates a bridge rectifier that is about to also fail. The reading of .5 is really the desired target measurement here. Now reverse the leads of your digital multimeter, now placing the red positive lead on the alternator's positive terminal and touching the black negative lead to the alternator's grounded metal housing/ chassis. The digital multimeter should read "O.L." (indicating "Over Limit), which means that the bridge rectifier is preventing the reverse flow of current from the battery to the alternator as desired preventing the meter from detecting any measurements or reading at all. Any reading other than "O.L" (Over Limit) here indicates a failed bridge rectifier, which in turn means a failed alternator.

[@christophercarmody2504]

this comment is a master class in concise use language! thank you for being very clear and conscientious. was watching this going "but where does the black lead go??" i'm about to stitch screenshots to get your whole comment in one image for reference

[@MarzNet256]

Nice. I replaced my alternator this morning.I cleaned all connections first and the problem persisted (low charging). It's a 2006 Toyota Matrix 4WD with 208,000k miles.And as you said, always check ALL connections and fuses first.

[@bobatbilletcreations]

Thanks buddy for a great tutorial of checking the alternator and battery....Your time and effort is very much appreciated! It helped me tremendously!!!

[@stevenfreiberg1338]

Im a 62 year old weekend warrior that commends you for a very well made video! Keep up the good work! Sincerely Steve

[@brandonbell5357]

Called rehab

[@kensmith7648]

Old school, with no meter, you can check alternator by starting vehicle and disconnect positive battery cable. If car keeps running your alternator is OK. If car dies it is not .

[@bigsmokedgj1043]

What my friend James just did today and yea it stopped running 😢 said a trick his pops told him

[@abie_irabor]

Yes, AAA tow guy did this for me the other day and he said this same things…it’s the alternator. I thought it was just my battery. This was def a confirmation. Thank you!🙏🏾

[@jefegarpez6505]

Yeah, old trick. You can mess up your ECM or burn your whole wire harness

[@Skye75]

Thank you I will try this.

[@MrOiram46]

But what if my car’s engine won’t even crank and start?

[@Louis-qi1gz]

I was taught this over 45 YEARS ago but it never gets old 🔧👍🔧

[@Wesmancan]

Why would you watch this

[@davehoward1753]

Daughter got stuck with no batt power on freeway. I suspected Battery or Alternator 95 Avalon. This video allows me to test both before going to shop. Thanks.

[@jasonbradford8616]

[@jimtindera1082]

Nice presentation. Spoken clearly and concisely. Even though I’m not the brightest bulb on the tree , it was rather easy for me to understand and comprehend. Thank you. I learned some stuff from you!

[@jimbeauprez8235]

Explained well and kept it simple for the "mechanically challenged ".

[@MrAvant123]

Top tip if you dont have a multimeter, start engine in dark garage, switch on all the lights and as much other stuff you can blower heated screen etc, with the engine at idle, blip the throttle and watch the headlights, if they get immediately brighter your alternator is okay.

[@peggystaat2646]

Absolutely fabulous steps to diagnosis and so very clear - bless your heart and all who help us as you do!

[@Leo137156]

Thanks man, I just used your techniques and found the problem, after checking the battery and the alternator, like you did. The wire connecting the starter to the fuse box was not making a good connection, so I replaced it and it cranks up good again. I had replaced a battery earlier, so I saved a lot. Thanks again. Leo

[@johnbennett7065]

Most informative,without being over technical for the average motorist. Will definetly purchase voltameter.

[@ImportantMan1]

You’re the man. I just fixed my F350.

[@joeygemini6390]

Thanks. I downloaded this video because of your comment below.

[@I.LikeCars]

5 years later, I used your tutorial. Thank you!

[@sharonengebretson3164]

Thanks so much! Clear and very informative. Just what I was looking for but didn’t think I’d find.

[@danielwiggins4960]

This is a real nice video for a weekend warrior like myself who knows less than I believe. Easy to hear and see. Thanks!

[@Wet_Z06]

Literally came to youtube searching how to diagnose an alternator and left learning so much more! Awesome video! Thanks

[@marshalltsien]

great video , very clear , concise and to the point, sum utube videos ramble on n on with nothing to clear and super annoyance. keep it coming , please , happy new year !!!

