How to Properly Test an Alternator (The Extra Steps the Parts Store Can’t Do)

[@spelunkerd]

This is the classical old school testing I was taught. I find it surprising how often working pros today on KZbin don't bother. As soon as they see lack of charging they stop and order parts. New cars are much more difficult to do testing on. The alternator is often hard to reach, and the signals between PCM and alternator are much more complex. Even so, I think drop testing of the power and ground side are worth doing.

[@scientist100]

They have LIN lines to the PCM lol, could not believe 3 alternators later from the parts store did not fix a charging issue, it kept dying, only solution was to replace the alternator from the dealer (OEM), this was for a 2013 Honda Oydssey.

[@shadetreec6013]

​@@scientist100a little newer than 2013 Honda can show below battery voltage at idle normal operation

[@scientist100]

@@shadetreec6013 the car would show a battery charge issue at the dash. The OEM one fixed it.

[@truckladders4104]

Great video,Im a 30 year heavy and auto mechanic still learned alot! Keep up this type of video, you can never know to much !

[@williammargrave4891]

Thank you for taking the time. I am a master tech in TN and i like to watch this kind of stuff to stay on top of it so I dont get to over confident.

[@pontiacsrule8761]

Great video as usual. Just remember a lot of us aren't in a shop. We are DIYers. That's why we watch these channels. Many of us don't own a lab scope. Many of us own a voltmeter. Try at all cost to teach us with basic tools if at all possible .Lots of time we condemn a alternator if the output voltage is low still at the terminal on alternator. We can't check to see it the PCM is controlling the input. I personally love the videos. Great story about the broken motor mount. Would of never thought about that. Also, thanks for your honesty about when cars come back to bite you. That's what makes your channel so good. Andy

[@chipvickery5078]

It's not impossible to check for pcm control with a meter if you know how the meter works and what you should expect to see. If you don't know then you should take it to a professional like this guy is. Or load your parts cannon..your call.

[@marianodeocampo5569]

You can check for reference and or ohm out sensors or the cable itself from PCM to connector to verify the connection on continuity. You can check the pin at the PCM, voltage drop, all can be done with a DVOM to give you the average readings, but a oscilloscope is king, even if you buy the budget Uscope, sub $225 w shipping, you too can perform simple tests. It’s not too difficult

[@devilsnetwork4212]

You need a scope to properly diagnose vehicles nowadays unless you are someone sort of super human that can record voltage every 20 milliseconds and graph it in your head.

[@ThunderbirdRocket]

Better than a textbook ! You have a lot of knowledge ! Thanks for sharing this very clear lesson !!

[@SeanBZA]

New subscriber, and all great points people overlook. Especially about testing diodes, which people almost always, even experienced mechanics, overlook. Depending on the multimeter you can switch to AC volts, and some have a dual display, which will show both DC volts and the AC voltage on it, so that you can diagnose a failed diode pack without a scope. Others when in AC volts disregard the DC, so you get the AC voltage only. As well remember that there are 9 diodes in the alternator, 6 high current ones that feed the output, and 3 lower current ones that provide the excitation to the rotor, and those 3 also can have a diode fail. Most voltage regulators will have a terminal, or a place you can put a probe, to measure that field voltage as well, so your scope can test those diodes as well.

[@AlHasenfratz]

Valuable procedures that really enhance accurate diagnosis ! Have seen quite a few no charge conditions corrected with a new alternator recur, due to bad grounds at the mounting bracket. Changing the part restored operation, for a while.... Read somewhere that half the warranty returned alternators actually are not defective. Sounds plausible? Voltage drop is king!---------Al.

[@crttz44]

As a big fan just to clarify 0.090 is 90 millivolts not 900 mil volts and half a volt would be 500 mil volts so if he was at 900 mil volts he would be over but at 90 mil volts he is ok ........very well detailed course on alternator diag ....I actually got a ram 1500 a month ago with exactly as he talks about, a defective pcm not activating or pulse with modulating the alt sent to us , after another shop had replaced it and could not figure out the problem. We solved it and ordered a reman pcm waited two weeks to recieve it,solved the charging issue but needed to tow to the dealer for programing cause we are not equiped to flash program pcm,s at this time.

