How to test an alternator the right way!
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- čas přidán 16. 07. 2024
- I will show you how to test an alternator the right way for voltage and amperage without using expensive amp meters. We will make a homeade shunt (amp clamp) to measure the alternator amperage output for under $5.
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I thought this was going to be another useless alternator voltage video, but turned out to be one of the most amazing videos I’ve seen! Never knew this could be done.
The "Shunt" here, I think, is actually a voltage divider.
First, about meters. Internal to the meter, between the "AMP" and "COM" connectections, is a shunt made from a calibrated size of copper. Although copper is considered a "conductor" there is still a resistance to copper that can be measured - although it will be in the milliohm or micro-ohm range (.001 to .000001 ohms). Suppose the internal shunt inside the meter for the amps function has a resistance of 1 milliohm. And now you hook the meter up to the battery while it is drawing 10 amps. Using Ohm's Law were E=IxR. That is, voltage = current x resistance. So, 10 amps x 0.001 ohms = 0.010 volts, or 10 millivolts. The meter is actually internally measuring 10 millivolts across the internal copper shunt (which is actually a precision 1 milliohm resistor) and the meter is actually displaying 10 millivolts... but since the human operator has selected the AMP function, the display scale is re-calibrated to be shown as amps so that the human operator does not have to keep using Ohm's Law to convert the meter reading.
The meter's internal shunt has a limit of safely handling 10 amps without damaging the very sensitive voltage measuring circuits. To measure current greater than 10 amps requires the use of an external shunt.
Think of his black wire, which has an overall resistance of about .002 milliohms (or 2,000 mico-ohms), as a long string of 2,000 one micro-ohm resisters connected end to end. At the end connected to the battery (at the first of our imaginary resistors) there is no voltage drop. At the 2,000th resistor at the other end there is about an 8 millivolt drop. So, along the length of the shunt, there is a gradient of voltage from 0 to 8 millivolts. By using the pin to probe through the insulation, he is finding the exact spot where the voltage drop is exactly 4.3 millivolts. He picked the spot where number of millivolts would equal the number of amps. He could have picked anywhere - but there would have been more math involved to convert the ratios. This way, we can just read the millivolts reading on the meter and know that it has a one-to-one ratio correspondence to the number of amps.
The theory for his shunt / voltage divider is actually covered in the first few days of DC Series Circuits. But, what Carolina Custom has done to turn a chunk of wire into a semi-calibrated meter multiplier is brilliantly clever!!
I have an amp clamp. It's nice because you don't need to disconnect anything but your shunt is a clever way to measure high amps. Good video.
You have opened up a lot of room with this video again thank you
I'm an Electrical Engineer and I approve of this video. Amazing DIY tool!!
Wht is he poking on the cable que made , setting at millivolts range ? and checking for 4.3
@@daaudiome I think a T shape needle available craft stores
@inventions ideas actually as an engineer my approval is needed for tons of stuff daily, but I was just showing some support for a great DIY tool. FWIW no one needs keyboard jocks telling ppl what to do lol.
@inventions ideas I think as a teacher for a few years during school I'm pretty covered for my "random keyboard warrior approval award" for giving back... 😂🤣😂🤣 what a joke
@inventions ideas lol I am American!
I learned something tonight. I worked as an electrician for years and did not know this, I always had a clamp meter at work but don't have one now that I'm retired. Very clever and now I'm going to make one so I can use it at home. Thank you for making this video :)
Very good video for the home mechanic.
Explaining and showing how to fabricate a highly usable measurement tool with simple means.
Even how to calibrate it - and that is pretty important - because you want to be sure that you have 1amp, when you are actually reading 1amp on the meter.
Great 💚
Good speaker teacher very knowldgable very good demo I've worked on car since 10 year agent 73 asof yeasterdaynever seen thing made so simple on 1_10 its a 15 thankyou
Just plain and simply AWESOME! Recently purchased high amp alternator. Also DC amp meter. Meter isnt showing anything to speak of. Ive got to insure the price of both articles was worth it. This homeboy shunt will do it. Thanks many times.
Wow, I have never seen something so ingenious!
Going to make one right now. Pricing amp clamps yesterday for a single use. Brilliant!
Yeah, I'm a 12V shop owner and I too like this video...well presented, sir.
You are awesome! I knew there was a way to do this I just couldn't figure it out myself. Thanks man
Well damn! That amp clamp is the one thing I wish I left my last job with 🤣
Now I don't feel so bad... I'm gonna make one of these tomorrow, because I think my Alternator is getting tired.
Thank you!
Subd
One of the most helpful car electrical tips I have ever seen. Thank You for the amazing post!
That was fun! I'd probably be more neurotic about insulating those clamps, myself, but, your point was clearly made ( no pun intended) THANK you ☺
I was thinking the same thing about insulation. I have insulated clamps similar to those. You can always throw some heat shrink around them.
Awesome Video! Thanks for the education. So cool to see this alternative method/how to measure amps indirectly
Wow, i know a enough to get me by but this is new knowledge to me. Being an entry level tech with limited funds, this seems like a really good technique to get a quick reading on a budget. thanks for the upload!