[@user-hd1qx2bd1r]

Thanks Aaron, the Alternator Discharge Light came on, and I keep my Toyota truck well maintainenced and loved, but you're right of course, I forgot to look for an inline fuse, which I'll do before I test for a bad alternator, Thank You!!!

[@fernn1599]

very informative and you made it very simple to understand! My car is acting up and it's on battery saver mode since Wednesday. We replaced the batter yesterday and it didn't resolve the issue. I am going to do exactly what you did on this video, testing both battery and the alternator. Wish me luck!

[@WadeHufford]

Great video. Very educational simple and to the point I can’t stand the videos with all the theatrics. Good job.

[@davidpotter7484]

This is the best way to test an alternator. Same for the battery, with an addition of an old style battery load tester.

[@TruthLifeFinder]

Very useful and simple to follow. Many thanks

[@jaybraddock2350]

Also check the belt tensioner pully and arm. A weak one will also mess up the alternator if the belt is not tight enough on the pully to the alternator

[@MinhTran-tj4wq]

Nice job! I ran into a case where testing voltage at the Alternator’s stud provide a good reading but was not at the nut of the stud. There were corrosions between the bolt and nut that caused a problem (symptom like an open wire).

[@lostinmyspace4910]

When testing the nut on the alternator with the positive lead of voltmeter, the black wire of the voltmeter gets connected where?...to ground on the body of the vehicle? or the battery itself?

[@petep.2092]

@lostinmyspace4910 It depends on what you're testing. To check voltage drop between ALT+ and BAT+ with the engine running, the black probe goes on BAT+ and you should see 0V, indicating that the connection is robust and can carry the charging current, i.e. it's not hanging on by the skin of its teeth. To check for full ALT to BAT connectivity, with engine not running, red probe on ALT+ and black probe on BAT- you should see 12V (battery voltage) which indicates that the charging circuit has continuity, both the + charging line to BAT+ and the ground path from ALT case to BAT- are good. (Attaching the black probe to engine block or chassis will not have the battery involved and so the test will not provide assurance that the alternator will charge the battery).

[@paradoxdea]

Beautiful video, youg man. Now that's good old-fashioned troubleshooting!!

[@lindsaymitchell5984]

You just save me 400 bucks! Thanks man 😘

[@mommommy6135]

Thank you very much for the clear explanation. Showing and explaining the way you did . 👍

[@majikmae2615]

Girl here, and your video 📹 is extremely informative 👏 👌 🎉I'm still trying to figure out what is going on w my van

[@1dd434]

Thanks for your time to make a great video, very easy and informative.

[@JoHernandez-is8hz]

Thank you for sharing, it helped me alot, now i know, what to look for and ask the mechanic.

[@muhamadsunasrisamat7368]

Very excellent explanation and fantastic. Now i can check my marine generator.

[@ErickSaucedo347]

I appreciate your time thank you. 🙏

[@bobcurran1349]

Nice job Aaron. Exactly what I needed to know plus some valuable info!!!

[@thetheDMT]

gr8 joB Aaron, concise & through, excellent delivery, much appreciated ✌️

[@gordonbarclay6106]

Great video by the way. So near the end of the video you have the probe at the positive terminal of the battery and the other on the casing of the alternator and it reads 12v if you get nothing is that a faulty alternator then. Just fitted a new alternator 6 weeks ago all of a sudden battery light has come on its doing my head in. Really doing my head in..

[@petep.2092]

Probably not. Assuming you have a negative chassis ground… No voltage between BAT+ and ALT case (but you get 12V between BAT+ and BAT-) means the negative ground connection between the battery and alternator is bad. The alternator is grounded to the engine block via its mounting bolts, and it would be unusual for that part of the circuit to go bad, but with enough corrosion it could. That leaves the BAT- connection to the engine block, where it is usually grounded to provide the least resistance for the starter motor's ground return. But some have the BAT- grounded on the chassis, fender usually. Check the heavy gauge wire for proper crimps and clean terminal lugs at the battery end as well as the engine block/fender end, grease, dirt and rust make for a poor circuit. Also check for abnormal lack of stiffness of the cable anywhere along its length due to internal breakage of the copper strands. An open circuit in this part of the wiring would show as nothing working while the engine is no running… won't even start. If it is grounded to the fender there should be a grounding strap between the fender and engine block, usually a flat braided strap about 1 inch wide and 1/16th inch thick, tin or nickel plated. Same checks for continuity, clean, etc. To help determine where the open circuit may be, put the meter's red probe on BAT+ and then sequentially place the black probe on BAT-, then the lug of the grounding wire, then the lug of the grounding wire at engine block/fender, then engine block (fender), etc. moving progressively to the case of the alternator. You should see 12V at each point. When you see 0V, the open circuit is between that point and the last point that had 12V..

