Bad Battery Or Bad Alternator? How To Tell The Difference

[@NR-vw2rd]

Paul, thank you for educating the many of us who don’t know much about automobiles and didn’t really grow up with one. Everyone assumes kids grow up with a Dad who teaches them about cars. Great video.

[@johna5039]

Don’t do this. It is horrible advice, especially on modern vehicles unless your intention is to destroy the computer lol.

[@DavidRodriguez-hg6kq]

@@johna5039 I did this on a 2012 Nissan Murano with no damage.

[@chima411]

You are a Godsent with this information. No ceremonies....or blabbing. Straight to the point. Apparently you did this to ACTUALLY help people, and not for like and views (even though those are much desired). Anyway, thank You Sir. This was very timely.

[@incognito-yj4gu]

Multimeter is the best method. I would add to turn on all electrical devices on the vehicle... lights, AC, rear defogger, radio, wipers. With the engine idling the voltage on the battery should remain above 13 volts. Anything less would indicate a weak or defective alternator. A good indicator of a bad battery is the vehicle won't start after sitting overnight (assuming nothing was left on such as headlights or interior lights).

[@crystalo3550]

Thanks I am trying to figure out my problem in morning or anytime it's sitting and doesn't have to be very long sit but it's hesitating to start like sounds like it's going to and it eventually does but seems to be getting longer in the process so before it use to start up fine but now it seems like it is taking longer each time I go to start it today I didn't think it was going to it sounds like I'm about to drain the battery and nothing is left on I know my filter is shot no good could that cause it to not get good air flow so kinda like plugged causing it to lag or no

[@markk3652]

Air filter has nothing to do with the battery. It may contribute to the engine cranking longer than it normally would because it is getting restricted air flow. There is either a bad cell in the battery, or it has simply lived out its lifespan. There could be corrosion on connections causing high resistance and low current flow. There could be parasitic drain overnight from a short in the wiring, or an accessory. There could be a defective module in the car causing the drain. As you can see, there are numerous reasons that may be at the core of your trouble, so start with the basics first. Get the battery and charging system checked at an auto parts store or a mechanic.

[@Viquor]

What if it sits high 14v to 15.5v?

[@MeloneKidd]

So I disconnect my battery via a metal switch you connect and or disconnect from the red wire I believe. I disconnect my battery overnight or when I'm working and it used to keep the battery from draining. Now it drains either way and won't start. I'm assuming it's a bad battery. What's your opinion?

[@indyguy3400]

@@incognito-yj4gu you know it can put out 14v and still very little amperage right, amps matter. Moden alternators can put out just over 15v and that acceptable if you'd read the electrical section

[@xonx209]

The rising voltage test is probably the easiest with nothing to disconnect.

[@farrellwatson1428]

You shouldn’t remove the positive cable while the engine is running in modern vehicle. You run the risk of damaging the computers and modules that cars these days have.

[@issycard2398]

This comment should be highlighted

[@missionpawsible954]

Thank You! This Guy is an idiot and could be costing people thousands. This is THE worst DYI video ever!

[@obedhyppolite275]

Not the battery powering the components but the alternator does, when alternator failing the battery 🔋 is here to backup the computers until it drains out

[@tronixq9279]

Correct

[@mykecamp8275]

Not if you have common sense

[@stevetrivago]

Wow… no mechanic I’ve ever dealt with would offer this information… Thank you

[@JohnSmith-uy7sv]

Because it's all about money and not helping someone. That would take away their business. 😍

[@charlesbarkwell7693]

Because it's incorrect information. 98 % of it.

[@NN-sp9tu]

@@charlesbarkwell7693 Which part

[@SH-jp7in]

Needed this video today. Thanks so much. Issue was a bad battery. Much cheaper fix than the suspected alternator or starter.

[@jackaroo5]

Disconnection positive lead can damage electronics in your car. The Alternator output give out max amp when you disconnect the battery. It'll work with much older cars though.

[@cg_frm_da_6ix427]

Older cars like 1997?

[@lynskyrd]

you're not leaving the positive lead disconnected long enough for 'damage' to occur. This is a brief test.

[@wilsonbaeza4384]

What year and below is considered an old car???