Nice. I can now test the actual charging current of our service vehicle to determine if my alternator is still working, without buying that expensive amp clamp. Thank you.
Thanks for the video, I'm from a place where its not that easy to source a decent amp clamp (though Multimeters are easily available) and your video has really helped me and several others stuck in a similar situation.
Cheers,
A.P.
Hey thanks for this. I really appreciate you taking the time to share this.
Your a boss, bro, thanks. Thanks for being so smart and helping us poor folks. I have money and I work, but money is tight and cannot be wasted. Good job, GOD BLESS
Nowadays, ampclamps are nowhere near as expensive as they used to be and the purchase of an ampclamp is a good investment for any homeowner.
A very good video, thank you.. It shows the general operating principal of a current shunt which are a vital component in many electronic devices. When I build heavy duty power supplies I usually buy premade ones which are solid brass and calibrated, however for the smaller supplies I use a piece of wire of the same length on all of the models, and wire up a stand along milivolt meter which says it measures amperage on the display. It's wired just like you have here except made permanent with soldering.
Just take off the positive battery cable while the car is running. If engine stays running, the alt. is good.
Larry Zoch a
@@larryzoch4344But this isn't true on older models pre sensors and fuel injection is it?
I learned way more than what I needed, very useful info! thank you!
Very good. I'll go out into the garage and do it. Just installed amplifiers for new radio system.
You made a current shant reading meter, You are genius
I love your videos very helpful and no bs.
It's always great to learn something new everyday thank you for sharing that knowledge I'm very thankful and grateful for it I hope you post more videos about things like that
Works for big jumps in current draw I found. I had a hard time finding that sweet spot you mentioned. So I just tapped off not far from the on clamp. Basically the greater the distance you spread your volt meter leads for the pick off the higher the millivolt reading you will get. At least that's what I was seeing. I didn't find it was very useful or accurate in the 10's of amps range, but 20's to 200's you will def see a jump and a big change in that millivolt reading if you turn on say an 1600w inverter with a 1600w load like a heat gun, which is just what I have in my company truck since I do avionics work on Helicopters sometimes remote in the field. Thanks for the vid. I found it useful.
I like your vid even though I just bought a clamp meter that I can also use as a general function multimeter. I just like the idea of not having to disconnect anything to take measurements.
Your video however, taught me a few things and for that, I'll indeed subscribe. Thanks for making this.
Thanks, good video...
I used to load-test PC power-supplies and needed a way to measure the load. That's where the shunt would come in, and I could then attach a mili-volt meter across the shunt, instead of a DMM..
It's the same principle, but using analog guages,,,
Well done, sir - well done indeed.
Lots of guys commenting on how an alternator's output may be, say 130amps, but the system may only demand 85amps for charging, a/c, lights, or stereo, etc. You may have leaky connections. Where do all those extra amps _go?_
Easiest way to find out is to slide a piece of cardboard under the car when you pull into the driveway. Next day, pull the cardboard out and look for any extra amps that leaked out overnight. They're silvery, shiny, and may leave tiny burn marks.
really nice video, keep up the fantastic work
Yes this works. Thanks for the idea...
Great video...simple n straight to the point..thnks very helpfull
Great idea, it was very useful. Thank you so much.
Well done i have never herd it put so concise and pertinent thank you
Very nifty trick ~ The way you did that wire !
Brilliant, very impressive. Thanks for sharing!
Another tool is always handy. Iwill defo make this, I have all the bits in garage inc multimeter.
Nice approach. Thank you.
Thanks.thats what i needed to know.to upgrade my wiring and alt.on 79 chevy
Great video. New you could make a shunt but did not no how to calibrate it.😀
Nice trick, but instead of using this testing cable and "calibrating" it, it is much simpler to use the procedure you describe by using the car's negative cable that goes from the battery to the chassis and measure mV across this cable directly. Calibration can be done in the same way. By putting a bulb of known current draw across the battery terminals and reading the resulting millivolts on the multimeter. Then, this value is the reference value for every new load measurement, by applying the arithmetic analogy method, that is, for the (say) 21 Watt lamp I used as a reference, I measure (say) 15 millivolts as translated current. Now that my new measurement is (say) 86 mV, how much is my new current? In this way one does not need the external testing cable and its calibration making things easier and simpler, while the general idea remains the same. Anyway, your presentation is correct. Thanks for sharing the idea. Personally I am using it for many years now whenever I suspect something wrong with the electrical system of the car. Moreover, one can detect even the slightest parasitic current drain of the car's system, provided that the multimeter he uses is of a good brand name, with proper measurement properties for that purpose i.e. high accuracy in the millivolt range. In this last case, only the immobiliser current draw (which must be known beforehand) should be measured when the car in in a "key off - motor off" status. Any other indication in excess of the (known) value will represent a failure (i.e. parasitic current draw) of the system needing further investigation...
this is a good video to teaching 99.0000000000000000000000000%the electrician's and 99.000000000% the technician's what is OHMS LAW
This helped me go back to sleep after taking a leak at 0200 hrs.
