How to test your vehicles alternator using a multimeter.

[MrNedgoak]

Replaced the battery and Alternator( with voltage reg) and my battery is loosing charge somehow. Watched your video and purchased a multimeter and the readings are as follows:1. car off battery reading is 12.2. 2. After it is started the number slowly(10sec) climbs to 13.8-14 area. 3.Then with the car running and the heater blower on high and the headlights on the reading goes down to the 10.5 area but does increase when the motor is rev'ed up to 1500 rpms. My belts are tight. I am stumped

[Johnnysshop]

@MrNedgoak Sounds like either the alternator is not powerful enough or the new one is bad.. Not likely but possible.

[50MOLE]

SIMPLE THANKS ONLY ISSUE I HAVE IS DO I NEED TO SWITCH METER TO THAT 20...NUMBER? IS THAT DC..OR AC?

[Johnnysshop]

@50MOLE 20, DC

[DrD0000M]

eBay has multi-meters for $3.60 delivered folks. Yes, they work.

[Marcaveli7]

Cool, thanks! Didn't know you could do that

[Johnnysshop]

@Marcaveli7 Thanks for watching!

[doctorxombie]

Thanx for the video.

No instructions came with the meter and I didn't want to blow something accidentally.

Very helpful video.

[Johnnysshop]

@doctorxombie Thanks, I appreciate the positive feedback!

[da1stegr]

Great info...Question: I have a Optima battery, and when I tested it with an ohm-meter it read 12.3 not on the car, it was charged a month ago and it was ok. Now it's at 12.3 . What should I do ?

[Johnnysshop]

@da1stegr it's 12.3 with the car running?

[da1stegr]

@Johnnysshop no, it's outside of the car .I haven't used it for anything in months. my tranny went out a few months ago so now I'm just gonna re do the whole car (paint,restoration ect..), but I don't want my battery to die scince it's in mint condition (case wise). I heard it might be deeply discharged is that true? what tips can you give me I'd greatly be appreciated. tnx

[Johnnysshop]

@da1stegr I guess it could do that but I've never had that happen. I would just charge it once a month or so. Or check it at least. 12.3 is fine.

[da1stegr]

@Johnnysshop well when I took it to Auto crap (auto zone) to have it charged they said it take 37 min well it got late so I went the very next day to pick it up and it was still in the charger. And i was like wtf you know. then they said it needs to be charged. I said it tought you guys already did that that. so he tries 2 charge it AGAIN and this time i wasn't leaving it. he came back not even 1 min later and said it was dead. I was like WoW . Wtf yesterday it was ok and now it's dead? hmmm??

[Johnnysshop]

@da1stegr Yeah, odd. Good ole' Autozone!

[carlosm2010]

Thanks you, now I do not have to pay the mechanic to test my alternator!!!!

[Johnnysshop]

@carlosm2010 Glad I could help!

[rotcataergeht]

i start my car n i got 13.55 is that a good reading?

[Johnnysshop]

@rotcataergeht Yeah, it's fine.

[absgt]

Thanks, really helpful video.

[Johnnysshop]

@absgt Thanks for watching!

[superbeast0934]

my car doesn't start.....

[Johnnysshop]

@superbeast0934 Does it try to turn over?

[sixstringthing1]

Very well done video. Clear and to the point. Thanks.

[Johnnysshop]

@sixstringthing1 Thanks!

[StevenChandlerArtist]

You know those two little plugs on the multimeter, I cannot find anywhere that shows you what plug to stick in what. I know this is stupid, just never used one and bought one to test my alternator, stuck the black one in the COM and the red one in the DC Unfused and the multimeter started getting hot as hell, did it the other way and it worked, it just would be nice to know what the hell I did-thanks

[Johnnysshop]

@StevenChandlerArtist I hear ya, I did that a long time ago with a Craftsman I had. Blew it up though..

[StevenChandlerArtist]

@Johnnysshop Thanks Johnny, I was able to figure it out with the help of some videos...the instructions for the thing stink, but it was a cheapy. I think I had a parasitic draw from a poorly installed radio the previous owner installed,Thanks again,SC

[MrNoe669]

mine shows 17.5 is that ok?



[Johnnysshop]

@MrNoe669 Sounds too high. Sounds like the voltage regulator is fried, which is in the alternator. Might be time to replace.

[MrNoe669]

whats next if it fails this test?

[Johnnysshop]

@MrNoe669 You'd have to replace the alternator.