[@alrightythen888]

I was going to write something similar. 0.09 sounds like its higher than half a volt. And depending on your multimeter settings it may actually read 9 or 900. I would want to see what half a volt looks like on the multimeter as a reference and the detailed setting to use. Anyhow, most drivers can't do the AC ripple test because their multimeter leads are not long.

[@anthonysova7117]

Very good point about loading the circuit you’re checking for voltage drop it takes BOTH current and resistance to create a vd One question about A/C ripple why wasn’t the generator tested loaded and unloaded? Does the 0.5vac ripple still not exceed 0.5 loaded? CHEERS

[@DayClanTribe]

The more current flow you have during the test the easier it is to see. So you want to load the circuit.

[@mamjacobs1983]

I must say from all the mechanics I watch on youtube, you explain t8he things at best. Keep up the good work

[@dnlmachine4287]

Top quality channel. A great source of information. Hopefully people can learn and share from this for years and years to come. Stay gold.

[@djosbun]

Superb teaching skills!

[@scientist100]

Good, refresh on the basics and tets methodologies.

[@BenKlassen1]

Thanks. This channel is a gem. You are a master teacher!

[@mikedavidson2117]

What do you do with a 2015 Buick enclave where the converter is in the of the starter I’m sure there are other ones also

[@niallseddon8657]

Always worth checking voltage drop from battery post to battery terminal

[@CoreyPfeiffer-h4p]

"LET'S SEE A TOOL BOX TOUR" LOVE YOU GUYS. YOU'VE CHANGED HOW I DO THINGS.

[@theroyaltyautoservice]

We will add that to the list! Professor is waiting for an add on to it which is why he hasn’t done it yet. He wants to do it with that on there. Lol

[@bernardocisneros4402]

Great video with a lot of valuable and practical info. Do you also put a clamp-on ammeter around the B+ cable while loading the system with hi-beams, A/C, radio etc. to see alternator amp output or is it not necessary? Or is that done by the big Snap On battery tester?

[@kevinkeown4312]

One other charge problem to check is the drive belt for the aultonator is it tight enough .good video though

[@henridekker9132]

Great Video. Always something new to learn.

[@mechboy5954]

This is the kind if gentleman that will throw you out his shop if you approach him with "I read this is the problem on forums" Pay this gentlemans Diagnosis fee, let him repair it and move on with your life

[@thyreaper650]

The voltage drop with ur standard meter like you used wont tell you if you have a bad ripple causing running issues will it? Is there a way to see it without a scope?

[@thomasherring6640]

Just to be clear, the same thing applies to testing the starter that applies to the alternator. When you are testing power and ground to starter, you need to have someone trying to crank the engine so that there is a load on the circuit. You can have a power or ground test absolutely fine with no load, and go completely open when loaded. This applies to any electrical circuit, always test for voltage drop with the circuit loaded.

[@thelifescout8335]

My 18' Hyundai Elantra will idle with loads on at 12.8 volts all day long, it does not start charging the battery until cruise deceleration. This is why ( along with other strategies) this 2.0 NA Port fuel injection engine got me 48 MPG commuting back n forth to work everyday. If you didnt RTFM and went by old school rule of thumb of 13.5-14.5v youd probably think the alternator was bad.

[@abdul-kabiralegbe5660]

Hondas and Acuras also output about 12.8V or so when the system detects that the battery is full or the battery temperature is too low (or high, I forget which).