[@dustbat]

I have also found if you are having odd or strange electrical problems and shops are obviously guessing, bite the bullet and try a new battery. Seen it solve stuff several times. Great video and reminds me what I already knew but time has stolen. Thanks.🦇

[@andrewdanvers308]

Yup, I've seen newer cars develop all kinds of funky electrical issue with a marginal battery while having a good running alternator. When swapped with a new battery, the issues go away immediately.

[@tonyjordan1320]

My sister's car was doing all kind of funky electrical issues-I called the tow service I used and he told me to replace the battery first and see if that didn't clear it up-Worked like a charm, this was a year ago...

[@robonymous4620]

Thank you so much for your kindness and generosity in putting out this simple, quick, and awesome video. Bad alternator for me (unfortunately) ... but great video, such a time saver! Thank you. 👍😊

[@papawd3991]

I have this situation with my 97 F-150, hence the reason I watched your video. The reason I liked and subscribed was due to your excellent communication, attitude, and exit greeting. Thank-you sir for the info and content without unnecessary language.

[@CryptoWolf1]

Me to 6 cylinder

[@jimmysapien9961]

Scotty Kilmer -Brother !

[@smjohn4640]

OMG... I wish I saw this video first. Thank you so much brother, God bless you. Trying to figure out what's going on with my pt cruiser and why the battery keeps draining. In researching over the last day I have watched many videos with some over 1hr long and have me looking at tools I need to get. This is the shortest yet fastest to the point and least complicated video I have seen on the topic.

[@proclaimliberty2000]

You need to watch my video Bad Battery? Bad Alternator? Or Parasitic Drain?

[@robertschleeter3300]

Thank you man. Straight to the point. Looked up 30 min worth of videos and you summed it up in 50 seconds. Battery light came on. Ran the car home from my shift for maybe 30-40 min and died on me right when i got back. Gonna try this method tomorrow. To determine whether its my battery or alternator.

[@dougburg3210]

it's the alternator

[@JulianAndreev]

It was definitely the alternator

[@robertschleeter3300]

@@JulianAndreev it was

[@tonyg-2jz82]

If a car shuts off while driving its 100% alternator. Good luck

[@glennnichols4220]

@@tonyg-2jz82 What happens if I can jump start my ISF from a dead battery, it runs when it is started doesn't die then I let it run for a bit, idle it up hook up a battery tester/charging system put a load on the tester/charging system it dies but the battery then reads weak on the system instead of being completely empty?

[@charliecubero2260]

Thanks for sharing your knowledge in a way everyone can understand.

[@carlbateman7733]

Handy and informative video, with the added bonus of a pretty decent Kermit the frog impersonation thrown in for good measure! Double winner!! 🐸😂

[@erastuserazade9785]

Sources , as Operator Manual of some cars , state that disconnecting battery while engine is running could potentially do damage to engine and electrical system. Volt check is the way to go ( humble reference input).

[@zacharymarron4112]

MYTH. Definitely not true. I’ve tried it. The only issue you’ll have is maybe have to reset the stations on you’re radio. 🤷🏼‍♂️

[@Bryan-hf7ll]

Fact most mechanics will fuck you car up more so you return

[@charlesbarkwell7693]

You're 110 % Correct. Partial Life Automotive background : Independent Auto Shops GM Dealership Southern California ( 90802 )

[@PrettyFly4aWi-Fi]

@@charlesbarkwell7693 nothing is 110% dummy.

[@Interesting70]

@@Bryan-hf7ll I had a cousing who was a diesel mechanic who told me their boss required this if the job didnt not cost enough,

[@auhsojffik9578]

Well, thanks to this video, I've narrowed it down. Thank you.

[@cocinandolamecanica]

“WITH ALL THE RESPECT “my dude but If it was that simple anybody could diagnose an alternator o electrical systems or when you connect the scanner to read codes and then change the parts according the codes 🤷🏻‍♂️ Disconnecting the battery while the engine is running could cause the electricity supplied by the alternator to go beyond the range deemed safe for the ECU, potentially frying the ECU. Again, should this happen, the vehicle will die, leaving you stranded. BUT IF YOU ARE LUCKY YOU COULD DIAGNOSE THIS WAY BUT “I STRONGLY NOT RECOMMEND “ This is my humble opinion as I have been repairing cars for over 20 years. Best regards!

