Alternator Testing - GM

Come along with Eric O. as he has a look at this 2005 Chevy 2500HD 6.0. The Check Charging System indicator (battery light) is on and we suspect the alternator has failed. The question is, how do you know if it is the alternator, the belt, the battery, corrosion, a broken wire or the ecm? Simple, you test it! --Enjoy!
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THANKS A MILLION!!
--Eric O.
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South Main Auto Repair
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Disclaimer:
Due to factors beyond the control of South Main Auto Repair, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. South Main Auto Repair assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. South Main Auto Repair recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of South Main Auto Repair, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not South Main Auto Repair.

[@spelunkerd]

What we all look for in a mechanic: Tests devices to be sure they can't be fixed and need to be replaced. Check. Tests adjacent wiring to be sure of the diagnosis. Check. Willing to admit when he makes a mistake, like ordering the wrong part. Check. Doesn't blame underlings, who put effort into teamwork. Check. Makes potentially complex tasks look simple and easy. Check. Not always hunting for extra work to pad the customers bill. Check. Has fun on the job, relaxed and joking, not overwhelmed with juggling details. Check. Any wonder this channel is so popular?

[@crisprtalk6963]

well stated!!

[@wyattoneable]

As a professional viewer I can tell you we like certain consistencies. Your introduction, brake clean and your "If I can do it, you can do it". This was a simple procedure but add the computer control aspect and your DIY'er viewers will perk up. Plus your frustrations are appreciated because it validates our frustrations of doing our own repairs. Your doing great work on this channel and in your shop.

[@SouthMainAuto]

Thanks Wyatt. You still coming in Aug right?

[@wyattoneable]

South Main Auto Repair 100% Brother, I'll be there.

[@geraldsanford2411]

it validates we are all human and we all make mistakes but still great Video ERIC O AND THANKS

[@randytravis3998]

@@SouthMainAuto had a mini van years ago ,, all the front lights started going out about the same time ,, about a inch from the connector on all the marker and turn signal wires there was a hole and Green puss ,,, about 10 or 12 wires I had to fix ,, wish the person that had probed all the wires used that can you did too plug the pinch spot in the wires ,, another Great Video ..

[@bborkzilla]

I hope the stupidity from all the lunch break cubicle mechanics won't discourage you from making videos. This is one of the best car channels on YT, hands down.

[@throttlebottle5906]

arm chair input hasn't stopped him before, why would it now? :))

[@SouthMainAuto]

bahhh I don't care I just keep on truckin

[@1967lathrop]

This guy is one of the most honest and moral mechanics I have ever seen. I’m proud to have a chance to watch his content.

[@isaiaholveda6599]

@@1967lathrop lli IP

[@isaiaholveda6599]

@RUSH & CO. o P lo jrriorrjjjj IP pi l Ml r

[@cehuddl]

Eric I thank you for taking the time to video all the details of this repair. You have no idea how helpful you are and how much you teach us DIYers. The Brake cleaner, the Ant seize, the liquid tape, the diagnostics with multimeter, not breaking off the 'ears' of the bracket (using pliers). Keep up the great work!! None of it is boring to me. !!

[@EM-df6mo]

Eric O's Theoretical Mechanics Class and logistical repairs. This guy is the difference between a real technician, and a "parts replacer". Another complete repair.

[@greg6180]

You are my far the best mechanic on here. You positivity. Your attention to detail. You are down to earth and take the time to explain everything to us viewers

[@elcheapo5302]

I have never seen anyone else never seize an alternator bolt bushing hole. That's thorough!

[@recoveringnewyorker2243]

Hey Eric! Retired mechanic here. I now sell auto parts and hand out advice (or try to). We had a similar vehicle with a no charge condition. I instructed the owner to go home and remove the alternator and bring it in for testing.Our testing machine revealed that the alternator was just fine. I told him that the ECM was probably the problem (check engine light on for months) and to go home and reinstall the alternator and bring the vehicle back for testing.Sure enough, there was a no charge condition. The owner told me I was an idiot , we were all stupid, that our alternator testing machine was faulty and demanded that I sell him a new (remanufactured) alternator. I'm sure you can deduce what happened next. Thanks for putting out great videos! Respect and admiration sir!

