Motor Age How2 #3: Using AC Coupling On Your Scope

Hooray! We finally get to capture a REAL voltage trace on our scope! And on top of that, we'll learn how to use AC coupling to eliminate the DC component to actually test the alternator's diode assembly.
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Due to factors beyond the control of Motor Age, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. Motor Age magazine (UBM Americas - Automotive Group) assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. Motor Age 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 Motor Age, 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 Motor Age magazine or its corporate parent, UBM Americas.

[@joemikos9155]

Thank you Pete, your videos have been a great help for me especially because you cover the fundamentals. I hade 6 ASE certifications which all lapsed in the 90s. I battled cancer for many years and put my wrenchs down over 20 years ago. About two years ago I was too sick, (and too broke due to med bills over $70k p/y) to change the power steering pump on my 88 Chevy pickup. I heard about a church that has a Car Care Ministry. Long story short, I got in for the church's once a month Car Care event and was quite shocked to see a huge, well equipped shop with 4 lifts and a front end machine. I did my best to hold wrenchs and pitch in with the volunteers working on my truck. I had been in bed virtually for ten years but it was exciting being in a shop again. Later on they rolled in 4 brand new tires. I hoped they weren't for me because I had no way to pay for them even though the tires on the truck were shot. Sure enough mounted them and put them on for me. When I told them I couldn't pay for the tires they told me not to worry about it! I was so grateful I started coming in as a volunteer. In the beginning I could only work a few minutes at a time. Eventually I got stronger, and started doing some real work. Now I do most of the diagnoses and pro level repairs. I have been able to get scanners and other tools donated by well known You Tube mechanics inspired by my story. I recently took in, on behalf of the Church a Snap On scope from the 80s called the Counselor I believe. Hey, a pattern is a pattern right? I have ultimately worked on hundreds of cars including dozens of donor cars. I didn't expect to be alive at this point let alone building a reputation and helping people keep their cars on the road. I now have a future at 60 and plan on getting my ASE L1 ultimately. Couldn't do it without the videos. Sorry for the long post but thought it might inspire someone to keep fighting even when there seems to be little or no hope. Thanks, Joe

[@Raylude5]

Joe Mikos Keep running the race brother. God bless you and bless the church ministry people as well. Good luck in the future on your L1😃👍

[@MotorAgeMagazine]

Thanks so much for sharing your story! I hope it inspires others to keep on fighting.

[@rrmech11]

Joe Mikos God Bless you

[@Spelter]

As an atheist I would say this should be a standard in a community and not bound to the church. But being a good person is not bound to a religion and or building. It's you, who do a good thing and help others. So keep it up and learn new things. Electrical works on a car has a traps but you need it. Look at south main auto, pine hollow, scanner danner and diagnosedan also, they show you a few things and basics that made your life easier.

[@carguy1312]

I’ve used it before, but never understood that a/c coupling was a fancy way of saying that you’re simply focusing on the a/c current. Thank you - SO helpful!

[@mike-yp1uk]

Thanks i really enjoy the back to basic tests because it just solidifies the power of the scope. Pro's need this constant training to get the accuracy needed for todays cars.

[@MandrewP]

Gawd, I love the scope!

[@donniehayes9419]

Thanks Pete for taking the time to share this info in terms easy to understand. I have learned so much watching you over the years and look forward to learning more the most important lesson I learnt is you can never get to much, when we stop learning it is time to change fields because cars are always changing.

[@MotorAgeMagazine]

Thanks for taking the time to comment Donnie!

[@rrmech11]

nice refresher

[@omareid8166]

I love this channel please continue in explaining scope for us until we become good at it Thanks again

[@mikepagan6300]

Thanks for clearing that up

[@tgoodm1]

Great information!!! Please keep these videos coming on using the scope. I'm an aspiring tech. Thanks!!!

[@MotorAgeMagazine]

Thanks for letting us know that you're finding them helpful. We have a lot more planned!

[@henryrobinson9837]

these videos are good for the older techs too like me (55) ,just trying to learn the oscilloscope,done it for 40 years but they is always learning involved

[@101numlock]

Thank you for taking the time to make these videos. I am sure that most of the entry level techs have snap on scopes vs Pico ! I myself am new to the snap on versus and really appreciate any training I can get on it ! Keep the training coming !

[@MotorAgeMagazine]

Thanks for sharing your comments!

[@davesministry7789]

Good video again Pete. You are an excellent teacher. You where the first video I watched after purchasing two of your DVD,s on how to operate the OTC EVO. There was, I think no avaialable information on it. The owner,s manual assumed you new the terms they where using. You explain these term,s Thank you.

