Starter Circuit Voltage Drop

This video shows testing starter circuit voltage drop on a Toyota Pickup that would not crank.

[@Basslicks82]

Stumbled upon this video while searching for information on a 98 4runner with a "click, no crank" condition I'm trying to diagnose. I recognized that engine bay right away! Thanks for the video. I haven't done a voltage drop test on something in a couple years and needed the refresher.

[@FireicerCooper]

This is a brilliant example, thanks for sharing. You would have never have guessed it being where it was as that looks like a clean good connection. Proves looks can be deceiving.

[@luc5565]

Great job. It's a realistic real world application on voltage drop testing.

[@ttcautotech]

@Juusstas In the video we are using the direct method of measuring voltage drop. One lead is placed at the beginning of the circuit (B+ at battery) and the other is placed at the other end of the circuit (B+ at starter). Any voltage lost between the B+ and the starter B+ will show directly on the meter. We are not measuring voltage to the starter! Since both our meter leads are on the B+ circuit the meter will show the total voltage lost in the B+ circuit. We had 12v at batt but lost in circuit.

[@elijahchikuku9543]

one of the best practical examples I ve watched on -line.Thanks for sharing

[@kneedown4GOD]

great vid,you really simplify the voltage drop test.it sometimes takes time to wrap your head around it but once you do, voltage drop can really be a life saver.

[@TruthBomber]

Thanks for this video, I like how you didn't gloss over anything, but showed exactly where to probe for each different portion of the circuit. Very well explained. I was able to methodically pinpoint my problem area as the interface between ground wire and clamp. Put a new clamp on, cleaned the wire, and solved a very frustrating, intermittent problem. Thank you!

[@chadchristian3704]

Thank you for taking the time to create this video....very informative. Bottom line you quickly & effectively determined the problem without excess expense & labor. Interesting how voltage can drop so drastically from one connector to another. Keep up the good work

[@gsoup7850]

Im learning voltage drop at VW national learning centre in Milton Keynes England today, this video is fantastic and has given me a great head start, thanks a lot!

[@jschirr]

absolutely one of the best videos on voltage drop i have seen on youtube. great job!

[@DusterMtnEX]

I just want to say thanks for this video. I've spent days reading electrical mumbo jumbo trying to learn about this and other concepts of testing DC systems. I've learned more here in 6 minutes than I have learned in the last 6 days.... Now if I could just understand how I can have enough supply voltage to a good coil but not enough flow/current/amps to make a nice fat spark instead of a skinny orange spark....

[@gzimca]

Hvala majstore,odlicno obavljen posao. Sir,thank you so much,excellent video. Keep sending us more. Your accent is so charming,you sound like John Wayne-The Duke. Regards from serbian mechanic.

[@rrmech11]

Excellent job of explaining voltage drop

[@LeoJayawardena]

Dude that the best example of voltage drop test on the tube well done boys

[@turboflush]

Dude! Best and simplest video i have seen

[@ttcautotech]

Absolutely! I have to help techs who have been feed the fallacy that because the meter says there is voltage on a wire it must be good. They will unplug something, find voltage and declare the "power" good. Only to plug the component back in and find no voltage on the very same wire and not understand why? It requires a deeper understanding of the actual dynamics of electricity in the real world.

[@Glens1965]

This is a very good video. You explain the process very well. Thanks for posting this.

[@marcinmorris]

Thanks man. This is a video I was loking for ;) god bless you

[@RODALCO2007]

Great video , well explained and demonstrated.

[@mohammed.u]

Thank you very much, I am having similar problem with voltage drop from the alternator, this would help me very much diagnosing my issue.

[@stspringer2003]

The best video yet

[@bobtat]

Great vid guys! Not sure why voltage drop testing seems get some lost in the forest but your video should help them see the light...or volts. Thanks

[@TheSchlerm]

Great video! I learned a lot.

[@spelunkerd]

Nice to see an example of clear thinking, applied practical science.

[@Alekcanuk]

Thanks for making such a great video.

[@bobbobby472]

If a circuit is energized or powered, as a convention we say that the operative voltages exist even though there is no charge or current flowing and the voltages are theoretically infinite. This is in recognition that the energy or power is instantly accessible whenever a load is introduced into the circuit.