[@wohoman2005]

Thanks for the old school technology. This is how we learned back in the 80s how to determine which was good and which was bad without a meter, thanks for refreshing my memory.🎉

[@montanapapakachallah6589]

Thanks. Im pretty sure my alternator went out last night. I knew about this trick but couldn’t remember which terminal you remove or if dying or keeping running meant alternator. Your video cleared it up. So, now I’m gonna go find out!

[@victoriamitchell6240]

Did you ever try the test. I'm VERY interested how it turned out as I'm having this issue as well. I have no experience in working on vehicles but this seems like a test I can do. I'm nervous though. Also, I've found another video that says to disconnect the negative cable so I'm confused now.

[@charlesbarkwell7693]

@@victoriamitchell6240 You should be confused , and I Ain't talking about whether to disconnect the Positive or Negative Battery Cable. I Graduated High School 1972. This is " Old School " Automotive Charging System Testing. This Test shouldn't be implemented on ANY vehicle that has Computers. If your vehicle can display " Check Engine " Light or " Service Engine Soon " Light - Run as fast as you can from this advice. First , call a Dealership Parts Department : - Give them your VIN # & ask them for the price of an Alternator and the price of the Main Computer. If you have " 3 " New 2022 Ford Mustangs in your Front Yard , 2 of them may start back up & " 1" car may Never Start.....What do you think the Customer is gonna do to ya. This kind of advice is still being given by " some " people whom has never had any Automotive Updated College exposure, ( even though their personalities are unbeatable ) Automotive background 35 - 45 % of my Life : GM Dealership Independent Automotive Shops Southern California ( 90802 )

[@victoriamitchell6240]

@@charlesbarkwell7693 thank you sir! 😊

[@charlesbarkwell7693]

@@victoriamitchell6240 3's and 8's and all of those other good numbers to ya. Vietnam Era Veteran ( 1973 - 1976 ) Honorable Discharge

[@JR-fp9rt]

Hey, Red Forman, you can fry a computer by arcing the positive cable. You want to disconnect the negative cable.

[@germancastillo8478]

0:40 Don't Do That With Moderns Cars Or You May Ruin The Computer System, As Your On Risk!

[@jaywholoveseveryone1721]

what do you mean modern? what year cars starts the modern era or is that for all cars with computer technology? thanks 💖

[@JohnSmith-uy7sv]

@@jaywholoveseveryone1721 😁 Maybe he lives in Cuba and the newest vehicles are in the 60's. If we change to socialism, that will be us one day.

[@quietcool4884]

Not true.

[@germancastillo8478]

@@JohnSmith-uy7sv nope, I live in the US, where there is alot of people like yourself ,thinking that the moon is made of cheese!!! Moron!!!

[@JohnSmith-uy7sv]

@@germancastillo8478 Yes, moron's who voted for Biden and Harris and Obama 3.0 and Hillary Clinton and George Soros and Pelosi and schumer. All morons.

[@johnjkizer6399]

Good bless you brother, Glory to our Loving God for His Mercy and Grace.

[@davidyj9013]

Removing +cable is one good check for alt working or not. Another way is an induction ammeter placed over output wire of alt. This will tell you amperage output but not voltage. With voltmeter on battery terminals, turn all accessories on to see if alternator keeps up with the load. If not, either alt or regulator. If so, battery needs to be fully charged, then load tested before being condemned.

[@Dhi-fe5eu]

Great video. Makes things a lot easier to diagnose.

[@spondyful]

Please be very careful about doing this because it may severely damage your electronics in your car. The logic is sound except there's a major problem. Battery acts a large capacity that buffers levels out the possible electrical spikes that alternator sometime generates whether it being a normal functioning or faulty alternator. Without the protection of a connected battery, the electrical spike will enter all the electronics of your car. The result may be nothing, if you're lucky, to catastrophic electrical shorts of all you electronics that may include your engine management system, lights, a/c, audio. power windows. Please read up on articles about this electrical spike before attempting this -- doing this may costs you thousands of dollars.

[@vonshango6311]

why is it not the same as a computer crash due to memory to prevent it?

[@charlesbarkwell7693]

You are 110 % Right !!