[@MotorAgeMagazine]

Thanks for sharing your comments, daveS...much appreciated.

[@kevanpitt8614]

Thank you for take time make these videos for the entry level techs.I have a snap on vantage pro like to no how to use it. And get the best out of my two change scope! can for the next videos.

[@MotorAgeMagazine]

Thanks for taking the time to share your comments!

[@richardmcwhirter9396]

great video thanks it really helps.sometimes we need to go back to the basics to relearn

[@MotorAgeMagazine]

Thanks for taking the time to share your comments.

[@mugsymydog]

Pete ....I have the old version Snap on Modis with the 4 channel lab scope I am not able to get the same wave form you are getting. Is the Snap on veras a different lab scope then the one in the modis ?

[@MotorAgeMagazine]

Not sure. But nearly every scope I've ever used has had the ability to read AC alone. Try selecting an ACV scaling rather than DCV is you don't see the coupling feature as a standalone. Set range to .5v per division. Hope this helps.

[@REPOOCNITSUJ]

Another great video! When you are hooking up the leads, and you say "hook up the other leads to the battery" (approx 6:45), are you connecting the green lead into channel #2 and the ground to the yellow lead? or just using the yellow lead?

[@MotorAgeMagazine]

On the Verus, Channel 1 supplies the ground for all 4 channels. After connecting the yellow lead to the scope, attach the other end of the yellow lead to the positive side of the battery and the black lead to the negative post of the battery. If you need to use additional channels, you'll ground them through the ground you already have with channel 1. Make sense? REPLY

[@REPOOCNITSUJ]

Yes. Thanks for always replying. I just couldn't see the lead hook up from the camera angle. I just got a Modis a few months ago and I'm going down the playlist. 2018 is the year of the scope for me!! Thanks a million.

[@jasonc.4683]

Hey Pete with using the ac ripple test at the battery like u showed. What if u have excessive ripple. U would suggest replacing the alternator right away because plenty u cant reach ur leads down to the alternator post to do direct testing. U da man Pete

[@MotorAgeMagazine]

If you're seeing excessive ripple, the diode pack has failed and the alternator has to be replaced.

[@jasonc.4683]

@@MotorAgeMagazine thanx Pete. I just got my verus pro 2 weeks ago and I'm just playing around on known good cars to get familiar with the signals and get quicker at setting up my scope so it can become second nature. I have a uscope but I'm limited but it does wonders when u wanna connect fast and get a good idea before u have to break out the big gunz. Got alot of accessories from aeswave. Love the pico COP probe. Thanx Pete. Any upcoming classes u doing with TST back in jersey at union Blvd?

[@MotorAgeMagazine]

@@jasonc.4683 None planned at the moment...tell G you want me back...😉

[@ronaldamodeo4567]

Excellent choice in scopes. I have used a PC base scope and a few others but I love my verus. Pete what is your preferred go to scope? Enjoying the segments..

[@MotorAgeMagazine]

I've been a Pico guy for a number of years after cutting my teeth on an old UEI handheld 2-channel. Scopes have come a long way since then and there are several great choices out there now.

[@autonerdz]

Hey Pete. Gee... how did you get to be a Pico guy anyway. ;-) Good demo of AC coupling use. As you know, this isn't really needed using a Pico because of the powerful zoom features.

[@MotorAgeMagazine]

Yes, it's true! Before I came to the magazine fulltime, I was the East Coast rep for you guys. Kudos to all the great video and training content you make available to the industry.

[@autonerdz]

AC/DC coupling is one of the most misunderstood scope settings. Much of this is due to there being a lot of misinformation out there presented in classes as well as in publications. This leads many to think they need to use AC coupling for things like VR style sensors but that is exactly what you do not want to use. You did good... ;-)

[@ronaldamodeo4567]

What part of the east coast? Who were you a rep for?

[@Carlitosway211]

What is an acceptable range for the AC ripple? Is it less than 1v or 2v?

[@MotorAgeMagazine]

Generally, anything over 0.5 v peak to peak is unacceptable

[@Carlitosway211]

@@MotorAgeMagazine Thanks! I must not be doing something correct. Verus Edge set up just as it is in the video and I'm getting peak to peak of over 4v on multiple vehicles that have no electrical issues. Hope there's nothing wrong with my machine.

[@MotorAgeMagazine]

@@Carlitosway211 What time base are you using?

[@akaitv6606]

What's a cheap scope for a back yard mechanic

[@MotorAgeMagazine]

The AES UScope is a single channel scope with a lot of power for the cost.