[@nsashby]

Great video. Well explained. Nice meter. Thanks!

[@GRUSSNewton]

Nice simple video! Thanks for sharing!

[@foreverwood1963]

Wow I'm stunned ! I would've thought the vehicle would start with 11.7 volts at least attempt to turn over. That post didn't really look bad either you just gotta do the test. I noticed that you were not initially on the clamp, that was good for me to see. Thanks

[@danielwoodhouse1870]

Really good explanation...thanks!

[@AutoTechHector]

@MrHvm1985 I couldn't agree with you more, There is a lot of voltage drop questions concerning the starting circuit in the Electrical ASE test. You wanna learn voltage drop... this is it right here!!!

[@bpure3338]

Great video!

[@LSDdreams808]

Fantastic job guys

[@bluebeltatt]

very good tutorial i use dielectric grease on just about every electrical circuit JUST to be safe .

[@jeremieadkins2858]

Very well done! No backtracking I would have tried the wires and initially missed the connector. Goes to show your eyes can only tell yoh what’s defiantly wrong. Not what looks ok.

[@bambino9553]

That was awesome guys👌🏾

[@jheetman]

great video, i drop test before checking voltage at accesories, much faster to find problems that way. just remember that the cicuit HAS TO BE LOADED to check the drop in voltage.

[@ozzstars_cars]

So after the repair (cleaning the wire connectors) the voltage drop at the starter terminal should be zero? Before the repair it was close to 12 volts. Is that right?

[@greygoosemafia]

Great video guys. god bless

[@gazzathegreat7820]

top marks i think i may have just found out whats up with my car or similar problem i will be filling you in

[@ttcautotech]

You must have looked that up in your middle school textbook. lol Finally you said something that made sense. "Voltage is.... amount of energy driving a charge at any point in a circuit" Again a meter measures potential at two spots. It doesn't mater if one is ground and the other is power or if they are both points on the power feed side of the circuit. As long as there is a difference in potential between those two points the meter will read it! Sounds like your facts are proving me right!

[@ttcautotech]

Bob, I hope we can continue this this discussion. The more we discuss this the more I feel we are not that far apart from agreeing. I feel the problem is not an understanding of electricity, but more a misunderstanding the dynamics of the circuit in the video.

[@Kirayagamiful]

Thanks man it's worked!!!

[@kennyhatcher6408]

Thank you great job!!!!!!!!

[@ttcautotech]

@mindswapp In the case of high current circuits like the starter, resistance can not be measured accurately enough with an ordinary meter. For example, .01 ohm sounds like a good connection. However, if the starter is operating at 150 amps this resistance would cause a loss of 1.5 volts! Think of it this way, resistance is a static measurement that tells us the circuit is there. It does not tell us how much current it can carry. Voltage drop is a dynamic and true test of the circuits operation

[@REDTEAM22003]

love for you guys

[@xexorz]

Excellent Video - Great diagnostic technique! For those who want to know more about the Maths, look up "Ohms Law" to learn about voltage drop across a resistor (which is what we have happening here - the bad connection is effectively a resistor (all-be-it a potentially intermittent one).

[@sirsweetness8332]

Very good video. Trying to help a friend who has new alternator and battery and can start the truck by jumping the starter but will not fire up without jumping it.

[@turboflush]

Sir Sweetness What did you find?

[@bobbobby472]

At this 3rd level of understanding, there are 2 competing but equally rigorous and correct systems for describing "electricity"; the 2 systems vary only by including or not including time as a factor. The system that does not include time is more fundamental, getting right down to the sub -atomic physics that drives electrical phenomena, so I prefer it. Let us call it FS for fundamental system. The popular le Systeme International includes time

[@Le_Comte_de_Monte_Felin]

At last! Someone instructing instead of showing off their infinite knowledge about electrons and flux capacitors

[@ttcautotech]

Well, I agree with the FS explanation you mentioned earlier. So maybe this is a misunderstanding of what was occurring in the video. It sounds like our understanding of electricity is similar, but that there is a lack of understanding about its application in the video.

[@theomnipresent1]

Good stuff!

