How to perform a Starting System Voltage Drop Test

[@8rvanblarcom8]

So refreshing to find someone spreading good information that most people ( technicians ) don't even know. Bravo

[@rolandsmith2141]

My auto electrical skills are not very good videos like this are so appreciated and enjoyable, thanks mate

[@jessejameson154]

Brilliant presentation.....one of the best tutorials on KZbin regarding voltage drop on starting circuit.....and I've seen dozens at this stage

[@carlosdelossantos7212]

Señor I don't remember seeing that thermal imaging gun when I was in your Class. Very nice explanation. Being comfortable with the meter and understanding what test you're performing will help pinpoint the problem every time. Good stuff sir.

[@otowncolby]

This is easily the best demonstration and explanation of voltage drop that I've seen. Thank you!

[@chadh3441]

What a very detailed video! Great job and thank you for taking the time to share it! I've watched several videos dealing with voltage drop, but by far, this one is the most detailed and comprehensive yet. Cheers

[@MRDIAGNOSTECH]

Thank you

[@transmitterguy478]

Great video! I'm a Certified Electronic Tech and never thought to check my own truck for voltage drop on the starting sequence. Thanks.

[@randydavis7497]

Great video! one thing that was overlooked a bit. when you say “bypass the starting system”, it would have been great if you explained exactly how to do that. Most of us would not connect a lead to the fuse block unless we knew exactly what to do. Sure with you would have explained that part a bit better. But again, great video on voltage drop.

[@davidparker9676]

Takes me back to Trade Tech days. Very well demonstrated and explained. The FLIR camera really helps speed up diagnostics like this.

[@1231234abcab]

Very good explanation 👍🏽 The thermal imaging gun is a nice addition to the diag tools !

[@tonyt8314]

Great video!!! where do you get those large alligator clips for the test leads??

[@sirlancair]

Amazing explanation. I like that you dont assume we know anything, because I would have jumped to a different conclusion...until I followed along...and you helped me understand where i was going wrong. BTW, i had to sign in..and forgot my password, but i wanted to let you know and others, that this is an awesome video... I just got done making new battery cables on my twin inboard diesel boat. I suppose i could have found out the voltage drop at each terminal, and just changed the ones that were bad, had i known about your video. Thank you!!

[@itsmisterchris]

Man your video explains so well to a person who didnt know such test even existed , im excited to learn more n fix problems on vehicles ,

[@bwasman8409]

Very well done presentation! I've watch many that lose me through their's. Keep up the good work!

[@MukeshSingh-xy7cz]

Thanks for a flawless and finely explained video. Iam a electrical auto mechanic. I haven't come across such a video. Keep it up sir

[@MRDIAGNOSTECH]

Thank you very much. I'll keep uploading more videos more frequently.

[@danieljurgill1681]

The best visual on hands explanation I ever saw !!

[@lindakeiken2892]

I have never seen that tested like that . Very good way of doing that, thanks.ck,wisc.

[@jeffg1149]

Really should be attached to the post. If there was a poor connection at the battery this way would miss it

[@Mas7her]

I see your 177 meter does have a “peak” button which makes it easier instead of trying to watch for it.

[@MAZMSPBRA]

Amazing explanation!!! Straight and clear with the test procedure!

[@automaster209]

The only thing I would recommend is placing the negative lead on the bottom, or motor, terminal include the copper disc resistance in the solenoid.

[@bernardo121968]

I completely agree, but I don't think most people understand what you're saying.

[@LeverPhile]

​@@bernardo121968 Wouldn't you then see battery voltage (less the volt drop from the starter load itself) when testing between the M terminal to battery negative lead?

[@bernardo121968]

@@LeverPhile Read automaster209 comment again. It says he would recommend placing the voltmeter's negative lead on the motor terminal on the solenoid. So you'll have the voltmeter's positive lead on battery's positive post and voltmeter's negative lead on M terminal on starter solenoid. By doing this you will read total voltage drop on the positive side of the circuit while starter is cranking and battery voltage when starter isn't cranking.