[@Brindle_Boxer]

Hello Sir, may I borrow your experience? I’m not able to get a voltage reading while directly on the battery terminals (wires are hooked up). Same deal if I go from the jumping points. If I go from positive, to the ground that’s on the firewall, I get 12.5 or so, regardless of whether it’s running or not. I cleaned all terminals and ground connections that I could find. My next step is alternator. Is that a good assumption? It’s a 2000 GMC Sierra 1500 4WD 5.3L. I’m just a DIY guy, not a mechanic (obviously). Symptoms: battery light on dash is on. Truck died on the road today. Replaced battery and got it home. Battery light is still on, and my voltage readings are listed above.

[@r3dhorse]

@@Brindle_Boxer More than likely alternator but take it out and get it tested if unsure.

[@Brindle_Boxer]

r3dhorse You’re correct, it was the alternator. I have an old hand me down digital tester, and it was throwing me off. I borrowed another voltmeter and confirmed it was the alternator, and then replaced it. Thanks for replying!

[@norisboren5402]

@@Brindle_Boxer One of the 2 voltmeter wires is broken, it connected when reading gnd. on firewall . Also Eric said take alt. to parts store for test, if good then ck. that ECM is sending 400 hz. to alt. while motor is running .hope helps.

[@mrmotofy]

Always test your test equipment to rule out faulty test equipment

[@TheCowgirlNiamh]

Who the hell would thumbs down this?!! Can only be the parts guy after making 3 trips to SMA!

[@kevinday4474]

Agreed. Two thumbs down within minutes of posting a TWENTY-MIN video?

[@eddiemartinez265]

CANT BE he is playing with the cat if it is still alive.Jimmy S

[@eddiemartinez265]

Must be a nut that was a good video.Niamh Healy

[@TheCowgirlNiamh]

Three thumbs down now! One for every trip he made? Haha he's pissed! :p

[@eddiemartinez265]

Could be he may have been on his smart phone.

[@infidelzombie9382]

I had a newly licenced mechanic in our shop have this issue and he immediately went to parts for an alternator. I asked him his test results and he said it's obviously the alternator why waste time. I had to show him the testing procedure he had no idea how to do it. The ECU wasn't giving the signal to charge. He always follows procedure now and he's become a good analytical mechanic. Mechanics 101 young fellas watch this channel and learn from a pro

[@dalltex]

Keep bringing the "everyday stuff" because we learn stuff and it's cool watching you work.

[@XqeDiosxqe]

I love how you go above and beyond your work ethic. It's all in the details.

[@alientrade]

Man, oh man, this is an AWESOME video. Mike, you are a mechanic's mechanic. This is the best repair video I have ever seen in my 76 years. Thanks, loads. Barry

[@alientrade]

Sorry Eric, this comment was supposed to go to Mike Lauer's GM Alternator rebuild However, this takes nothing away from you, as you are fantastic also. I enjoy all your videos. Thanks, Barry

[@joshuadunton2476]

As an Advance Auto Parts employee just gotta say awesome choice in parts for this video! But in all seriousness, these videos are great and help me out immensely when i'm working on cars i'm not 100% sure on. Keep them coming and thank you for putting in the work creating this channel.

[@snakeskinproductions7500]

I run into this kind of thing all the time. Boss used to give me a hard time for taking a bit longer to diagnose correctly. He's a lot happier now seeing as he is saving money in the long run by not replacing good parts with shiny ones (lol). I have seen it way to many times. Nice to know I'm not the only one that thinks this way. Keep the great videos coming my friend.

[@SouthMainAuto]

if you don't test then it is nothing more than a big fat guess

[@mikemassegrafixshopmike]

as a fellow mechanic I learn something new from watching your vids can never be too old to learn thanks Eric o keep rolling

[@fieldsofomagh]

Great diagnostic video. Never thought to check the ecm control wire input on an alternator. Learn something new everyday. As you say, it's worth covering all options and when it becomes routine, there's no great hassle and no dreaded comebacks !! New alternator holding up well under load and another happy customer.

[@tonykilbourn7812]

Overlooked the bushing in hole one time...wallowed out the through bolt hole, wobble in alternator Slung belt and left me stranded...nice touch! Very critical!

[@testosteroneinc.3800]

Eric and Ivan are competing on who can crank out the most videos in a week. GOOD STUFF

[@lijoima]

Garrett Martin nyet

[@klwthe3rd]

Garrett Martin I I watched Ivan and I wasnt impressed. His videos are not the same as SMA. His style and explaination is so different. im staying here

[@eddiemartinez265]

Yes it is great no matter who comes out on top we win!Garrett Martin

[@eddiemartinez265]

Ivan is good and he makes his point give him a chance. Kenneth White

[@eddiemartinez265]

His wifes truck.