[@smokey6203]

This is a great video for a girl like me that doesn't know much about cars

[@proclaimliberty2000]

Lisa 620 you should seriously consider buying a craftsman digital multi meter like the one shown in this video. You could probably pick one up cheap on eBay for less than $20. They are easy to use and will provide you with invaluable information. I am on the treadmill right now but I’ll send you another helpful video today pertaining to digital multi meters and basic car maintenance.

[@proclaimliberty2000]

kzbin.info/www/bejne/qJS5ipl7bLKEoqs kzbin.info/www/bejne/rX7OlayNhMmqa8U

[@jayr7081]

Was a great video for me and I’m not a girl lol

[@shaunlastname391]

It's also a good video for midgets who don't know much about cars

[@youtubingbabs]

@@shaunlastname391 it's because girls get told to leave the garage growing up. Some dads talk to sons about cars bit not their daughters. Mechanics dumb stuff down to women... All this adds up to us feeling like knowing about cars is untouchable and magical. Lol. So it's normal for females to walk on eggshells regarding car shit. KZbin is life changing and empowering. Yay!

[@serg_gonsz]

Needed this reminder soo long since I had a bad alternator THANK YOU!

[@boomerang6130]

Love this guy. Simple, easy, and straight to the point. Brilliant! Love this guy--Thanks for creating and sharing this video . 👍 So helpful! PS - It was my battery btw. My alternator is good. 💲😁💲

[@taylernguyen3064]

wa

[@jimmysapien9961]

Scotty Kilmer’s Brother 👍🏻 Rev - your engines !!!!!

[@fordoverholden]

Yea helpful with the 80s cars. Wouldn't be doing that late 90s into the 2000s. Multimeter is the safest way.

[@rayburton4867]

Short and sweet! Great video!

[@JohnSmith-uy7sv]

I wasn't going to watch this, but when I saw the cross and what it said, I figured, what the hey. I always do mine with the volt meter and ran into a stranded motorist the other day and they said the car died while driving it and the battery was dead. I told them they probably needed a new alternator as it will keep your car running. Thanks for this video and reassurance of who the bad boy is. Now I don't need to carry a meter with me in my motorcycle to help someone. See you at home. 😍

[@renegadealpha95]

Simple. The other videos go on for 15 minutes. Thank you so much! Saved me a panic.

[@josephdavis4201]

After this, then you can find out which module you fried when you disconnected the battery. Cars are fun.

[@ACommenterOnYouTube]

You pull the battery cable and NO current flows, the entire circuit is dead. Nothing gets damaged

[@josephdavis4201]

@user-pv3qh8mo4n WRONG!! Don't try to school people if you don't know what you're talking about.

[@ACommenterOnYouTube]

@@josephdavis4201 You just GOT school'd 🤣

[@SportsMusicCars]

Test the battery when the car is off, remembering the reading. Then start the car, and compare the reading. The reading should go up with the car on as the alternator charges the battery. If the number is lower with the car on, the alternator is not charging the battery properly, if at all.

[@Sissy1212]

What if the car wont start ?

[@SportsMusicCars]

@@Sissy1212 might be a bad battery relay or starter? if there are at least some clicks, that would mean the battery is at least sending some power. if you're a novice Id take it to a mechanic or you will waste lots of time

[@Sissy1212]

@@SportsMusicCars the battery is new .. The car loss power while driving. We replaced the starter but it won't turn over still just clicks once . I can put the key n and turn it on and lights and stuff come on but won't start

[@SportsMusicCars]

@@Sissy1212 alternator

[@Sissy1212]

@@SportsMusicCars thanks I'll try n get that checked ♥

[@missionpawsible954]

SIMPLE descripes this SIMPLETON! NEVER remove the battery cable on a running engine! That was used as a diagnosis on generator operated engines, NOT altenators! Today's engines are completely computer controlled with sensors that are VOLTAGE sensitive! This IDIOT could cost you thousands in repair!

[@colvinator1611]

Excellent video! May I point out that a couple of years ago I had a problem with battery charging. It turned out to be the thin ( excitation ) wire that goes to the alternator from the ignition cct. was broken in the harness near the alternator. Best regards, Colin, UK.

[@babygamer405]

Not everyone has a volt meter laying around especially if you are not at home when the car died. Great video. Thanks a million!