[@thelifescout8335]

I checked my wifes 22 passport and at hot idle loads on it was outputting 14.6. I was expecting what you mentioned. however for her system I didnt take the time to read up on it. @@abdul-kabiralegbe5660

[@SeanBZA]

@@abdul-kabiralegbe5660 12V8 with high engine compartment temperature is correct with a fully charged lead acid battery, as the terminal voltage, which with a fully charged battery is 13V8 at 25C, is going to drop as the temperature rises. Older alternators that charged at a fixed voltage, 14V4, or 13V8, irrespective of temperature, thus would overcharge the battery, causing it to lose electrolyte due to it being split into hydrogen and oxygen. Some sealed batteries, and some more expensive refillable ones, have a palladium catalyst in the vents to recombine this to water, slowing down the loss, but you always had to add pure water to the battery to give it a long life. Thus checking the battery water, and filling up at each service. Sealed batteries are the exact same now, just there is often a cover over the screw off caps, and they say sealed for life, as they know there is enough water there to get you out of warranty before a cell boils dry, and you buy a new battery. Pull off the label, see the caps, and check the water, and you get many years more service out of them, and check the water monthly as well, even if it means you have to remove the hold down and the terminals to get to the caps. Done that to all mine, and got to see that they would last 5 years just filling up every 6 months or so, all cells taking around 100ml of water to fill up again. Otherwise would have had the battery fail around 25 months after buying, just outside the 24 month warranty. OEM battery had caps, but was never checked, despite it being part of the OEM service routine.

[@rauls300ce]

@@abdul-kabiralegbe5660 Toyota /Lexus do the same.voltage stay very low, but if you turn the AC or lights, voltage goes up from 12.8 to 14+ But you need a min/Max meter to be able to see it.

[@retireditguy9493]

Great Video on test methodology. At times 14:55 and 15:50 you referred to a meter reading of 0.09 as 900 millivolts. Isn’t that 90 millivolts or am I missing something reading your meter?

[@paulspooner-q6k]

i think doing a video and talking you will say the wrong thing. 0.090 is 90mv which is very good. 0.9 is 9 tenths or 900mv would equal getting bad. he just made a simple mistake trying to talk and video I've done it myself

[@theroyaltyautoservice]

Yes you’re correct. Misspoke there. Sorry about that. Thanks for watching!

[@erichkaanikin3555]

@@theroyaltyautoservicesorry, I’m still confused. Is the correct reading supposed to be .5 or less?

[@robhunter2435]

yes 500mV or .5 volts@@erichkaanikin3555

[@THEDRAGONBOOSTER8]

Great video.Thanks for sharing your experience..

[@DD-gd3fr]

Great diagnostics ,I'm learning how to use a scope,could you tell me please what is a good affordable scope? Thanks

[@zenoviyleskiv5858]

I have 2020 Nissan Murano few days ago barely made it home alternator was not charging and battery was discharged. I tested and I assumed it was bad alternator. It turns out now I still have the same problem with the new alternator. The plug on the alternator has two wires one of them has 12 V coming directly from the battery and another one has 12 V comingfrom the ignition switch so I did test that and it’s good but when I start the car, it will have 14 V and then a few seconds it will die down and I’m really confused. What’s my next step.

[@DontrellHammond-oj1bb]

Thank you for the info

[@westcoasttools5179]

How were leads set up on the alternator when you were using the Zeus for ac ripple?

[@theroyaltyautoservice]

Positive on the battery lug on alternator and negative on the alternator case.

[@AdrianFerguson-v1y]

Its also a reman 105 amp alternator i got to replace it. It has aftermarket ignition coils idk if that would have anything to do with it

[@charlesabura472]

First and foremost, thanks for the great video. I noticed a little issue: 0.09 volts is 90 millivolts(not 900 millivolts)

[@Mr2004MCSS]

I was thinking the same thing too especially after he said he didn't want to see anything over 1/2 a volt which is 500 milivolts and 900 milivolts is almost a volt.

[@charlesabura472]

@@Mr2004MCSS I think it was just a slip up - he hasn't made videos in a while😅

[@theroyaltyautoservice]

Yes it was a slip up. Sorry about that.

[@charlesabura472]

@@theroyaltyautoservice great, we all make mistakes. Thanks again for the awesome video.

[@johnavila7942]

Totally agree

[@PaulCTownsend]

Grade info thank you.

[@vickenkaragozian2041]

That's 90 mV. not 900 mV..🙂. Thanks for sharing.

[@theroyaltyautoservice]

Yes you’re correct. Misspoke there. Sorry about that!