[@LeverPhile]

@bernardo121968 Oh, this is for testing positive side? Ok, that makes sense then. I was confused and thought it was a comment on negative side testing. Thank you!

[@bobcote4893]

Excellent video. Thanks. It would also be helpful to show how you are cranking the engine.

[@jackburton2680]

I assumed a second person sitting in the driver's seat

[@bernardocisneros4402]

One end of the green jumper was connected to battery+ and he was touching terminal 87 of the starter relay base with the other end of the green jumper. Don't do this unless you know what you're doing because when you jump terminal 30 and 87 on the starter relay, you shouldn't turn the key to the "ON" position, because the engine will start when the starter cranks, unless you disable the fuel pump or fuel injectors and ignition. If you only disable the ignition, the fuel pump and fuel injectors will continue to work and dump fuel into the cylinders thereby flooding the engine.

[@earlsandersjr.2023]

I'm trying to get my degree in diesel mechanic technology. I'm taking electrical right now and what you explained in your video explains a lot to me regarding unwanted resistance. What is good and what's not. Thank you very much😊😊😊

[@gstranman9677]

As an old school diesel tech. I can tell you that you will be testing electrical circuits more than anything else on modern vehicles and equipment. Your main tools will be a scan tool and a multimeter while your wrenches gather dust lol.

[@radoslavnashev8345]

Love the way you repeat,makes me remmember it and hopefully level it up soon to get my van on the road .Thank you very helpfull ,top man! Best wishes Rad/Build4U

[@1b9e7n3z]

Very important and useful information for electromechanics, thanks for sharing.

[@John375PD]

Excellent tutorial!

[@ysitrim88]

Explained very well!

[@jackburton2680]

How do you do the first test if your starter won't crank the engine at all Should a failed attempt aka just turning the keys still energize the circuit suitably for this test?

[@bernardocisneros4402]

Yes, you can and should do this voltage drop test when your starter fails to crank when turning key to the "Start" position. Yes, a failed attempt will energize the circuit so you can do this test.

[@lupedelacruz4152]

If no crank start with checking your battery first and put a load test

[@rambleon2838]

What does determine the amount of voltage drop being acceptable?

[@MRDIAGNOSTECH]

Positive side: 0.500v Negative side: 0.200V

[@rambleon2838]

@@MRDIAGNOSTECH Is this manufacturer specific or in general for 12V systems? Thank you.

[@MRDIAGNOSTECH]

@rambleon2838 This are standard specs for electrical circuits.

[@sct911]

@@MRDIAGNOSTECH can the voltage drop tests be done with the car in a started running state? instead of cranking each time?

[@bernardo121968]

@@sct911 You're missing the whole point of doing voltage drop tests when cranking. Why would you want to do voltage drop testing on the starting circuit when the car is already running? In order to do a voltage drop test current needs to be flowing and current is not flowing in starter circuit while car is running. You can do a voltage drop test on the alternator circuit while car is running because current is flowing between alternator, car's electrical system, and battery.

[@shakeelsss]

Do you give one on one session on how to read wiring diagrams?

[@anthonyheak3479]

MR. DIAGNOSTECH, how did you cranked the engine from the fuse box? Nevermind, I think you had the key to the on position and jumped the starter relay terminal 30 and 87.

[@MRDIAGNOSTECH]

@@anthonyheak3479 by supplying voltage to the starter relay connector to terminal 87.

[@anthonyheak3479]

@@MRDIAGNOSTECH Thanks for replying, you did a great explaining step by step!

[@bernardocisneros4402]

When you jump terminal 30 and 87 on the starter relay, you shouldn't turn the key to the "ON" position, because the engine will start when the starter cranks, unless you disable the fuel pump or fuel injectors and ignition. If you only disable the ignition, the fuel pump and fuel injectors will continue to work and dump fuel into the cylinders thereby flooding the engine.

[@LearnItalianCVC]

What about battery voltage too low? I cannot pinpoint the source of the fault.

[@alwynventer77]

Great video Thank you. Helped a lot.