[@greghayes9118]

In this day and age, it pays to learn a few basics and invest in some equipment, or pay the other way, road side mechanics call out fee then pray that they are being honest.

[@stephendriscoll7549]

Keep one in Your car then!

[@xonx209]

Then look at a dome light or headlight. If it gets brighter when you increase engine RPM, then alternator is good.

[@rickladrido9660]

Worst advice ever! That is, unless you want voltage spikes to ruin half the circuitry in your vehicle.

[@Pinkielover]

never ever remove your cars positive terminal while your car is running , Especially if you have a newer vehicle

[@tellez4089]

Fr lol

[@quietcool4884]

Not true.

[@dbs555]

@@quietcool4884 wow, that's awesome you want to help destroy the ECU of people's cars and trucks.

[@quietcool4884]

@@dbs555 LMAO, YA OK BUD.

[@DaveKraft1]

This may apply only to older cars, but an owner of a repair shop once gave me a pre-test for even these ideas. He said, with the car off, turn on the radio. If it goes on, it's likely the alternator is the problem, since the radio (in older cars anyway) took so little power that failure to go on would be a clear sign of a bad battery. Then, proceed to these other plans.

[@937youngjay]

Makes sense thanks

[@josephdavis4201]

The headlights work even better.

[@stubaker1737]

A week battery could run a radio but not start a car Einstein

[@troyedwards8100]

​@@stubaker1737 What is a car Einstein? And since when did we measure battery strength with units of time. A week?

[@johnkubricki5750]

Great way to fry the diodes in the alternator. This worked years ago, but not on newer vehicles.

[@bobjohnson1587]

Yes, DON'T do this with a newer vehicle!

[@samdim3746]

@@bobjohnson1587 even new vehicles can do this, when alternator is running all the power in the vehicle comes from alternator and not from the battery, try to test the current of all the electrical components and read the current rating it's still the same as the alternator.

[@allensmith9312]

Of course it could be neither.. Possible starter motor problem, loose fan belt, or electrical leak whilst the vehicle is parked.. (Glove box light stuck on for example)

[@rondemeio5337]

This test does not work on a lot of newer cars because the newer cars need the batteries to fire the coil packs. So if you pull the positive terminal off a newer vehicle the car will die because the coil packs require a constant power source. The method he's teaching you is for more older cars. So don't run out and buy a new alternator just because your car died when you took the positive line off. There are a lot of people saying that you might fry the computer if you take the positive terminal off that is a very slim chance of that happening. The main reason why you don't take the positive terminal off and use it as a diagnostics is because modern cars rely on the battery for starting power and for constant drain AKA keeping the coil packs running keeping the computer on and keeping the electric fuel pump running. The alternator is triggered by the computer when the computer detects the battery voltage has dropped below a certain percentage. But because the alternator needs to be spinning in order to generate power when you cut power off from a coil pack the alternator is not a constant enough power to keep a coil pack running at the same time as everything else and the car will just flatline. I've been working on cars for 30 years. If you have a car from early 90s and older this method that he shows you will work. I repeat do not use the positive terminal as you're diagnostics for an alternator on a new car. You could possibly damage your car by doing what he's showing you, but most likely you will not damage your car but your car will stall because it needs the battery.

[@ibo1137]

Can i do this test on my 2015 Ford Fiesta 1.0 Ecoboost?

[@kevinwillard4835]

Do not do this with cars with ecms you will blow your ecm and pay bucs

[@natashacrum2422]

You are a God send. I've been trouble shooting and repairing my vehichle on my own. Videos like this make that possible.

[@loobwan3963]

Hi, many thanks for making this video, I didn't know until I come to this show, thanks for taking your time, bro. helps me.

[@ericeric6342]

Great info, simple, concise and to the point! Thx!!!

[@crsddabc5568]

DO NOT DO THIS WITH NEWER VEHICLES… you will ruin your computer.

[@youngpineapple999]

What years would be considered new

[@KickKickPush92]

@@youngpineapple999 hard to say, from brand to brand.

[@bigmike4720]

Any car with a computer don't do this

[@Yashiro-nene_dies]

I did this with a 98 Mitsubishi eclipse and fried my ECU.

[@e.l.4860]

Yeah, you're never supposed to remove the positive cable first, there's a high risk of blowing your electric system, negative cable should always be removed first.