[@vickenkaragozian2041]

@@theroyaltyautoservice no problem. Keep posting new videos. Have a great weekend. 👍

[@johnhill3644]

would a pico 4425a scope work just by zooming in also. we're supposed to be buying 9ne

[@johnhicks3797]

What about on a European care like a volvo where the battery is in the trunk do you still need to go directly to the battery or can you use the designated post in the engine bay.

[@johnhicks3797]

I guess also if you have to use a jumper do you minus the voltage drop across the length of wire you are using

[@electron-1979]

No, because a voltage measurement draws very very little current (amps), the voltage drop across the meter and leads is negligable. See Ohms law, Voltage = Currents (Amps) x Resistance (Ohms). So if there is no current (Amps), there is no Voltage drop.

[@electron-1979]

As for the battery in the trunk, you should check for voltage drop between the battery (on the actual lead battery post) and the engine post, too

[@harveywalker1560]

I am old (77) shade tree guy and love these. Don't have a scan tool, but thinking about getting a LUNCHX431 CRP919BT would like to know what you think about it. I am on ss so money is one reason for this one.

[@superd0fad0]

Most of DIYs don't have access to such sophisticated test equipment(s).

[@SeanBZA]

But a multimeter is cheap, or even free at Horror Fraught, and well worth keeping in the vehicle, the free Harbour Freight one is good enough to use here, and accurate enough. Blow it up, get another.

[@JamesSmith-xs7sr]

I fixed the charging problen in Oscar Goldmans 85 500 sel MBZ. I just replaced the "brush pack", she's back up to 14.23 volts!

[@zaraahmad5618]

when is AC part 2 is coming?

[@Peter-tf2uc]

Thank you for a detailed video

[@chipvickery5078]

Awesome video sir!!!

[@DD-gd3fr]

Is .5 volts a standard for most circuits? Thank you . I wish I worked for you when I was young a work comercial😅. I'm a retired DIY now. Enjoy all your vids

[@ThePortadump]

In terms of a voltage drop yes, any drop less than 0.5 can be attributed to the resistance of the leads on the meter - which is why you should always check your leads.

[@mikerossman9863]

A simple Fluke meter can do what you need if you know how to use it.

[@jonathannagela2130]

When you "diagnose" a bad diode or diodes you replace them right> or do you buy an alternator?

[@ddblairco]

thank you

[@mayowaodus6310]

What’s the maximum voltage drop on both the negative and positive post of the alternator and us this value cut across all brands

[@SeanBZA]

Should be in total under 0.5V, if more check for good connections and corrosion. Remember this includes both battery to alternator, and starter, plus the fusible links that are typically used, plus the ground cable from engine to frame, and the ground cable from frame to battery. most often engine ground, and battery to frame, is the one neglected, and often one is poor contact. Remove the chassis connection, clean the terminal lug, the bodywork there, and apply a thin film of grease ( white grease, dielectric grease, Vaseline, wheel bearing grease, or even gear oil or engine oil at last resort), and put the connection back, and make sure the nut is clean on the contact face as well. There are often TSB's about this, famous on GM products as they age, and covering multiple models and years. Same for the fusible links and multifuse units, undo, clean the contacts, retension for the plug in ones, and clean and reconnect both with a thin film of grease on all mating surfaces.

[@electron-1979]

​Nooooooo! Clean, tighten, then spray with paint or fluid film. Don't put non-conductive stuff between connections!

[@hillbilly3366]

Keep 'em coming my friend. Any day is a good day if I can learn something. Also if I'm not mistaken, and I am often, the reason you see the upper side of the AC ripple at all is because the rectifier circuit is a half wave rectifier. Seems like manufacturers would clean up that half wave ripple with a full wave rectifier and have a "pure" DC signal from the alternator. Just my uneducated opinion.....