[@soudasuwa]

Extremely informative video!

[@cqmacht4513]

Great video thanks for sharing your knowledge with us, this is the best one I have seen on voltage drop.

[@huupham1025]

Great video! I wonder why you do not test the resistance so you do not have to crank the engine.

[@MRDIAGNOSTECH]

That's because it passed the resistance tets. A bad wire could still pass a resistance tets. The best reliable test is to perform a voltage drop test while current flows on any electrical circuit.

[@joehead1294]

The resistance is too low to measure. E=IxR For example 500 millivolts divided by 150 amps equals 3 milliohms. Or 150 amps times 3 milliohms equals 450 millivolts. But you need two of the three values to calculate. Not sure what the amp draw was in this test. I'm just using a value for the formula. Ohm's law.

[@bernardocisneros4402]

Voltage drop test are superior and more reliable than continuity tests.

[@bernardo121968]

@@joehead1294 No one cares about the actual ohm value of the resistance. You just want to make sure you don't have high resistance. If you get zero ohms or a few ohms for resistance, that's good enough. We're not trying to solve physics or engineering problems here.

[@joehead1294]

@@bernardo121968 Voltage drop is still the best test. Just saying very low resistance that you may not be able to measure can cause significant voltage drops in an operating circuit.

[@beakittelscherz5419]

This was very interesting, Sir! I will do this test to my scooter, bcits from 96' and I have some difficulties with the wiring. This will definitely help. And after watching a lot of videos about voltage drop, this one is by far the most informative so far! I will check out your channel and subscribe 🤓 Greetings from Germany 🇩🇪😎👍

[@stationaryenginesworldwide]

Great video sir ! Very well explained ..looking forward to more .

[@BritonAD]

I assume you're a mechanic. Can you recommend a Fluke meter that's good for autos?

[@westayers5174]

Fluke 88v or fluke 87v automotive multimeter is great tool for any electrical problems you could have. Really any fluke is great lol

[@BritonAD]

@@westayers5174 Awesome thanks.

[@cbarkwell1000]

EXCELLENT Voltage Drop Testing method...Your only MAJOR Fault is that you didn't tell the Public where both ends of the Green Jumper wire were connecting too to partially Crank the Engine.

[@bernardocisneros4402]

One end of the green jumper was connected to battery+ and he was touching terminal 87 of the starter relay base with the other end of the green jumper.

[@jessejameson154]

This would be a completely different video , and require a bit more expertise than ordinary diy. He would assume you could get someone to crank the engine. The process he uses should only be used by professionals , as it required bypassing the starter relay, as well as removing the fuel pump fuse. All cars are different as regards this , and any mistake could destroy the cars ecu ....so I'm not surprised he didn't show his process on this.

[@thegrandzenny3275]

Jumping b+ to terminal 87 on starter relay does not require removal of fuel pump fuse/relay. Only required when using the key to crank the engine. ​@@jessejameson154

[@ThunderbirdRocket]

That’s great ! Thanks for sharing this lesson with us !!

[@ritchieschofield1185]

That's a healthy battery!. Great video

[@lupedelacruz4152]

Very good amigo thanks for sharing

[@jordysandino6577]

Hello sir . Great video . When do you perform that test ? What’s is wrong with the car ? I’m trying to learn . Please forgive my ignorance

[@MRDIAGNOSTECH]

This test is performed on a vehicle that has a slow crank wich could be caused by weak battery, bad starter motor, or in this case unwanted resistance on wires and connections.

[@jordysandino6577]

Thank you so much sir . Please keep posting videos cuz we want to learn more about vehicles diagnostics

[@drazenaudi7864]

Svaka čast na jasnom objasnjenju....pozdrav iz Hrvatske.

[@jackburton2680]

Does the test work on an outright no-start situation due to a suspected bad starter?

[@MRDIAGNOSTECH]

@jordysandino6577 This test is performed when you have a slow crank condition and you suspect a possible bad starter motor, wiring, or engine. This test primarily check the condition of wires and connections for the starter motor circuit.