[@davidd1395]

Didn’t know that trick with removing the + while running. Thanks!

[@forhisglory700]

Thank you for this video; and the assistance. Blessings in Christ.

[@darrenochoa2250]

I seen one video that the guy disconnected the negative battery terminal while the car was running and the car stopped running and he said that the alternator was bad.

[@CindyPage-n3m]

what if you do Not have a battery gauge? My car 🚨 s a 2002 Dodge Status 4 door I have to get a jump start every morning! I Needed an Ignition switch ,but have Not got it installed, but it is rigged up ,and. I I just put my key ,in the little black square ,from the steering wheel and it starts once charged! I just want to know ,why I have to get a quick boost ,to my cable .my battery is under my car but ,I used the neg and positive little cable on the top

[@chumdog90]

DO NOT disconnect the positive terminal while the engine is running!!! That would cause irreversible damage to the vehicle's computer system.

[@gamerepair2020]

My car had a randomly bad alternator. Sometimes the car will work for weeks or months, then I would go to the store, come out 20 minutes later and and the car wouldn't start. I think they said it was a bad diode draining the battery

[@dealman3312]

Thank you so much for this! Although I don’t think removing the positive terminal is a good think to do with a bmw

[@beebol2581]

Don’t do this. Your electronics might get fried. Just go and buy a multimeter, they’re cheap and do the job perfectly.

[@GrowthGuided]

Thank you so much my brother. Much appreciated for this video !

[@xHustleHaRdx]

Clear and simple. Thank you so much you are amazing. We all appreciate you

[@orboakin8074]

God bless you for this video, sir. I just stumbled on it randomly and it's helpful. I am relatively new to driving (almost one year at the wheel since I got my license) and videos like this really help me as a novice.

[@kellyclark7517]

Thank u kindly :) U said would work for “most cars”. Wat might that mean? God bless U2 brother✌🏼

[@joshrandall3632]

If you have a bad voltage regulator (built in to the alternator) the car will still run. If you replace your battery based on that, you'll end up replacing multiple batteries. Just use a multimeter to be safe.

[@JohnSmith-uy7sv]

So, if the regulator is bad, then you are going to get the same reading as a bad alternator once you get the battery charged. If the regulator is bad, then how will it get voltage to keep running. Impossible. As the old saying goes.... 6 of 1 and half a dozen of the other. 6 will always be 6. 😁 It won't run with a bad regulator either. No voltage is no voltage.

[@frankhoward7645]

@@JohnSmith-uy7sv If the regulator is bad, then you are going to get the same reading as a bad alternator because the regulator IS part of the alternator.

[@JohnSmith-uy7sv]

@@frankhoward7645 Exactly. and so the vehicle cannot run if the regulator or alternator is bad. 6 of 1, half dozen of the other. Bad is bad. 🤔

[@frankhoward7645]

@@JohnSmith-uy7sv Yes it can. With a bad alternator or regulator, the vehicle can still run on the battery alone until it dies.

[@JohnSmith-uy7sv]

@@frankhoward7645 Exactly the point we were talking about. It will die if the alternator or regulator is bad. It can't keep running if either is bad. That was my point.

[@chanvindersingh8573]

Excellent video. It's just an outstanding performance because you just came to the point & explained the true real methods of quick trick man. you are Great, thank a lot .

[@charlesbarkwell7693]

My Man gave just gave Millions of people 98 % incorrect Charging System Test procedures for Todays vehicles. Todays vehicles : Any vehicle with a Computer and with many other Computers on 1996 & Newer Onboard Diagnostic Generation 1 : 1980 - 1995 vehicles Onboard Diagnostic Generation 2 : 1996 to Present Year Partial background of Resume : GM Dealership Independent Automotive Shops Automotive College Courses Private Diagnostic Training Southern California ( 90802 )

[@god1246]

Unhooking the battery terminal while car is running is an old school technique that works on older cars but should not be done on newer ones

[@terrymah6139]

What is considered a newer car? I would like to try this on a 1994 Jeep Cherokee. Thinking it's old enough.

[@god1246]

@@terrymah6139 probably yea, I’ve done it to my 93 GMC Sierra a couple of times and it’s fine

[@nelsonmercado100]

im glad im ran to this video im having alternator problems.. thank you great explanation

[@44ten]

If you can get it running, take it to your local auto parts store. Most will test it for free.