[@mikedavis7312]

Thanks man I learned a couple of things very good info

[@nahhtoo7046]

Very nice presentation keep up the good work, I learn from you appreciate you

[@frzmck5900]

Thanks bro for the video, it helped my pop and I figuere that our alternator and batterie are working.

[@RichadTheLionHeat]

Absolutely excellent detailed, informative, great pace, basic ground level fundamentals are critical. I just acquired a 1970 VW Beetle convertible. It’s having some issues with the alternator charging the battery. It is extremely helpful and greatly appreciated. Thank you for your time, dedication, effort, sharing your knowledge with others. I am sharing this with many many people. 👍🏻😉🇺🇸🙏🏻✝️🇺🇸🙏🏻✝️🇺🇸👍🏻😉.

[@LaTuyaa]

AWESOME Video, thank you so much!!!

[@caseyostrander503]

This really helped me out today - THANK YOU!!!

[@JohnPooley-te9ei]

Nice1..Aaron & thank u

[@apexlegendssossagng3079]

Still here checking out GREAT INFORMATION THANKS 👌🏾👌🏾

[@johnleece3356]

I'm definitely going to try this in the morning I have nothing but problems out of my 2011 Honda Odyssey

[@john-e1j2e]

Thanks Aaron. This helped me big time! Very good video

[@bbulliard]

Super excellent world class video. Thank you so much

[@TheMayatchico]

Thank you for this video. Its very helpful. God bless!!!

[@lecobra418]

Nice explanation, especially the fuse tips, I think my alternator died but I'm still not sure, I was stranded with my wife and kids yesterday, it just powered off while driving fortunately it happened on the mall center parking lot so I managed to simply buy a new battery on the fly to get back home. I'm sure the battery is perfect because it's a new one, I will check for excessive dirt on the electrodes, but I'm pretty sure it's an alternator issue as even changing the battery had not stopped the battery light flashing on and off my dashboard... I hope it's just a bad fuse or worse case sceanrio an oil issue considering my alternator is located right under the oil feed it might be oil leaking on it so I will have to change both the alternator and check for a leak. I own a small car, the alternator will be a pain in the ass to dismantle, Christmas is in two days and we still haven't bough the food, there is no way I can check the alternator and receive a new one before Christmas. Yup I'm in some deep shit right now... Anyway Happy Christmas people!

[@lecobra418]

It was the alternator, I changed it a week ago (after two weeks of charging the battery every three trips) and it now runs like a clock!

[@tjtewshews5531]

At least you had the sense to buy a battery to get home. My dumb ass had it towed for $125 to my house knowing i have a 3 year old battery that needs to be replaced anyway.

[@vincesanzari1709]

If you have a bad alternator but good battery, once you start your car , disconnect positive post on battery and the car will stop. 👍

[@yoihavoc8185]

@@7ThrillFishing yea

[@mrau92me]

That's not a good practice on today's cars because of the sensitive electronic components and sensors. The battery acts as a voltage stabilizer when it's in the loop.

[@savannahduncan3786]

Ah but what if my car don’t start.

[@vincesanzari1709]

@@savannahduncan3786 first you have to ensure your battery is fully charged to start your car. If your battery is over 5 years old and does not fully charge, it’s time for a new battery. Usually when you have an alternator issue you should have an error code on dashboard.

[@vincesanzari1709]

@@mrau92me it’s not good practice but it’s a quick test if your stranded and don’t have too tools at your disposal. Dealer replaced my alternator which I suspected after 11 years. Test was done 30 minutes after I had battery error code on dashboard. Battery was charged overnight and drove 15 minutes to dealer.