SOLID VALUE in a video...
You can connect each clamp to one battery post, and use it as a nice heater. Life hack ;)
Brilliant mate! Cheers
Thanks for the info awesome video thanks guys!!!
As my brother would say, while holding his arms out wide, you have brains out to here!
Thank you sir. Hope you enjoyed!!
Thanks for sharing this video.
Very nice, it would be a nice teaching aid
Very clever idea
Lol that’s EXACTLY who gifts you those cheap jumper cables. And she’s damn proud of it too!!
very good could be improved for your interest my 67 Ford Cortina 1500 GT had a built-in current clamp meter you can make a current clamp meter using a multimeter
I am happy with the explanation. At last someone talking about amperage when testing the car alternator.
This is genius. You just saved me $50. Thanks!
Anytime bro.
U saved money; u learned a principle; your value increased; you can pass along for free either a new lesson and or loan this new tool or both with no worries. The plastic " i can buy one at my local Chinese bulk parts distributor" crowd miss this whole opportunity. Right? 👍
I should have shuntin knew this.
Awsome video.
You've earned my subscribe and like! ! For sure! !
Nice channel-locks. I have the same pair that I carry on my person a majority of the time. Almost feel kinda naked without them.
Great video as well!
I believe those are knipex and not channel lock tho right?
They are very useful and can loosen many bolts that pliers just won't touch
Cool thanks man... I love tricks like this. Yeah if you cost in time spent and you're busy then buy a clamp but if you're retired or time rich DIY and wanna watch the wallet, then a quid saved is a quid earned! (+Satisfaction factor!) 😎
Great tips. 👍
That is AWESOME. ...!!!!.....SHUNT LIFE!!!!!
so good. thank you
good job ,,,my friend,,
Awesome brother!! Thank you
Great video I would just like to add that a good volt meter that reads acurate MV's aint that cheap either . AND the price for a fair clamp meterThat reads AMPs DC can be round same price as a good volt meter that reads acurate MV"s. So with that I have to say this video is by far the most clever I have seen thus far on youtube KEEP EM COMING BRO cool accent too lol 10 thumbs up for YOU! Check cheaper clamp meters on Amazon that read amperage I picked one up for $27
Pretty cool video.
This is an ode to the death of overthinking.
That's pretty cool!
If you don't need over 100 amps I recommend the uni-t ut210e it can do dc current up to 100 amps and is pretty accurate even at small currents like under 1 amp if you need that I have one and have been happy with it and it's under $50 but make sure you get the E because they have others but they don't do DC current
I am reminded that I don't know as much about alternators as I thought. Thanks. Back to finding out why my alternator won't charge at idle with the headlights on and heater full blast with a 130 amp gen 3 mustang alternator. I am thinking its the grounds?
I am going to be testing a vehicle with 2 batteries. What difference's should I take for hooking up shunt, multimeter, etc,etc. Do I isolate to one battery or does it matter. Thank you in advance. And thank you for a very clear and valuable presentation.
Well done.
Thank you.
just wow. thank you.
Sears sells their amp clamp for about $60. It measure AC/DC amps, voltage, resistance, freq., and continuity (with sound).
joe r what is a sears?
Sears, Roebuck, and Company.
joe r I’ve heard of them...it’s a shame they aren’t around any more, poor mgmt probably ran them into the ground I’m guessing.
They ARE still around though few and far between. I still believe you can order that meter.
Thanks so much
Nice video
Good Video
bravo, thank you
Thanks for the video its just that amp meters so cheap these days so I don't think people would go this way to test but I like the way u calibrated the wire i just never kn a wire that gage could have that kind of resistance in such a short distance.
D.C. Amp meters, not so cheap. especially clamp meters.
22.99 harbor freight
SMART THANKS
Good of you too share a thing like that.. as let's be honest if sombody didnt take the time to show how to so do that.... you would never have come up with it...👍👍
Awesome new to me.
thank you
Tell us something on the small jump-start how they work how they produce the power thank you indeed
Thanks!!
THANKS
Amazing🎉
So, the amp clamp we can put over the red Alternator wire and check?????? 😊 Or????
Very Good
Please Iwant diagram for your method of cheak charg
Thanks
U can get claim meter for $50 you have everything what you need right in one tool. AC & DC reading, Continuity, ohm and even temperature
if battery is fully charged what would be the charging current when testing on the negative lead be.is there a figure for a good battery.
Nice
So to be clear, you started off with a long thick(ish) cable with crocodile clips connected to both ends which you then cut off, shortened the cable and bodged two more clips onto?
Excellent; I'll have to watch it a few times, but thank you. A wee diagram would be fab...Thanks mate.
make your own diagram on paper with basic instructions. I did and it will be easier than trying to deal with a phone or going back inside to revue vid.
Thanks mate:-)
Pretty neat! if to complicated Advance Auto will load test your alternator for free.
Yeah...they tested mine today. I love Advance Auto!
I've never trusted parts stores to diagnose vehicles and components.