[@jimzivny1554]

Good video, keep'em coming! Simple or complicated, it's good to learn or refresh the memory, we all develop bad habits over the years.

[@sungn4512]

thanks Eric for walking us through basic trouble shooting a possible alternator replacement. Keep up the great work.

[@grapeknutz]

Thank you for your videos, I only wished that I had back in the day an instructor that could explane electrical like you do! Keep up the videos not only you are entertaining , but very educational.

[@williambell9068]

I love the fact you got the difference between a short and an open circuit, so many call everything a short.

[@facundofuentez582]

Watch all your videos Eric. I like your approach and your commentaries. Especially when you sometimes jump the gun but are quick to let us know. That shows to me that you always double check either by t/s or calling Ivan or Keith. Great shows you put on! Keep up the fantastic videos!

[@arthurfricchione8119]

Eric enjoy all your videos and your troubleshooting techniques. Always informative. Keep them coming.

[@joannparker3974]

Wish I could find a mechanic like you.

[@edomihic]

Hi Erick, seen some negative comments about you, well my friend ,i been watching your chanal. And let me tell you thank you ,i done some repairs on my car thanks to you, don't pay attention to the comments from loosers. Keep the good work Ed from California

[@richardgonzalez8941]

I learn by reputition, over and over again. Different cars, same trouble shooting steps, adventually seeing a pattern. I learn alot from your videos. How you think, what you look for, the details that you look for, the details that you do from the experience you have so I will not go the wrong road, or break a part . Thank you for the information.

[@garywaisner7393]

Always enjoy. Chasing grounds and repairing is what I have a hard time following. Just finding the wires looks confusing to me. But, you are the professional, that's why I watch.

[@gordonfreeman5434]

Thanks for being upfront about the vantage. Good video.

[@sneakysnake109]

Yes, another Eric O video!

[@e13c7r0nic]

I have a 2007 Suburban. Watch all GM/Chevy truck videos with special interest! Thank you for taking the time to make these videos. I became a Patreon last month :)

[@robanderson84]

Pretty neat, i had no idea about the ECM matterial you covered, but the visual graph with load reductions was helpful to get a picture of what is going on. Thanks for the explanation, I learn something in every video of yours! Also, the brake cleaner scene was amazing!

[@brandontscheschlog]

Great info on the vid. I subscribed to your channel because it is very informative on electrical issues. Thanks for contributing your time to make these videos

[@sassyguitars]

Like what you said about not replacing until you really check, Thats what we call integrity, Hats off to ya.

[@rjh2459]

Really enjoying the hard work you put into the videos.

[@jaywebb0113]

just wanted to say... since i enjoy your channel i dont skip the ads

[@Kamdaddypurp69]

its crazy that you look into all these extra things most mechanics would just throw in a new alternator and say ur good but it might not work love this channel

[@josephtucci3666]

I heard the click! It was louder than the voices in my head! Best of luck friend.

[@vetman98]

Great video. Thank you for all your time making these videos. Always learn something new

[@scflooring8658]

Any video from you is a great video thanks Eric! You are a great teacher and very entertaining

[@michael.sierra]

"Fuel efficient 6.0" I love your videos.

[@willb3598]

Keep doing what you're doing Eric O.!!!

[@heavylead1961]

that's why mrs o is so important to the shop!!! she orders the right parts lol ;-)

[@eddiemartinez265]

She sure is that's what they say behind every good man is a good women!

[@1wtrahan]

Well call me slap nuts , that’s right she wasn’t in that day boy boy boy stay in the shop my man you have a lot to learn 😂😂😂😂😂😂

[@billrimmer5596]

This video was very helpful for me on an 08 Torrent 3.4.

[@allcureman3403]

Once again. Great job Eric!

[@dil6969]

13:00 - In Knipex we trust!

[@treygarcia8264]

I like when you fail makes me want to keep pushing to get better. Brother you are teaching your replacement and that what we need to do. Boss up

[@Darjan_Spasojevic]

Alternator is at the top, like a mustang. Good job GM, you did something right

[@mr.nobody9630]

Only haters will give these video thumbs down. Two Thumb up for the SMA Channel

[@sargefreedom1578]

Always good to make sure. Nothing aggravates me as just throwing in a part to find out the issue was a broken wire or other problem

[@bradarmstrong3952]

Thanks for an informative and helpful video - the small stuff is important too!