[@anchormanronburgandy]

Am I the only person who is missing the part about where the black probe is attached when you're testing the alternator? You go red to the alternator (b+) then is the black attached to the negative (ground) on your battery? At 4:34 you run your next test but still don't confirm where the black probe is, I'm still just assuming ground but can you confirm?

[@petep.2092]

Yes.

[@anchormanronburgandy]

Thanks!@@petep.2092

[@smurphyslaw2300]

Very logical video. Thanks

[@derrickhoward9156]

Thank you for your video. I used your advice and found that the positive wire to the alternator was not connected well at the battery.

[@mymusic3354]

Man....This video is awesome! You do an EXCELLENT job explaining and showing what to do....My truck had the battery light come on and go off a couple times one day while driving, and the truck's voltage gauge in the instrument cluster which had been showing that the battery was being charged, and would increase voltage with higher RPMs as usual.... Suddenly the battery light flashes a couple times and the gauge dropped to where it sits with a fully charged battery and no longer moved when raising RPMs....I made it home and parked it and have been contemplating what to do next....I'm curious though whether an alternator would be seeming to work fine then just totally quit....When I check at the battery posts it doesn't show anything, just the battery charge level itself, where it usually would show 14 when the engine was running, it was showing a full battery and the alternator charging but after driving it and the battery light flashing where it had been showing the battery being charged now it just shows the battery's charge level but nothing else....I guess I'll check the charging situation you detailed here and see what I get....could there be a fuse that blew or something somewhere, I don't know, trying to narrow down the cause as with driving it just running off the battery I don't want to be left stranded somewhere....Thanks for the video, this gives me some more ideas to check out. It starts up and runs....But for how long it would drive...It probably wouldn't make it to an auto repair shop....Subscribed to your channel. Hoping I can find the cause of these symptoms and hopefully fix it without a trip to a mechanic (I am mechanically inclined to some degree and grew up watching auto repair shows on TV, even more often than I watched cartoons 🤣😂🤣 This was a weird problem though how it went from charging fine to battery light flashes on and off a couple times and voltage drop....The battery light hasn't stayed on or anything but but not getting a charge....Great video. Super helpful.

[@bv4u9876]

Video was precise and informative. Appreciated that you made a video that was easy to understand!

[@robertgalante4706]

Alternator video Was great. Can you help me with Power Steering pump ? When 07 Honda Accord starts up early a rattling noise coming from pump I t was low on fluid but added . But this bearing noise coming from pump making it slightly harder to steer the car..Bob Galante..Love A-1 Auto..

[@RyRch]

3:07 Should the engine be still running at this point for this test?

[@jerryking8877]

You should test the total resistance of your electrical system's ground system by placing the meter's two leads anywhere between the negative battery terminal, the #8 awg copper conductor attached to it, the alternator's metal housing and/or the vehicle's chassis and also the engine's hoist bracket. You should read less than 1 ohm when measuring between any of these mentioned ground points when utilizing the lowest resistance setting/ ohms setting on your meter. Anything above that is a problem and most often if the reading is not almost zero, then it tends to measure a significant amount of resistance due to poorly maintained ground lugs, rust covered terminal points, badly corroded or even painted metal surfaces that need to be perfectly prepped bare metal to metal bonding points. I've seen many vehicles that measure millions of ohms (Mega ohms) between the negative battery terminal and the chassis ground bonding lug only 1 meter away. That's a huge issue that has to be corrected in order for the electrical charging system to be able to provide that very necessary service to the battery.

[@petep.2092]

Usually the BAT- is grounded to the engine block to provide the least ground return resistance for both the starter and the alternator. Ground resistance of more than a few milliohms will result in very poor starter performance; with a megaohm of resistance the starter will be inoperative, you may as well not have a battery installed. With one ohm resistance, E= I x R and a 10 amp current draw will drop 10V across that resistance, leaving 2V across the starter, which is not even enough to hold the starter solenoid closed and it will open, then close again, producing that clacking noise.

[@stemo342]

Good video! I use both. Battery load tester and volt meter.

[@tanoktenahua1665]

Thank you for this video, I have a 04 Jeep grand cherokee 4.0l that i just replace the alternator and the battery. It gave me a check gauge light on and the battery level was just above 9v. I am now charging the battery it's at 11.3v and I will be check all that you said. Thanks again.