[@paulspooner-q6k]

from my knowledge it has a full wave rectifier but it has to have filtering after that to get that pure straight waveform and the battery is acting like a filter as well

[@SeanBZA]

No, that is a full wave 3 phase rectifier, as diodes are a lot cheaper than copper, so putting in 6 diodes, and only half the number of turns of thick copper (or for the cheap alternators the thicker CCA wire) to get the rated current output, is a lot cheaper than having to put in double the number of wire. Then make a larger case to fit them, and having to get much more expensive diodes, rated at 200V, as opposed to the regular diodes that are rated at 30V, and are designed to break over at around 40V, to handle the case of a load dump transient (which is part of the job of the alternator now, as electronics in a vehicle is so much more than when a generator was around to drive only a few lights and a coil with points), or a regulator failing and causing the alternator to go to full output. Ripple you see there 6 peaks per revolution of the alternator field past the pole pieces, because of the 2 phases, and at any time 2 diodes are conducting at the peak. The larger lower ripple is because of the rotor turning once in the housing, and also the slower response of the voltage regulator modulating the average output voltage, as it is being aimed at a particular set voltage by the internal regulator module. Typically 14V4 when cold, and dropping to 13V8 as the regulator heats up, to closely track the actual battery temperature, but still provide a high initial current to charge the battery from cold, tapering off with time. With modern alternators getting controlled from the ECU the initial voltage set is zero for a few second,s to allow the ECU to gain control of idle RPM correctly, and start the cold start warm up and keep emissions down, then it is ramped up to get voltage to 14V4 for a few minutes, to provide a full charge to the battery. Maintained till the ECU sees the battery current start to taper off, as the battery approached full charge, sensed by the sensor on the ground lead. Then it will depending on the model, either switch to a 15V charge for a few minutes, to desuplhate the battery, set by a counter programmed per the OEM battery manufacturer as to best profile for this, or will drop the battery voltage to a set voltage as determined by ambient inlet air temperature, and engine compartment temperature (coolant return temperature) so as to not overcharge the battery, and all the time monitoring, so that the sensed ground current in the battery is close to zero, so the alternator provides all the engine and vehicle current draw. this means that your alternator warning light comes on when the ECU detects the battery is being forced to provide current for more than 5 seconds, either due to the engine not running, or that the load exceeds the output 5 seconds after it has been commanded past 95% duty cycle on, and the alternator is not supplying this current.

[@hillbilly3366]

As an addendum to my first reply, I actually love it when someone has a lot more knowledge than me and is willing to share it. Thank you for the replies.

[@michaeldiaz6308]

My brother has an HHR with the battery in the back (trunk area, below the spare). How could we do these tests with the alternator and battery this far from each other? We have a hunch that it’s the alternator.

[@robertfrancisco1193]

would you trust a SCAN TOOL WITH A BT506 AUTEL HOOKUP ? I HAVE BEEN CHECKING WITH THAT SETUP AND GET ALTERNATOR INFO WITH BATTERY VOLTAGE. but i dont know how accurate it is. i see your way is spot on.

[@AdrianFerguson-v1y]

Man ive got an 02 mustang Gt new alternator and battery and not charging still. Connections look ok, tested engine block ground and all ok. Still draining the battery fast. When i turn the ac on it drains it really fast idk what to do

[@travisevans7502]

Why would a motor mount stop the ground? Shouldn't the engine have a ground strap going to chassis?

[@billymach4]

Thank you for the complete end to end explanation. DIYer here. I don't have a scope just a multimeter. Is it necessary for me to invest in a scope? I have relied on the multimeter so far.

[@theroyaltyautoservice]

The scope is a massive resource to have. Start small. You don’t have to start by buying the ATS. Have you seen our video with the 3 channel scope? Might be a good place to start for you.

[@billymach4]

@@theroyaltyautoservice I will look for that video!

[@Poncho12313]

Could the show the PCM control wave ?

[@abdul-kabiralegbe5660]

It varies from manufacturer to manufacturer. Some like Fords have 2 wires going to the computer but most others have just 1 (out of the several tiny wires on the alternator connector).

[@bradleykennell9949]

I did not know it was possible to do an AC ripple test while testing DC voltage at the B+ terminal of alternator. Interesting! It was good to see someone else struggling with tangled leads about 13:30. I have the 10 ft. picoscope leads and have yet to find a good way to store them. Anyone have suggestions?? =)

[@porceder]

We wire tie the 2 leads every foot which saves some tangles as it's like a thicker cable.