[@CanadianCharlie64]

Great video as always Eric O

[@R.E.HILL_]

Another nice one. And Hannah still helping out. Thx for sharing.

[@ScottysDetailing]

Great video well done! You always do awesome! Videos just when I need them.

[@ulysees08]

Thanks for the video Eric. Enjoyed it👍

[@Geekdiymechanic]

Nice work. Thank you for the informative videos that you do.

[@adrian5401]

Great video and a great technician

[@comingundone27]

Brake clean. solves all problems. Love the entrance music for it! I hear it in my head when I grab my own can at work haha

[@manual6speed]

This topic reminds me of a charging system I looked at and repaired like 22 years ago. Drove someone to pick up a used mid 1980's ish GM sedan (cavalier/delta 88 I think) car they just purchased, as soon as they started it battery light was on (previous owner claimed to not know about it). Got the vehicle back to their residence (after several jumper cable charge and start sessions), pulled out my digital multimeter and ran some voltage checks. Key off had no voltage on heavy and medium red wires (alternator had the medium and small wires in a white connector on the side), with key on had voltage at the small wire. Knowing the large and medium wires were supposed to be always on, and medium wires usually routed to battery post on the alternator, i pulled out my jumper cables and made a direct connection between the battery positive and battery postin the alternator. Started the car and it started charging. After all that background I traced the large red cable to a set of fusible links at the battery post of the starter (of course the links for the alternator wires were blown). Repaired the links with suitable replacements and made the people happy that they could drive the car they just purchased.

[@richardbambenek2601]

This video closely replicates my reality when working on a car. Blame it on a brain cramp or brain fart or more likely in my case a senior moment.

[@johnnyinostroza5807]

Thanks for the videos,Im testing my daughters Cadillac CTS 2011,Battery light came on,I charged the battery,the car has a reader for the voltage it went up to 14.2 and running after a while down to 11.85v ,looking at all these videos looking for guidance and you impress me with your knowledge, even if you ordered the wrong part twice,😂 it takes a real man to admit his errors,anyone else would have deleted that. Great job. Hope I can find what is wrong,because this alternador is way down deep and under.

[@mrdropback7388]

Man these videos really help the average Joe like my self learn and save money thanks

[@mikep95133]

I found out my alternator is intermittent because I took my portable bench scope and looked at it's output. I hate guessing. So I don't. Great detail Eric !!

[@Paul1958R]

Eric, Another great video. Thanks and God bless. Paul

[@robertdonnamowrer6439]

Hello EricO thank you for making these videos . Just watched your 4part video on your 5.3 Chevy engine swap ...I hope that day never comes on my 03'Seirra....stay safe and have fun at work I ,I know every day is not not fun and games but I can tell you enjoy your job!! Just wondered if any " ladies " watch your videos that had their vehicles worked on at you shop and heard you say "Well there's you problem ,Lady!!" That cracks me up!!

[@SouthMainAuto]

Haha no but when they do I will be sure to use that line!

[@baxrok2.]

Very informative. Thanks!

[@Bmizzzle1]

12:30 the most beautiful sound of spring, the call of the robin.

[@dushk0]

they are chirping pretty much round-robin :)

[@joedorosh]

Never have I loved seeing brake cleaner so so much. :)

[@peterfrenzel1826]

Excellent amazing videos, I wish that I lived where you are so I could bring my vehicles to you. Outstanding troubleshooting before replacing anything. Also, like the videos with that little QT (Miss Hannah) lol Thanks for the videos, learned a lot.

[@korycevering1597]

Love the shows. Would you be willing to do a video on the diagnostic tool. That would be great to see and hear you opinion on functionality and what to look for.

[@mrkttrdr2919]

Another informative and entertaining one for the archives, 2 returned alternators is payback for all the bad parts they have sent u

[@SouthMainAuto]

I still feel bad about it, ihate making mistakes

[@mrkttrdr2919]

South Main Auto Repair that's why we keep watching, ur human and honest, thanks for being one of the best channels out there

[@dyardsale5475]

awesome video. Wished you had discussed what the other control wire does and how to test it.

[@brandonkahuna1251]

Great video Eric!

[@bertnovak952]

Because of the squeaky belt and while the alternator is off it would be a good idea to check the other accessories for rough bearings. I had an alternator replaced that wasn’t faulty but the water pump bearing was shot but not leak. That caused the squeaking and alternator not able to spin while the ECM was asking for full charge. A fan of your channel.

