Motor Age How2 #11 - Performing Relative Compression Without An Amp Clamp

Don't have a high amp clamp for your scope? No problem - you can still perform a relative compression test using this method. Pete explores the possibilities in this edition of How2.

Be sure and SUBSCRIBE to our channel so you'll be the first to know when new information is available!

@@@ FOLLOW US ON @@@

VISIT OUR WEBSITE!

TRAINING FOR PROFESSIONAL TECHNICIANS!

Click this link to subscribe to the print or digital edition of Motor Age!

@@@@@@@@@@@@@@@@@

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.

[padraiggalvin]

Thanks for this great video. I, ve just bought a scope last year and other test equipment and wasnt looking forward to spending more on an amp clamp at this moment.

[MaicSalazarDiagnostics]

This is great info Pete, this would be very helpful when checking a car out off the shop, I have been there with no amp clamp! Thx for sharing this.

[joemikos]

Great job Pete! I look forward to your videos and you never fail to deliver.

[mike-ypuk]

Short and sweet. Tools for our tool box. Thanks Pete for all your help.👍

[efanclublolsmaforlife]

Low amp clamp .. yes set to 60 amps an use your voltage setting on a 2 voltage scale that will read 200 amps will work

[sanratb]

Great teaching skills, thanks for sharing what only study and experience can provide. Greatly appreciate the

[nickayivor]

Good Evening Pete Meier motor age Take care and have a great day Pete Meier
Great tutorial thank you 👍
From Nick Ayivor from London England UK 🇬🇧

[billyr]

AC Coupled ! Nice ! That is ingenious !

[rogerh]

Hate to say it but I have used this method for quite sometime,  A change in currant results in an opposite change in voltage, As long as you have a scope that is fast enough to catch it. there are other test that can be performed using this method I will let you discuss these in future videos. Great information Pete I appreciate time and effort that you put into your videos on behalf of all of the professional technicians "Thank You!"

[nandor]

I use a low amp clamp on the 60 amp scale and set up as a probe on a 2 volt scale all the time to do relative compression test.

[vincebauer]

I found out if u have a new starter helps too u will get a great pattern I use low amp clamp on my 98. town and country and got the best pattern on my modus ultra

[bleebleblahble]

Fantastic video, Pete. I’ve learned a lot from you and the channel. Thank you!

[mike-ypuk]

For the longest time i used a low amp clamp set 2 volts at 2 seconds 60 amp ac coupled. The cables that are too big i would install a cable that i made 1 foot long and put it inline. Then i broke down and bought a high amp clamp. Scanner danner teaches the low amp clamp method. Great video i never knew about the low voltage method. One more tool for the tool box.

[richardmcwhirter]

Great info and explanation once again, Thanks Pete

[cwj]

Excellent video. Minor point - the first still photo of the BOB shows the meter leads reversed just as in the second still photo of the BOB where you point out that the leads are reversed.

[kasapis]

great information thanks for the great videos you have done . you have enough information on your scope to work out the engine speed on crank this is very importing information that some modern engines will not start if the crank speed is not right more then 200 RPM . may be you should do a update and show us out to work it out it very easy . but I let you show us how to work it out .   just only last week I was asked to diagnose a car that was hard to start with the ECU light on with a crank angle sensor code  this car had already had two new crank sensor but was still very hard start so I did the same test your doing in your great videos and  work out its was only cranking  at  140 rpm with a new battery and no voltage drop ( will there always some but it was ok ) to the started cables or the ground but with test I could see the starter motor had almost 500 amp and was very noisy that was interfering with the inductive crank sensor ! so this 5 min test I found out this car just needed a starter  motor and the crank sensor was ok . so working out the speed of the engine with this test is very important

[albertsautodiagnosticsllc]

Say your using a snap on verus edge instead of swapping polarity could you just use the invert waveform feature 🤔

[xylonify]

Hello, Pete. Would you recommend an Amp clamp with a multimeter? I have never seen you use one?

[petar]

Could this method be used to measure Fuel Injector Current draw at the wire of the injector?

[vieczurable]

I am a bit confused. Should I simply hook my scope on battery terminals for a voltage change measurement or AC Coupling is something special?