[@robertmobileman8304]

Great video RAS

[@johnavila7942]

Great video

[@DependableAutoTruck]

thanks for sharing doesn't the computer control the fielding wish you would go thru that. also would be nice to see how E-Scan compares to like snapon scanner for diag codes on cars

[@jtjones4727]

Generally speaking, you could just check service data for theory of operation. Most of your newer vehicles are going to use computer controlled alternators, and more often than not, they use a PWM type of control system. And a lot of your newish vehicles will also use a Battery Monitor sensor, which is just a glorified amp clamp. They tend to just monitor the current being used or put back into the battery and under load, the computer will use a higher pulse width signal for a higher load, and lower pulse width for less load. You only need a cheapo scope for most alternator tests. You could use a $150 dollar Hantek scope or a handheld Owon for example. I have the Owon HDS200 series, the HDS270 I think, it's not beside me at the moment. I love that thing, it's a handheld 2 channel scopemeter. It has both a digital meter so you can check resistance and typical meter stuff, and a 2 channal scope. It's actually good enough to check CAN bus signals, I use that thing all the time.

[@malizia63]

Could you see the ripple on an old school analog meter ( like Simpson)?

[@shamessun]

Thank you

[@jessemackenzie6516]

Love the ATS vids...

[@josephlundy3534]

Been there done that , condemned the alt.. Wrongo ! A broken control wire who's circuit goes through the charge gauge on the dash !😮

[@JoseRamirez-ie2bk]

Thank you sr🫡

[@yahyaahmad5502]

when AC Part 2 is comming?

[@theroyaltyautoservice]

It’s on the way! We’ve been so busy at the shop and just needed some time to catch up. Sorry!

[@Mac-t4y]

The reason part stores offers free battery and alternator test so they sell parts, especially the battery price is almost double the price of Walmart or Costco.

[@thatrealba]

I could NEVER grasp all this by trying to learn from a book by myself. My auto shop teacher in high school could teach like this. Too bad I was only there for my freshman year.

[@autoservice6572]

Thanks , wait for more more informative lessons , test don't gess is my slogan

[@mikeburdi3464]

Test don't guess, has been used by Paul Danner (scanner Danner) for about 20 years now. Other people in the trade are now using it more, which is fine as long as they adhere to it!

[@autoservice6572]

@@mikeburdi3464 please don't misunderstand my comment , i mean i'm also use it , thanks

[@mikeburdi3464]

@@autoservice6572 it's all good my friend. Like I said, many people are using it now, which is fine. But we have to live by it and not just speak it. Good luck on your business, I hope you have lots of success!

[@martinarrieta248]

Grasias

[@WillKlaver]

.. i got one that works but the Bearings squeal first start for a minute so i gotta replace it Anyway before it seizes & smokes the Belt off.. ⚡

[@neutrodyne]

The decoupler on an alternator can cause you headaches. The customer comes in and says the charge light on the dash comes on at times. You do all of the above tests and everything checks out fine. Then you finally discover the Alternator Decoupler is at times slipping and thus triggering the computer that there is a fault.

[@necrobusher]

Thank u teacher I just need to afford the ats oscilloscope 😅 Too many brokies to count

[@aymenmohamed1134]

Awesome

[@yahyaahmad2582]

When is A/C parts 2 is coming?

[@t.k5928]

I think you might need a new camera. It’s kind of blurry. Or maybe a setting. Sorry I’m not too familiar with camera work.

[@abdul-kabiralegbe5660]

I think it's just this video or maybe they used a different camera for this video.

[@t.k5928]

I think I’ve seen it on every video that they put out

[@abdul-kabiralegbe5660]

@@t.k5928 Maybe the outdoor location for this video made it more apparent here.

[@theroyaltyautoservice]

It was the location being outside that affected this video. As you can see I was trying to move around a lot to get rid of the glare. All the bays were full because the shop has been crazy busy but we wanted to get a video done. Hopefully we won’t have to do the next one outside. 😬

[@tibortorok6343]

👌

[@jeffryblackmon4846]

Just a small error- .090 is 90 millivolts.