[@marioavaughn]

I plan to use these tips soon .. Many thanks

[@alfredhughtayler2901]

I've changed a dozen alternators over the years. Like Paul says "Get a voltmeter". They are super-cheap and some even plug into the cigarette lighter. A healthy alternator will deliver 13.8 volts when the battery is fully charged, up to about 14.5 if the battery is low and the revs are high. Disconnecting the battery or other hanky panky while the car is running can generate a big fat voltage spike that could fry the computer in any car built after 1986. (Fried one in a Dodge Caravan once.)

[@edsherrod5216]

Great info to have. Never thought to take the positive battery cable off while the car is running to determine if it is the battery that is bad or the alternator that is bad.

[@pyrodon1910]

This is TERRIBLE advice. As long as your vehicle does not run on a carburetor DO NOT... I REPEAT DO NOTTTTT!!!!! follow this advice. You can and most likely will blow a ton of electronic systems in your car. This is because newer cars have tons of computers and electronics that are sensitive to voltage/ current spikes and by removing a battery terminal you are signaling a dead battery in the charge circuit which will result in the alternator ramping up it's charge output to maximum amperage (this is damaging to the alternator by the way) then when you reconnect the lead to the battery lug that massive current /voltage spike will be applied to all of the electronics and computers in your car blowing all of the most susceptible ones. This is a GREAT way to wind up with a $5,000+ repair bill on your hands. DO NOTTTTTTTT TRY THISSSSSS EVER!!!!!!! Additionally, if testing with a multimeter the voltage should NEVER go up. That is a clear indication that something is WRONG with the alternator's voltage regulator and you should have it repaired or replaced immediately. The alternator voltage should remain constant with all of the vehicle's accessory systems engaged (lights AC etc) it should not increase as the engine RPM increases either. Cheers.

[@MrDingDongPong]

Great stuff, appreciate people like you

[@dumbcat]

what about people who say that disconnecting the battery while your car is running can potentially fry your electronics and total the car?

[@germancastillo8478]

Dont do that

[@iam1smiley1]

Yes, you can cause power surges to your PCM/ECU computer by removing the cable like this. Your vehicle may be sensitive to this because it's relying on modules that are reporting the difference in millivolts....the difference within 1 volt ⚡

[@andygibson7250]

It is true electrical components can be damaged doing that I just have a 05 Chevy truck and the gauges went goofy from disconnected power I had to reset the needles on some gauges under the cover soi just broke it open. Definitely could be a gamble but that's my only bad experience and have done it with several newer vehicles.

[@ednavas7264]

Took out the positive from the battery while car was on and the engine didn't stop but when I accelerated the voltage didn't go up it marked 14.5 v so I still don't know if its the battery or alternator

[@TheIndianscout]

Bad battery

[@RipYgt]

What if it doesn’t start at all tho…

[@YellowVtec]

Check voltage to the battery

[@73richg]

Why does this car guy sound like that other car guy

[@DungNguyen-ru5kg]

Good one, since alternator generates electricity when car is running for everything, battery included, for recharging.

[@pedrotalavera3541]

This is ok for cars that don't have computers. But remember batteries explode...Completely wrong way to test a charging system. You better do a bit more research before you follow this person's advice if you don't want to damage your car and trow away money. Never disconnect a battery terminal while a vehicle is running. It can damage electronic components and worst, It can make a battery explode (Battery vapors can ignite when sparks are present)

[@8307c4]

Even on cars made before 1980 disconnecting the battery with the engine running can fry light bulbs and accessories (such as the radio) and burn fuses.

[@5.7_Angel]

At this point I need both replaced😂 tuff part is I don’t have money like that. I’m currently stuck in my driveway late to work😭💔

[@asadullah1640]

Great helpful, and informative video Thanks a bunch 🎉

[@GlobalWorldNews1]

Great video ,,, God bless you brother

[@John_doe627]

So everytime I don’t use my truck for 12 hours or so, it will need a jumpstart to start , when I don’t use jumpstart it won’t start or no lights turn , im not sure if it’s Alternator or battery , runs good on road doesn’t break down , just won’t start when it sits for a while needing a jumpstart

[@proclaimliberty2000]

@@John_doe627 As long as your alternator is putting out the proper voltage, my best guess is you have a bad diode in the alternator causing parasitic drain to the battery. Check my Playlist and you will find a video on how to check the diodes on the alternator.