[@ttcautotech]

Assuming you are talking about a circuit with no current flow you are correct. Voltage can exist without current flow. However current can not exist without voltage to drive it. Most of what you are saying applies to an open positive supply wire. In the automotive field measure voltage drop in this manner leads to misdiagnosis. While applicable in other fields it is seldom used.

[@ttcautotech]

Lets take the switch you mentioned. An open switch in the positive circuit will have 12v on one side and 0v on the other. Now close the switch. In a perfect connection you would have 12v on one side and 12v on the other. However the real world is rarely perfect and most switches will drop a small amount of voltage. For instance voltage on the inlet may be 12v and on the outlet may be 11.92v. You can take the before and after readings and subtract to get volt drop of .08v or.........

[@tspriggsabq]

That's cool. Even as an elec. tech with years of experience I never seen anyone do that. Pretty simple too. Imagine a large resistor which youre measuring across--and it shouldnt be there.

[@PineCreek4x4]

I wish all electrical repairs were this easy. Nice job though. Not many techs even know what a voltage drop test is...

[@ttcautotech]

In an automobile this "perfect" supply wire rarely exists and it doesn't have to. Some resistances in the supply circuit are acceptable as long as we have enough electrons to perform the work necessary. On the starter circuit the development of resistance is acceptable as long as the combined voltage dropped across them is less than .3 volts. Again for this voltage to drop the circuit must be complete. This is simply ohms law applied to a series circuit.

[@bobbobby472]

OK, what we've got here is information being expressed at different levels of understanding and usage. (1) An electrician only needs to know that his voltmeter measures something called "volts", without being concerned what "volts" means. If his voltmeter reads 117 volts here and 235 volts there, he knows whether or not the circuitry is working properly.

[@bobbobby472]

. Disable the engine so it will not start when it is cranked. (Ground the ignition coil wire, or disable the ignition circuit or fuel pump relay.) Limit cranking time to 15 seconds or less. C. While cranking the engine, record the volt reading on the DVM. D. Next, connect your meter positive (+) lead to the battery terminal stud on the starter, and the meter negative (-) lead to the starter housing. E. While cranking the engine, record the volt reading.

[@ttcautotech]

@scootbmx01 Ah yes. Voltage drop on the ground, while not the problem in our case, would cause the exact same symptoms. A bad connection on either could cause the starter to just click.

[@ttcautotech]

Well Bob, at least you've finally gotten the Math part right. Let me try to explain one last way you might understand. Voltage will not drop through a circuit that is not active! If its active and there is any resistance, voltage will drop anywhere there is unwanted resistance. If the circuit is not active it would be impossible for voltage to drop. We are checking the circuit when it is active!

[@ttcautotech]

Place one lead before the switch and one after the switch. The meter will show the difference in voltage between the two points: .08v. One lead is on 12 and the other lead is on 11.92v. The meter will read the diff in potential of those two points. One thing that may be puzzling you is that voltage only drops in a complete circuit. Just checking an unhooked bare wire will not work because no current is flowing. If you're still confused I can suggest a simple test with resistors and a battery.

[@ttcautotech]

I plugged in the drill, turned it on and moved apart the plug just enough to probe the leads again, and this time his meter read 56 volts! He was still dumbfounded. "It had to be the drill pulling down the voltage" "has to be". Much like you he refused to relent to the fact that he might not know something. Old habits die hard. Even after I showed him how to check voltage before, after, and ACROSS the melted wire nut in the cords junction box, he still thought something was wrong with my drill!

[@millionairefinesse5014]

Amazing

[@ttcautotech]

@vrbas100 My Serbian is not good. Are you saying there was an error?

[@ttcautotech]

We both agree! If you know this then why are you having trouble understanding the direct method of voltage drop. This is the basic theory behind it. Place a meter lead at each of those two different points and it will show the difference in potential/voltage You are being to sound like an intelligent person..

[@bobbobby472]

Set your DVM to the 20 volt scale, then connect meter positive (+) lead to battery positive (+) post (not the clamp or cable), and the meter negative (-) lead to battery negative (-) post.