[@joelopez40oz23]

Did this vehicle have any symptoms? I noticed cranking sounds normal.

[@MRDIAGNOSTECH]

No symptoms because it had an 800CCA battery, strong enough to crank the engine without issues. This issue could cause a slow crank.

[@CesarCano-e7x]

You are confusing , the readings on the multimeter are 0.5 milivolts or volts ?

[@bernardocisneros4402]

The reading is 0.5 Volts which is equal to 500 mV

[@CesarCano-e7x]

@@bernardocisneros4402 thanks for the correction .

[@HighGrade_FireBlade]

You are 100% right. He kept saying the wrong thing. You aren’t misunderstanding anything, he just doesn’t understand what he’s saying. He’s saying “zero point five millivolts” which would be .0005 volts. He should be saying “zero point five volts” not millivolts.

[@danielpittman889]

Orale! Exactly what I needed to learn.

[@steelcamel5626]

are you located in a corrosive area???salwater?

[@8power0]

VERY GOOD EXAMPLE ,,, THANKS FOR YOUR TIME !!!!!!!!!!!!!!!!!!!!

[@thehighandgiddymast]

You can check the entire circuit by keeping the black lead of the multimeter at the negative battery post and the red terminal as a measuring device with a difference of .5 being the acceptable fluctuation value. You are confusing the issue by switching the leads at the battery post. No need for that....

[@MRDIAGNOSTECH]

@thehighandgiddymast That is called total voltage drop test, and it can be done on either the positive side or negative side. The purpose of this video was to isolate the main source of high voltage drop results.

[@thehighandgiddymast]

@@MRDIAGNOSTECH Absolutely. Thank you. Sorry for the trouble.

[@ShahzadShahzad-eo2ix]

Good example

[@Mako-sz4qr]

Fantastic man !

[@trygveseljeflot6245]

Forgot to test voltage drop over solenoid contacts ?

[@GL0697]

There was no need to, the TOTAL VOLTAGE DROP on the positive side was within specifications. If it wasn't then yes you are correct that would have to be one of the test points that should be checked.

[@bernardocisneros4402]

@@GL0697 No, he did not include both solenoid contacts when he performed voltage drop test on positive side. If he wanted to inlcude them, he would have to go from battery+ to the M terminal on the solenoid not the B terminal.

[@GL0697]

@@bernardocisneros4402 Please re-read what I wrote. There is no need to check those terminals separately, when the total is good.

[@bernardocisneros4402]

@@GL0697 I read what you wrote and there is a need to check the terminals. I've done this many times and if there isn't good contact between B terminal and M terminal inside of solenoid, you will not catch it if you only connect voltmeter leads from battery positive to B terminal on starter solenoid.

[@LearnItalianCVC]

Where are you located? Do you service?

[@bernardo121968]

kzbin.info/www/bejne/Z4S7ZoqNh7SgkK8si=vJy2zi3ZtsjRae8-

[@garylewis3641]

Very good video, enjoyed it!

[@ShahzadShahzad-eo2ix]

Very good explanation thanks

[@Charles_S.]

Very well explained 👍

[@s3nrdiz1904]

Thanks Mr.diagnostech ! Its like tryingto learn how to read . I DONT FN Get this !!!😖🤬

[@DavidGutierrez-zi4dy]

Great.

[@windward2818]

This repair is not easy because the chassis ground bolt connections will just eventually corrode again if you replace the battery negative cable. I have a wire line so I can make custom battery, starting, charging and power distribution cables. To save money I would not replace the battery negative terminal because it looks like it has a low side current shunt to measure return current to the battery, the cable will be pricey. I would use part of the existing battery negative cable about 5 inches and use a long barrel 2 or 1 AWG butt splice (Panduit), one side splicing the battery negative and a 4 AWG cable (to go to the chassis bolted connection next to the battery negative), and the other side a 2 AWG to go to the block (or transmission ground) for the starter and a 4 AWG cable (to go to the bolted connection at the frame below the battery). So, my barrel splice has four wires two on each end having a 2 AWG cable and a 4 AWG cable. This way starting current will flow directly from the battery to the starter case through the block ground and both the frame ground and the body ground (next to the battery) will have a return current path directly back to the battery. I would clean up the chassis and the frame ground connections before bolting the new eyelets. Then seal the bolted connections with NOCO NCP2. The original design is a bit puzzling because the distance between the frame and chassis grounds are so close together you would not use them for the starter. Just run a direct connection from the battery to the block ground and eliminate two bolted connections which we know will eventually corrode. Once this is done all we have to do is provide a frame and chassis cable back to the battery negative, of which a 4 AWG cable will be more than adequate.