[@waltercastillo5921]

Thank you brother and GOD bless you too !

[@BodhiNDaddy]

Beautiful and simple. Thanks man!

[@mike9733]

I would never do this!..as with some car you can destroy your alternator!..The reason why i know this is because i got a wiring diagram for my car and it stated! "Warning do NOT disconnect the battery while the car is running it will DESTROY the Alternator!"...so it might be OK on some cars it might not be OK for others!...check your car manual to see if this warning is stated!.....God bless!

[@crenge]

So putting the positive back on won’t cause electric shock or explosion?

[@mitchharrington625]

Hey mum can we have Scotty Kilmer? We have Scotty Kilmer at home The Scotty Kilmer at home:

[@hawkenman.549]

This is very old school that could be used on old cars to about the early 70s. NEVER, NEVER, NEVER do this on modern cars. You could short out the electronics in the computer. Some vehicles have more that one computer. Some devices run on other voltages other that 12v. Get a multimeter to check battery voltage and alternator output ONLY!!!

[@eddiem4722]

I was told from a mechanic not to do this to my 2008 car because it can damage the computer. He said it’s ok to do this on older cars but not newer cars.

[@wilsonbaeza4384]

What's an oler car

[@yacyou6257]

In today's new car you don't disconnect the positive cable off the battery while the car is running, it can back wash the current to your onboard computer and fry it completely. You only do that on very old cars. I have being a car mechanic for over 30 year and have all my certificates in electronics. You usually use a volt meter and check the voltage of the alternator before the positive connector of the battery. If your alternator is under the volt specification output than your alternator diodes all defective. You can check the amps from the alternator too with a amp meter and check the recommended amp specs, them you will really know that your alternator is good or not.

[@joogmanhd4878]

How old? mines a 05 Mazda. Tried this now it turns over but won’t stay started

[@dalokz]

Couldn't say it any better. ThIs outdated method will mess up a modern cars system (2006 and up) in no time. Use a digital meter to measure volts and amps.

[@Born2be76]

Exactly dont ever disconnect your cables on newer cars you'll be sad you did.

[@samzman4720]

What a great simplified explanation👍

[@ryshay]

Do I disconnect the positive or negative to check the alternator? Disconnect the negative battery cable before testing an alternator. Instead, use a voltmeter to perform a basic and safe test.

[@mattacuff2421]

NOT SO FAST! This only works for FAILED alternators and FAILED batteries. However! Both alternators AND batteries aren't GOOD or BAD...they can "GOING BAD"...In this case an alternator may be failing but still charging a bit. So perhaps its charging at 2000RPM but not at 1000RPM. ALSO, a battery may charge to 12V but wont hold that charge for as long as it should.

[@hanifelbey8463]

Excellent video short specific and completely correct info

[@MmpKendall]

Very helpful - thank you very much!

[@leoneljvalladares5402]

Thank you and God bless.

[@alphaomega5721]

Don't do this. Just don't. The alternator may suddenly see a low/no voltage scenario and send a voltage spike which may damage the diode pack, regulator or other components. Just don't.

[@edmundolanderos6085]

You are correct,thank you.

[@ecgodsmack86]

How do I know if my starter is going out? Great vid.

[@proclaimliberty2000]

kzbin.info/www/bejne/Z6imqa1teNuerdU kzbin.info/www/bejne/jHq6fKuIZtGiic0

[@quietcool4884]

Your engine doesn't turn over lol. You need to see what amps it draws. The usual problem with starters are the contacts in the solenoid that wear, not the starter itself. 30+ years auto electric rebuilder.

[@triogreymountain7284]

He be trynna steal scotty Kilmer introductions and accent. Unbelievable. Jk nah but thanks for the help.

[@metropulosjerrod]

Except you can have a weak alternator that'll keep the car running, but not charge enough to start

[@jimmycasas]

I accidently ran into your HELPFUL video Paul...I was telling my Dad about the recently replaced battery so I will try this exercise tomorrow in the daytime and let you know...Again, Thanks Paul.