[@rodrigomillan8483]

Thanks for the show, I learn a few things , but I am confused becasue I though 12.39 is wen your batter is dead or close to dead, my jeep starts also below 12.39 volts.

[@Joseph-eh4rs]

No, that's when below 12v like 11.5v

[@radishpea6615]

3:31 With engine running, if no more then "12/13 volts", what part of the alternator is faulty? Voltage regulator, rectifier, or armature/windings? May be a bit too soon to buy a new alternator. Further testing is required.

[@judylee1860]

It would be nice to know if the negative on the voltmeter stays on the battery when taking the alternator reading.

[@comodice905]

Dawg genius when this hits the fleet macdaddy boogie

[@marioabello7137]

Simple and direct explanation. TNX

[@Mrgulaman]

thanks for this helpful video. Helped me figure out my alternator was bad. Now try this on an EV car lol

[@fcolon1976]

Awesome video thank you for the tutorial 👍

[@cyberbid]

Thank you for the upload. I will try some of these out on my wife’s Honda crv. It has a starting problem and we are tired of it. Even the mechanics have more or less given up on it

[@Pgan803]

TQ Sir, this is very good, very useful

[@Niqu33n]

I have a 2005 nissan altima (LOL) annd i replaced the battery twice, recharged it to be sure and also replaced the alternator. I drove for 10 mins and it just stalled (It wouldnt accelerate when i press the gas pedal) but the lights were still on?? So what could it be because its about to get trashed lol

[@Niqu33n]

I really need help.. 😮‍💨 So is it the alternator?? Like what is it

[@promptengineered]

It's a Nissan altima.

[@Niqu33n]

@@promptengineered no actually It just needed love ad care. Shes all fixed up now and driving and speeding like a Nissan Ultima 🙃

[@promptengineered]

@@Niqu33n hahahah good to hear. Baby that car like it's the old ass queen of England. Maybe then it'll last a good long time. Cheers!

[@peterjohndesmond369]

very well explained thank you

[@patriciatilley7475]

This has been very helpful

[@JamesSaintRave]

Complete and detailed--thanks!😀

[@junbug779]

Great vid man thanks for all the helpful info keep up the great content

[@thesteveshowfoodfestroadtest]

Killer vid! Much appreciated!

[@SalvadorHernandez-to2gq]

I'll tell you of an easier way of testing the alternator. With the engine running disconnect either battery terminal (negative or positive) if the engine stays running the alternator is good, if the engine stops the alternator is not putting out a charge. 🤷

[@tedlahm5740]

To explain Voltage Drop, you need to go into some detail. Kirchhoff’s voltage rule for series circuits.

[@tonyreyes9969]

I normally use a Volt/Ampere Meter tester to check the charging output of a vehicle ( with and without load ).

[@kitchens2clean]

Definitely going to be gettjng a voltmeter to do this thank you

[@tkjazzer]

When touching lead on back of alternator with red lead, what is black lead touching?

[@nebulousJames12345]

negative battery terminal

[@jerzywilk7788]

Very informative

[@jw112965]

Used this today. Thank you

[@rjccattley]

Hi when you check back alternators is it AC or DC On the meter

[@mfsmfs63]

Direct Current

[@chanhducphung2826]

Thank so much for your great details video

[@_SPECTER_]

Great job explaining

[@allanturton1637]

Thank you for the video!

[@glensmall9194]

Great video. Thank you. Now to test the alternator on my 1976 Series 3 Land Rover. Best wishes from New Zealand.

[@apuz13]

Awesome video. Can I attach the multimeter while the car is running to test the alternator?

[@petep.2092]

Yes, be careful that long wires, clothing, etc. don't get caught in rotating parts, likely serious injury or death. If possible use clip type probes instead of bayonet, and make hookup and route wires and ensure meter is stable before starting engine and don't reach for meter or probes while engine is running.

[@bfglife4164]

Another good test disconnect the live the alternator should keep the car running without it if it dies there lays the issue

[@roybatty2030]

Super video, thanks.

[@hmroa3056]

Helpful, thank you, but I was not sure about which tests required the engine to be running or not.

[@petep.2092]

The battery voltage jump test (12V off -> 13.2V-14.6V running) and the voltage drop test (0V) between ALT+ and BAT+