How to Test an Alternator (fast and simple)

In this video I show the steps and procedures that are necessary to affectively test your alternator. It should be said before you do an alternator testing need to verify that your battery is good and fully charged. Since the battery is the main component of any cars electrical system it is imperative that the battery is good. I have seen countless misdiagnosis of an alternator when the problem is simply a battery. I hope you enjoy this video if you did please like and subscribe and let me know in the comments section how you diagnose an alternator in your own ways.
Battery Load Tester (works awesome to test alternator)
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Digital Multimeter Electrical Test Kit
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Professional Tool Kit with Heavy Duty Case
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Heavy Duty Black Industrial Nitrile Gloves
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How to test a battery video. • How to Test a Battery ...

[@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

[@aBieBi1]

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!🙏🏾

[@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

[@jaytee6513]

That fool may not be able to afford you, no compassion for the desperate.

[@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

[@sharonengebretson3164]

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

[@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!

[@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!!!

[@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.

[@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

[@TruthLifeFinder]

Very useful and simple to follow. Many thanks

[@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!

[@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

[@peggystaat2646]

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

[@jimbeauprez8235]

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

[@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 !

[@paradoxdea]

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

[@mommommy6135]

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

[@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.

[@marioabello7137]

Simple and direct explanation. TNX

[@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.

[@I.LikeCars]

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

[@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. 👍🏻😉🇺🇸🙏🏻✝️🇺🇸🙏🏻✝️🇺🇸👍🏻😉.

[@muhamadsunasrisamat7368]

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

[@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!!!

[@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!

[@1dd434]

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

[@bbulliard]

Super excellent world class video. Thank you so much

[@Louis-qi1gz]

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

[@Wesmancan]

Why would you watch this

[@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

[@LittleTimmy56789]

You’re the man. I just fixed my F350.

[@thetheDMT]

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

[@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 !!!

[@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

[@gonzalosanchez5073]

Nice,excellent and easy explanation. Thanks

[@joeygemini6390]

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

[@caseyostrander503]

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

[@logowatchman]

Very good video. Thanks!

[@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]

[@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

[@_SPECTER_]

Great job explaining

[@stemo342]

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

[@Staygoldfarms]

Awesome video. Thank you for sharing

[@johnremaly1906]

Thanks so much! You explained it very well..

[@JamesSaintRave]

Complete and detailed--thanks!😀

[@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

[@jerzywilk7788]

Very informative

[@johnbreak100golf]

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

[@jerrypatrick1047]

Thank you so much, Aaron....very informative and helpful!! U da man!!👍👊👊👊

[@LaTuyaa]

AWESOME Video, thank you so much!!!

[@junbug779]

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

[@mobileheavyequipmentrepair2981]

Very great breakdown!

[@terrysizemore9694]

Very well explained! Thank you..

[@glensmall9194]

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

[@nahhtoo7046]

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

[@WadeHufford]

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

[@mikedavis7312]

Thanks man I learned a couple of things very good info

[@majikmae2615]

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

[@jw112965]

Used this today. Thank you

[@albertbarrion1653]

Helpful video. Thanks.

[@mattsmith6828]

this is so useful! thank you so much.

[@rogwarrior]

Great video. Helped a lot.

[@TheMayatchico]

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

[@lindsaymitchell5984]

You just save me 400 bucks! Thanks man 😘

[@frzmck5900]

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

[@drdebrillos8909]

Thankyou excellent info

[@danielaramirez9615]

Such great video , thanks

[@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.

[@fcolon1976]

Awesome video thank you for the tutorial 👍

[@davidpotter7484]

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

[@chanhducphung2826]

Thank so much for your great details video

[@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).

[@peterjohndesmond369]

very well explained thank you

[@OGAC1]

Thanks for the info buddy

[@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.

[@kumaquattro]

Thanks, very helpful .

[@pinoyvienna]

Thanks. It was very helpful.

[@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.

[@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

[@allanturton1637]

Thank you for the video!

[@randyschmittou8708]

Very good video! Thanks for sharing!

[@peterharris5485]

Good info! Thanks.

[@patriciatilley7475]

This has been very helpful

[@thesteveshowfoodfestroadtest]

Killer vid! Much appreciated!

[@jsjs8818]

Great video, I'll have to purchase a voltmeter. I have a DieHard charger with a alternator tester. As the manual is gone, any direction on how to use it? Thank you.

[@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.

[@JohnPooley-te9ei]

Nice1..Aaron & thank u

[@zahariastoianovici8590]

Very helpful, thank you

[@roybatty2030]

Super video, thanks.

[@bvv1456]

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..

[@53yankee76]

I noticed you have the red lead on the negative post and the black on the positive. I’m accustom to always using the red for positive. Does it matter?

[@GrenPara]

Great video, Thanks for making it.

[@debrablack2759]

Thank you for your help. Love , Debra

[@elsiervoamistoso]

Thanks for sharing this info. 👍👍👍

[@michaelhadfield3755]

Very good video easy to follow 👍

[@johnspartan98]

A faulty PCM/ECM module can also cause a new alternator not to charge properly. Where do I find the fuse for the little wire you referred to? My vehicle is an 03 dodge ram 1500 with a 4.7.

[@marcuscheko2226]

should be in fuse box in engine compartmeant , its not a fuse that goes inside for somereason .....hope this helps , good luck

[@everythingisenergyenergyis3801]

Great info thank you

[@heyloheylo8361]

Ty fam helped more than u know

[@shiningwhitelight9710]

Very good video.

[@judylee1860]

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

[@CrazyCanuckFitness]

Very helpful. Thanks

[@vermasean]

Nice detailed video! Obligatory Liked and Sub’d! 👍▶️🔧

[@INTERNA9]

Best video. Thanx.