[MrNoe669]

@Johnnysshop thanks it was fried i rebuild it at a shop

[jdm2envy]

hello, i want it to know if this test will work on 99 honda civic? i thnk i have a problem on my alternator because my dashboard light is dimming.

[Johnnysshop]

@jdm2envy Yep

[flipdZone]

I bought a new car battery because the old one kept draining after a couple days. This new one I have is now doing the same thing after my car is not use for 2 days. When i tested it the voltage is just below 12V (11.4...). When I do the alternator test it charges up to 14+V..

What could be causing the battery to drain?

Thanks

[Johnnysshop]

@flipdZone Could be anything. I would check for anything that could be left on. Believe it or not a common cause is a trunk light or glove box light staying on.

[Johnnysshop]

Oh yeah, if it's draining the batts for sure.

[heymrfoster]

I jus don't think that alternator is du n its job its draining my batteries not charging em

[heymrfoster]

I got a 99 suburban with a 200 amp alternator an 2 red top optima batteries plus I dun the big 3 upgrade as well, I shudnt have n e problems shud I?

[Johnnysshop]

@heymrfoster Sounds like you have more than enough!

[heymrfoster]

Ok wut if I unhook the battery while the car is runnin an the car dies

[Johnnysshop]

@heymrfoster That trick holds true on older cars but not necessarily on the newer ones. A lot more electronics in them now.

[heymrfoster]

what if the voltage remains the same until u hit the gas petal then it jumps up 2 14.5?

[Johnnysshop]

@heymrfoster That's fine

[resist4resist]

Thank you for these videos. I really enjoyed watching your videos, very clear, comprehensive and simple. May I know the brand and the model number of your multimeter? Thanks a lot!!

[Johnnysshop]

@resist4resist Thanks, I appreciate the feedback! It's an IDeal Test Pro part#61-361

[resist4resist]

@Johnnysshop Thank you very much for the information on multimeter. I really admire people like you who like to spread knowledge and skills through brilliantly shot and edited videos so that people at large can benefit. Thank you so much!

[2k7gixxxer]

awesome video... thanks for your help

[Johnnysshop]

@2k7gixxxer Thanks!

[Captor96]

thanks johnny i like the video very helpful .there is also the possibility that there could also be a breakage in the line between the batterie and the alternator or a bad connection caused by rust . well i live in canada where it's cold and things get rusty fast if you don't use the proper lubricant where the connections meet.

[Johnnysshop]

@Captor96 It is possible, just use the multimeter directly on the leads.

[JetRanger0007]

Except for us Dummies you forgot to show & tell us where to hook the leads up to at the alternator before testing,,, maybe next time !

[Johnnysshop]

@kelkenb8 Thanks!

[CEEPMDEE]

nice video

[Johnnysshop]

@CEEPMDEE Thanks!

[GixxerJay13]

All videos are quick and to the point, good quality and easy to understand!

Thanks!!!!

[Johnnysshop]

@GixxerJay13 Thanks!

[billyjames1085]

Thank you for this simple easy to understand and accomplish test. I knew it had to be simple to determine if the alternator on my car is the problem with no starting.

[Johnnysshop]

@billyjames1085 Thanks for watching, glad I could help!

[4EVERMYSERENITY]

Hi I am trying to learn how to use my meter, I bought it from Napa and I don't know how to set it and how to test my marine battery, it's a digital meter with multi functions, could you plese help me, thanks

[Johnnysshop]

@4EVERMYSERENITY Have a link or pictures to post?

[zccolby]

some alternators run lower, like around 13.5 v but thats not typically bad to say.. anyways, good video. im going to get an EXTECH multimeter for christmas i think. should prove handy when doing my car audio build

[BLAZEPSI]

You always make it the right and easy way for PPL like me to understand...noobs like me...THANKS...

[Johnnysshop]

@BLAZEPSI Thanks, I try my best!

[traxxa5]

very easy to follow video thanks

[Johnnysshop]

@traxxa5 Thanks, I appreciate the feedback.

[en4cer450]

I tested my alternator with my battery fully charged. The alternator maxes out at about 13.2V with the engine running along with the headlights, A/C @ full power, and the domelight illuminated. Revving the engine has no effect on the reading. Would this indicate a bad alt., regulator, diodes, or something else? Also getting a faint flicker at the domelight.

[Johnnysshop]

@en4cer450 Typically with a bad alternator turning on those you would notice a huge change with all you mentioned. What makes you think it's bad aside from the reading? Check it at the alternator as well (instead of the battery).