[@ttcautotech]

Well, its not that its wrong. Its that we are using different terminology. If you think of electricity at its basic atomic level electrons flow from a source of potential to a source of lesser potential/polarity. Take a wire for example. It is impossible for there to be two different charges at opposite ends. A meter placed across the wire will not read any voltage. I think we can agree on this.

[@scootbmx01]

@ttcautotech i was just listening to the clicking sound, i had the exact same sound, grinded my negative post and clamp and it worked fine :)

[@ttcautotech]

On a vehicle, we want the power supply line to deliver electrons immediately to our load and deliver enough of them that the load can perform its purpose. This would be a properly working circuit. And if it was in great condition a meter lead place at two points in the power supply wire would read no difference in potential while the circuit is operating. Can we agree on this?

[@Nataliaa13B]

if it drops below 12.5v does that imply that the battery is the problem?

[@flylow2cre8u]

It's probably safe to assume that if you see a bunch of accessories hooked up to the batt, its bound to be cause of some concern later.

[@clcautotech]

Good job guys. I'm showing this to my students as a back up to my lecture and demo.

[@505197]

Volt drop tests are intresting, mainly due to the fact there is no "standard" . How many volts should I see drop between the alt and the battery? How many tenths is ok and at what point is it too high? I read .2 volts for a 70 amp output and kinda go by that as a standard. Resistance generates heat, how many bad cables have you found just by feeling a terminal? I saw a Japanese guy workin those multi-meter probes like they were chopsticks, man was I envious, he was precise as could be

[@anthonysandiego7082]

What settings in multimeter to put to check the voltage drop?

[@ttcautotech]

Leave the meter on voltage. Place the red lead at one point and the black lead at another in the circuit. If there is drop in the circuit, the meter will read the amount of drop. For example. Put the red lead at the wire going into a switch and the black lead at the wire coming out of the switch. If there is any voltage drop or difference in voltage at those two points the meter will read the difference.

[@ttcautotech]

however, no current is flowing in the circuit. Therefore no voltage can be dropped. I think we both agree on this. Now connect two different voltages to the wire. In theory, current will flow according to polarity until the voltages equalize. In the perfect wire this would happen almost instantaneously leaving no "time" to measure the difference in potential. I'm hoping we agree on this.

[@bobbobby472]

As charge (measured in Coulombs) moves through a circuit, it must be driven by energy (measured in Joules). Voltage (or Potential Difference) is a measure of the amount of energy driving the charge at any point in the circuit. Voltage = energy/charge = Joules/ Coulombs=Volts.

[@freshXtuna]

NiCE thanks :)

[@ttcautotech]

Well, because amperage draw would only tell us what we already know: something is wrong in the circuit, not locate the failure point. I hope that question was a stab at sarcasm not a lack of knowledge. A good volt drop a on a starter positive circuit is less than .3 volts. in this case we had almost 12 volts. And the indirect method of voltage drop does reference ground. The direct method I showed in the video is just faster. Could it be that now you are beginning to understand.

[@rusco321]

More automotive electrical videos. Thanks

[@bobbobby472]

If you reference your ground on ground the voltage drop will be read accurately if any exists, If you place both probes on a volt meter on positive, you wont/cant read anything, its 1 side or leg of power, it must be referenced to a opposite side of power, not itself, a battery wouldnt need 2 posts if this were true.

[@ttcautotech]

So you seem to agree that voltage drop can be measured that way: one lead on ground, one lead on various points in the circuit. If you find 13.6 volts at one point and 13.0 at another I think you would agree that the circuit has dropped .6 volts. What you don't understand is that placing the red lead at one of those points and the black at the other will cause the meter to read .6 volts.

[@bobbobby472]

So what does a voltmeter measure? FS explanation: As charge (measured in Coulombs) moves through a circuit, it must be driven by energy (measured in Joules). Voltage (or Potential Difference) is a measure of the amount of energy driving the charge at any point in the circuit. Voltage = energy/charge = Joules/ Coulombs=Volts. The voltage always has to be measured between 2 different points\polarity, in the circuit,

[@ttcautotech]

Well, I have to say that I have simplified this about as much as I can and you still don't have a clue. Although I don't think the problem is in the delivery of the information as much as it has no place to go.