[@mohammadbenattia9102]

Thank you

[@edwardreichard3852]

👍

[@johnstarks5323]

Good video, just a little too much redundant dialogue, other than that, great content.

[@nickayivor8432]

Welcome back, MR DIAGNOSTECH 👍 SHREWD, MR DIAGNOSTECH From Nick Ayivor from London England UK 🇬🇧 07:39AM Good Morning 🙏 🌄

[@naseembeg5396]

Nice video

[@glen._w_828]

I’ve seen loctite mess up grounding. People use loctite on starter motor bolts and alternator bolts instead just using correct torque specifications. Stop using loctite on everything

[@HighGrade_FireBlade]

You kept saying zero point five millivolts. That would be .0005 volts. The correct way to say it would be zero point five volts, or five hundred millivolts.

[@MRDIAGNOSTECH]

@HighGrade_FireBlade O.500V = five hundred millivolts. 0.050= fifty millivolts. 0.005= five millivolts.

[@HighGrade_FireBlade]

@@MRDIAGNOSTECH but you weren’t saying .500 volts. You were saying 0.5 millivolts. You had the decimal in the right place but you should have said volts. You are looking for a voltage drop of less than .5 volts or 500 millivolts. Idk where you got 0.5 millivolts from.

[@konstantin-big]

​@@HighGrade_FireBlade That's right At 4:37 that was 0.5 and he said 5 mvolt The right way to say is 0.5 volt that's 1/2-volt or 500 mvolt

[@rolandos64]

Voltage Drop = Potential Difference (Merely means, If you looked in your pockets, pulled out Your money, then emptied out Your Friends Pocket. What is the difference between Him and You. EX. You have $5.00. He Has $10 dollars. The Difference is $5.00. He Has $5.00 More than You.) under load on the same side!!! Its like testing a wire for continuity. Your DMM should read close to zero. You should see NO to little difference in Voltage/Pressure on one end vs the opposite End. Take Your $5.00 dollars from One Pocket, Place them in the opposite Pocket, youll Still have $5.00

[@JohnSmith-vt5ry]

Can you do voltage drop testing if the starter is not turning over (no crank)? When starting ignition (no crank) the voltage drop from (-) battery to starter housing is 78mv so good. My voltage drop from (+) battery to B-terminal jumps to OL. Its a new good starter. Starter relay is also good. The voltage drop from (+) battery to S lead is also OL when starting (no crank). ???

[@twosm0ker]

for a no crank you should confirm battery voltage at b term and confirm 12 v at the s term when trying to start.

[@bernardocisneros4402]

When your starter is not turning over, is exactly when you need to do voltage drop (VD) testing. If your readings from battery+ to B terminal and battery+ to S terminal jump to OL when you try to crank it by turning the key to the start position, then you either have a bad battery, a loose/bad/corroded connection at battery+, or very high resistance on cable going from battery+ to B terminal on starter solenoid and very high resistance on cable feeding power to fuse/relay box. The high resistance in these cables is usually caused by excessive corrosion but it can also be caused by physical damage. These are the only things it could be. Please share what it was when you fix it. It might help someone else on here.

[@JohnSmith-vt5ry]

Yes that is what it ended up being. Corroded bad splice that was on the power cable from years back. Took off the wrapping and there it was..

[@bernardocisneros4402]

@@JohnSmith-vt5ry Good to hear you found it. Thanks for posting. It helps others in the future.