[@codywichman213]

Eric, Working as a full time mechanic I know the fight for the right part, and its a crappy deal! I can easily turn a 25 min job into a 3 hour jobs. Often the part is out of stock or unavailable. Unfortunately on a daily basis I deal with this crap that they call reman. Gotta love rediagnosing a new part as bad or defective. Most people don't understand the struggle and get upset when you suggest dealer parts for this reason.

[@Travelingman-1980]

Eric, shit happens with ordering parts, it makes for video drama anyway. Its great how you show us all the tests, I really get to learn from these examples, thanks.

[@chkr1610]

2am in AZ, well I was going to go to bed, haha. Awesome videos!

[@boboften9952]

Have you moved the you tube viewing screen to the sleeping room.

[@kylefowler5082]

This is an awesome video, I am just a DIY'er but bought a cheapo $40 oscilloscope from Amazon to test the questionable alternator on my 2004 chevy tahoe. It's good enough for broke people haha. However I really like the idea of buying a nice multimeter capable of reading Hz at 3v RMS and up. I have a nice Klein meter but apparently it can only read Hz and duty cycles at 8v rms and up. The duty cycle wire voltage on gm alternators of this vintage is 5v rms lol. So keep that in mind when multimeter shopping It felt great to definitely diagnose the problem before throwing a part at it and praying. Thanks for your help Eric!

[@63256325N]

It's all hunky dory! Thanks for the video.

[@angeljarquin5133]

You are the best eric no matter what !

[@christinehucklebridge1534]

great vid. I have a habit in a situation where re-using the old belt, of adding a small dab of dialectric grease on both sides of it.

[@SmittySmithsonite]

Playing catch up this morning - I'm way behind! On to the next SMA vid .... :)

[@donnierobertson3088]

Great job again like always A+

[@bthomas6381]

That bird singing in the background is great..!

[@thatsteveguy18]

Almost brought myself to donate a new belt and tensioner for this guy. I would go batty having to listen to that belt squeak all day

[@VIheavyequipment]

dude i pretty much enjoy any video you put up lol

[@SouthMainAuto]

Thanks Man!

[@20tea]

I had an alternator test good at a parts store with a 'low charge ' indicator on the dash 2007 yukon denali. Swapped it out with a new one with a 300amp output and fixed the problem.

[@jamesearl1756]

"I'm not one to shotgun a part at it. I'll just shotgun 3." Haha! Great video!

[@dougkubash8673]

On the old Delcotron alternators you could test them by going through the 'D' shaped hole on the back of the alternator case with a small screwdriver and touch the back of the regulator on the inside and touch the case and it would 'full field' the alternator.

[@dalandser562]

"It helps when you can pay attention and read." @17:30 - words of wisdom :)

[@haywardsautomotive6156]

HAHA Ordering wrong parts happens to the best of us. I've managed to do that enough times to make me laugh now but wasn't funny at the time but it makes getting the right part like Christmas! Nice diagnosis & video as usual.

[@SouthMainAuto]

Yeah but when a 30min in and alt. jobs turns in to 3 hrs it is not funny then haha

[@haywardsautomotive6156]

Yea that's why why I said it wasn't funny at the time & I am never happy when it happens and usually say a few choice words at myself just to calm me down but when you see someone else do it then it somehow makes you chuckle...thanks for the chuckle :D

[@haywardsautomotive6156]

If I made videos you'd be chuckling your ass off HAHA

[@b.r.3232]

Cool! Nicely done!

[@livalittle100]

Great video. good info.

[@2000cobraguy]

Eric: The GM V8's with the "small" 105 amp alternator can be swapped with the higher amp 145 amp alternator. Same connectors and mounts. The way to tell which you have is easy. If the front and back of the alternator case "touch" each other directly, you have the smaller 105 amp alternator (which this video shows) The larger 145 amp alt has a 3/4" "spacer" between the front and rear of the case. When upgrading, just replace the belt and get the one for the larger alternator. Also, the higher amp alternator is CHEAPER I have done this upgrade many times.

[@TheSmoochy2]

Good review. Love the snap on meter. Had a similar problem, but it was diode in alternator, Does Chevy have a plug in to check alternator while driving, or a dash add on device,? Bo

[@MegaHarobikes]

excellent video

[@videosgoneviral7858]

Awesome vids 👍👍

[@traumahawk517]

good info,thanks

[@petemiller5813]

Remember: if you're not doing anything you don't make any mistakes. Also, it's only a mistake if you do not learn from it.