[@bobbobby472]

A car starter pulling 150-200 amps for 15 seconds will sure drop your voltage from 13.6 to 12.6 easily and normally. Just reference power from both sides of power, the neg to positiive not pos to pos

[@ttcautotech]

@scootbmx01 Hmmm, did you actually watch the video? lol. Voltage drop is measuring the voltage difference between two points. ie. wherever you put your two leads. In this case the meter read 12volts. That meant that the difference in voltage between the clamp and attached eyelet was 12 volts! Since these two points are touching they should have exactly the same voltage. They did not! Notice it was the POSITIVE Clamp that had the voltage drop between the clamp and the eyelet..

[@ttcautotech]

An electrician was called to fix a drop cord in our shop. A drill would run at about half speed when plugged into the cord. The electrician comes in, unplugs the drill and measure voltage on the wires, finds 112 volts on the cord and says "cords good, its your drill. Even after showing him the properly running drill in another outlet he still insisted "its the drill" Why? because the meter told him so. Much like you he lacked a deeper understanding of the properties of voltage and current flow.

[@jimdavidson5208]

Nice video, now get rid of those crappy battery terminals. The wing nut type suck. Run a + and - buss bar for additional power taps. Not 5 ring terminals on one wing nut battery terminal. THIS caused the no starting issue. All you did was temporarily correct the issue. It will return. And why in the world would you recommend dielectric grease on battery terminals? You want the best connection possible.

[@bobbobby472]

OK, what we've got here is information being expressed at different levels of understanding and usage. (1) An electrician only needs to know that his voltmeter measures something called "volts", without being concerned what "volts" means. If his voltmeter reads 117 volts here and 235 volts there, he knows whether or not the circuitry is working properly. (2) A person reading a school textbook is going to be subjected to oversimplification, creative use of langauge and analogy

[@bobbobby472]

Look keping the negative probe from the voltmeters protocol, we all know that works read the batterys voltage, you need 2 sides lol it will not, cannot read 1 leg, if there was any reading its only due to line 2 /neutral being there as loads energized hello!

[@ttcautotech]

You just don't get that voltage drops as it is carried from the power source. If its a good circuit almost all the voltage makes it to the load. In a bad circuit some , most, or all of the voltage will drop before the load.

[@jimdavidson5208]

You need to troubleshoot from the battery TO the load. You jump to the starter awful fast. And never use those crap wingnut terminals. I've heard that some place before.

[@Thunderroad8517]

Wow. Tennessee is moving up in the world of You Tube. Git er Done . Tennessee Mike

[@ttcautotech]

You seem reluctant to consider that a perfect wire rarely if ever exists if one exists. Also, that this instantaneous (speed of light) current flow is of little use in the automotive world. We place loads in the circuit to control the the flow of current. Loads that benefit us in some way or perform work. We are not slowing the speed of the electrons, we are merely controlling how many will flow so our different potential points are not immediately equalized.

[@bobbobby472]

yes seems obvious, why not use ground as ground like normal? the volt drops going to be read from neg on battery the same way!

[@bobbobby472]

Whats the big deal, by not referencing the positive from the negative sides? Is it that hard to keep 1 probe(neg) on batterys neg post?? and referencing from neg like normal?, the meter wont read voltage until its energized, duh kinda hard reading voltage in a circuit de energized lol ,,and it says pos bat to pos stater lug reads zero which is correct, but says crank it and it will, only cause the other sides introduced lol

[@hddm3]

good diag

[@bobbobby472]

So what does a voltmeter measure? SI explanation:, same thing but with time The only difference between the two explanations, as I said, is a time factor. Power is the energy delivered per second of time. Current is the charge flowing per second of time. So when you compare Power and Current, it is mathematically and physically identical to comparing Energy and Charge. The time factors cancel out and you're left with only a language difference.

[@bobbobby472]

Whats the big deal not using neg to neg to test? why mess with moving both probes/ i clamp my neg and reference from there to all, accurately 34 yrs now lol

[@ttcautotech]

So, having to energize it "proves" it's reading both sides of power? So exactly how do you measure voltage? With the power off? If you are that's not a true representation of the actual voltage available to the load. And, if you had actually ever used a meter to measure anything, you would probably already know this.