[en4cer450]

@Johnnysshop According to the video, if it's not cranking 14-14.5, it may be going bad; mine isn't even reaching 14. Also, with the light flicker at my domelight, and courtesy lights, I thought it may be my volt. regulator.

[frankfordbully]

@en4cer450 flicker in the dome light is isolated to that circuit..loose connection..bulb maybe on it's way out..it's normal to have a small drop with all the "loads" turned on..13.2-14.5 or so is normal..I perfer to use and amp clamp to see how much current is being pulled from the altenator VS the battery..

[N4tti1ntampa]

Awesome video!!!

[Johnnysshop]

@N4tti1ntampa Thanks!

[sgntelias]

if it's an alternator, why is it not alternating current, why is it DC?

[shehjadhafeji]

as as i have learned in class its becouse the bettary is a DC device

[Johnnysshop]

@sgntelias It runs off a battery which is DC...

[frankfordbully]

@sgntelias produces 3phase A.C..uses a rectifier to convert it to D.C.

[Oozingmachismo24]

Actually a bad alternator can also go up(overcharge) in voltage.Its should be between 13.5 to14.5(15 on japanese cars) volts. Any higher and its overcharging. An alternator can overcharge due to a bad voltage regulator and create a major draw and heat on the circuit resulting in battery discharge due to electrolyte evaporating

[Johnnysshop]

@Oozingmachismo24 True, I think I have another vid explaining bad regs as well.

[underpantswedgy]

@Oozingmachismo24 so what would be the solution it the alternator is overcharging? would one need to replace the alternator, or replace a part inside?

[frankfordbully]

@underpantswedgy most cars the voltage regulator is in the altenator and is replaced as a unit..i know my first car 86 mercury sable it was external and could be replaced by it self

[Johnnysshop]

@enlopez2k9 Depends. Usually it is.

[Johnnysshop]

@enlopez2k9 I would check the ground on your alternator. Sounds like a wiring issue.

[jesusfreakster101]

Thank you kindly Bro!!! I've always wanted a meter, and now with your teaching I feel confident on how to use it!!!

God Bless

[Johnnysshop]

@jesusfreakster101 Thanks, I appreciate the positive feedback!

[dvreaux]

Thanks for the lesson, bud. I just replaced my battery and am curious if my alternator is bad. I'll check it soon :)

[Johnnysshop]

@dvreaux Thanks for watching and the comments!

[sini8080]

Another great vid!

[Johnnysshop]

@sini8080 Thanks!

[tbmst2]

what brand or name is your multimeter

[Johnnysshop]

@tbmst2 Ideal. Fluke is the best but you are gonna pay for it! 

[TheDebecks]

THANK YOU

[Johnnysshop]

@TheDebecks Thanks for watching!

[Liamautomechanic]

VERY GOOD JOHN.

[Johnnysshop]

@Liamautomechanic Thanks!

[Raven3161]

It was very informative, thank you and keep up the good work.

[Johnnysshop]

@Raven3161 Thanks, I appreciate it!

[robakagt]

Thanks ALOT! Got a mutimeter and to read the manual you needed a degree in electronics.  Thanks to your videos I now know how to use it!

[Johnnysshop]

@robakagt LOL.. Yeah, the manuals aren't very well written usually. Glad I could help!

[cutecowboy123ca]

how about a Motorcycle? in car you put it on 20 DC as I heared if I am right?!

[Johnnysshop]

@cutecowboy123ca Motorcycle would be the same way and settings, just 6 volt system

[dankbobby]

I think I may have blown a fuse in my motorcycle, can I test for that as well? Thanks

[Johnnysshop]

@dankbobby Yes, just have to set it on continuity.

[racethisescort89]

ok well figured it out my battery terminal was crap so replaced it the alternator still intermittenly squeeks when my subwoofer pounds its only a 200W amp

[Johnnysshop]

A lot of factors actually. 200w isn't bad but gauge of power wire, ground, location of the ground, etc can play a part in it. What kind of car? What year?

[racethisescort89]

i have a question my battery wont hold a charge BUT the alternator squeeks everytime my subwoofer pounds., i know my battery need to be re filled with water but why would my alternator squeek only everytime the subwoofer pumps if the stereo is off its silent.

[Johnnysshop]

Probably need a larger alternator. Larger system put a huge drain on stock alternators.

[ils360]

COOL video i like it =D 5*****

[Johnnysshop]

Thanks!