[@jonathannagela2130]

you should break the fusible link and then perform the tests with it broken.

[@DuaneDonaldson]

The name of your video is very misleading, it does not cover late model LIN controlled alternators. For example when the LIN is bad but the alternator is charging by default, the owner does not know there is an actual problem overcharging the battery and killing it over time. Changing a LIN alternator with the wrong aftermarket part number where the LIN Header is wrong and it will not talk to the ECM, this Header can be seen on a scope waveform, and in my opinion, the #1 problem with replacing alternators, the store sells the wrong application way too many times since they do not look at the LIN Header nor do they care. Can you please do another video covering such LIN examples? The overall waveform on the Alternator LIN wire will show if more than one LIN component is on that line, based on more than one Header, which is easy to read based on the first few pulses, and based on codes will point to a problem on this overall circuit, and we might see the missing Header signature of a specific component, problem found. Another reason why we need waveform captures in our customized library. cheers.

[@alexismarcyting5340]

when part 2 of the a/c?

[@briteidea08]

As someone who has spent time in retail auto parts stores. Even if someone’s alternator supposedly tested bad. I would still refer them to a shop. Because of bad grounds or many other reasons. Unless it’s a bench test. So many people comes to the stores. Think the free testing is gospel. Unfortunately there’s many people who work in these stores who think the same. Those free tests are a direction to go. Not gospel.

[@stevemilo6935]

Doing this stuff for a living is painful and boring.

[@electron-1979]

Even Eric from South Main Auto doesn't like working on cars!

[@Quickwaya]

Great video, however you had 9/100's not 9/10's v drop (.09 not .09). you said it correctly at first then said it incorrectly LOL hense I think why camera man (your son) corrected lol . 9/10 is ovee a 1/2 volt. No worries it my anal retentive nature lol. Also while not as accurate as the scope you can see triple voltage to determine a bad diode by puting your fluke 87 V (even the (I see yours is the 88 V and I believe it will do the same has the same jacks and has low enough resolution and fast enough response time to capture (87 V capture response is 100ms which is typically fast enough to catch bad or failing diode or diodes that will cause a problem), put neg on body of alt and pos on alt batt lug with red lead in V/1/2 jack ( great point NOT the terminal or nut, just as true for batt term's or any other connection point (always done stream as you want to test connection point)) with meter in AC lowest voltage reading (auto or manual whichever gives the lowest reading) and loaded down ( lights A/C and Rear Defog or as I say defrog :) ) and you can see ripple if any are going bad. Again should not be above 500 mV (.5v). Not nearly as good as a scope - but in the field where a scope may not be acceseable and something is better than nothing this will can give a good indicator. Try it out!! Let me know what you see. Was actually hoping that you would have demonstrated this. Again check it out on a good know and a bad known with your 88V and let me know what you get and think as well as on a 87 V if any has one. Understand not all multimeter will have a fast enough response time. However I must confess I prefer the scope as they is indispensable with the changing technology and with far better response time (10ms or less) and resolution typically.

[@richardwallinger1683]

sawyour hairdooo bye bye

[@TekkHakk]

Yeah, I'll run out and buy a $20k scanner and $4k oscilloscope to replace an AutoZone $80 crap alternator smdh 🤦👎

[@paulspooner-q6k]

yes sometimes that may fix it, but now the pcm is in control of the new alternators and its a digital signal being transmitted so you can get a cheap scope for that, but just replacing that cheap alternator is just a guess .when that cheap alternator does not fix it then that's when knowledge and the right equipment being used will fix it. hey its the car manufacturing doing this to you not us, we don't like what they are doing either. i do this same testing so i buy old school cars so i don't have to deal with it for myself

[@robertnicholson771]

I understand what you're saying, but I replaced a friend's alternator in a Honda minivan and a rebuilt was $300. Everything is expensive these days.

[@johnmon94]

And what will you do when the “cheap” alternator doesn’t fix the charging system?

[@johnriley7053]

Shout out to Bernie Thompson 🫡