Mastering Diagnostics #13: Voltage Drop- The circuit stress test

[@Cakepillows]

Also good to know that the internal resistance of a quality DVOM is roughly 10M ohms. By connecting the DVOM in series to measure voltage the technician inadvertently put a massive resistance into the circuit. Resistance consumes voltages, and the largest resistance in a series circuit will consume the most voltage. Which is why the DVOM reads 12v or near source voltage. Voltage should be measured in parallel with a loaded circuit like you said. Great video!

[@MotorAgeMagazine]

Thank you for watching !

[@cjmazdatech]

I've got several test lights of varying draw for just such occasions from quarter amp to 4 amp, all tested and labeled with their draw on them and a bunch with banana jack ends. Great video as always!

[@brandonsteckler3417]

Awesome, thank you!

[@peacepoet1947]

A fuse or relay was bad. I had a bad relay on my 94 GMC. A few months later I had to replace the fuel pump. The mechanic didn't seal the gasket on the gas tank and the vehicle failed to the smog test. I personally dropped the gas tank and put in a new fuel pump assembly unit. The engine needed an O2 sensor. No code was shown on the code reader. 😅 I was very happy to finally pass the California smog test.

[@ThunderbirdRocket]

Very satisfying feeling solving the problem and saving money !

[@sheerwillsurvival2064]

Keep these coming helps the old guy get back into it

[@brandonsteckler3417]

You got it!

[@ThunderbirdRocket]

Nice 👍🏼 call ! Seriously !! I hope so too !!! 🎯

[@ThunderbirdRocket]

Valuable topic ! Great presentation Brandon !! Crystal clear coaching , no bs , trade secrets handed out !!! Love it . Thanks mate . 👊🏼 🔥 🏹 🎯 Voltage Drop Testing for the win !!

[@brandonsteckler3417]

Thank you!

[@petar443]

You're the best Mr. Steckler. 11:35 Thanks to this explanation now i fully understand why i changed 4 electric fuel pump motors on a Toyota and each new one was failing within a month(even an OEM one). This was 7-8 years ago. I remember i received incomplete/half the answer from Mr. spelunkerd who also have a youtube channel, but now i got the complete answer from you. Thanks. And the problem was - because i was changing the electric motor only (some fuel pump units , give you the chance to change the electric motor only) , not the whole "fuel pump module/sender unit" i found my voltage drop was on the wires inside the sender unit. You know the wires that are inside the sender unit and connect to the electric motor itself and also the fuel gauge float sensor. Back then i actually knew pretty good about voltage drop and circuit load testing. So i used 9006 bulb to load test the circuit at the fuel pump connector. Not only that , but i voltage drop tested it with multimeter while the light was glowing bright. But as i said - latter i found the voltage drop was on the wires inside the module..So the 5th time i replaced the whole module/unit and problem was gone.

[@brandonsteckler3417]

Yes! My point, exactly! 🤜🏻🤛🏻

[@vicpetrishak7705]

An old round Stewart Warner ampere gauge from live current to ground reading . Short time testing before burning a fuse and also checking grounding with current and the ampere gage . Thank You , very informative !

[@ThunderbirdRocket]

Love the old school well made equipment .

[@imfloridano5448]

Yep keeping your skills updated is always a great benefit to yourself and others you choose to help

[@MotorAgeMagazine]

My thoughts, exactly!

[@DJ-tn7vj]

Excellent video Brandon

[@brandonsteckler3417]

Thank you!

[@spirokattan3655]

Great info. Great series. Thank you Brandon!!

[@brandonsteckler3417]

Thank you, Spiro!

[@luismartinez1824]

Great presentation Brandon.

[@MotorAgeMagazine]

Thank You!

[@anthonysova7117]

Voltage drop for the win Yes sir VD=IxR turn the circuit ON Great presentation BRANDON Counter EMF adds resistance decreases amp draw CHEERS thanks for your demonstration

[@brandonsteckler3417]

Thank you!

[@HilarioScheid]

The first thing I teach in my course of Automotive Mechatronis is to show what a circuit really is, what are the variables involved and what are de relantionships among these variables. And I begin the explanation using a hidraulic circuit, wich is the best way to make them understand how it works.

[@nickayivor8432]

Outstanding tutorial ,BRANDON STECKLER MOTOR AGE 👍 QUICK-WITTED, BRANDON STECKLER MOTOR AGE Can't wait for the next training video My mentor,BRANDON STECKLER MOTOR AGE From Nick Ayivor from London England UK 🇬🇧 ⏰️ 21:34PM Good Evening

[@nickayivor8432]

Quick Ending Please do part 2 SHREWD, BRANDON Steckler Motor Age

[@joserodriguez2632]

Escellent presentation Brandon,I just learned something new.you see your videos are among the best in you tube.please keep them comming.God bless you.

[@MotorAgeMagazine]

Thanks so much!

[@7minnow]

GREAT JOB!!!!! Brandon

[@brandonsteckler3417]

Thank you!

[@DTEAuto]

Thanks for the good lesson and reminder!

[@brandonsteckler3417]

Thanks for watching!

[@gadasavideos8564]

Exactly same problem with a riding mower starting solenoid. 12v on the activation lead but not enough current. Bad connection at keyswitch

[@ThunderbirdRocket]

Good 👍🏼 find . Thanks for letting us in on the fix you did .

[@oddlurva7641]

Thanks for this Åge. Well first I don't understand anything?? Just kidding haha . I got a little lost today too. Now understand why the Fiat 500 is not used to haul large loads of timber. Many thanks to you Åge😁

[@robertmobileman8304]

Nice one Brandon , goid job

[@brandonsteckler3417]

Thank you!

[@raviautoscanning]

Great explanation. Thank you

[@brandonsteckler3417]

Thank you!

[@brianwalk108]

Here’s a fun one, for 20 years I checked fuses with an ohmmeter. No resistance = good fuse, right? Wrong. I had a fuse with 0 ohms but when checking it for voltage, one leg had 12.6V the other leg had 5.8V. Fuse looked fine, had continuity, but couldn’t carry any current! This fuse would have fooled an LED test light as well.

[@bernardocisneros4402]

1 in a million but it does happen.

[@brandonsteckler3417]

Spot-on!

[@PaulMorton-y6h]

Excellent Video! Just a suggestion, might also include how to diagnose if the resistance was in the ground side of the load (fuel pump). I've dealt with that too. Much less common but same outcome, insufficient voltage at the pump. Simply move the black lead to the battery ground and see if the meter reading changes.... yes there will be a small amount of difference due to the connections but should be very close if the ground is good. On the contrary, big change = resistance on the ground side of the load.

[@MotorAgeMagazine]

Yes, the voltage drop test can performed anywhere in the circuit, until fault is located. Whether it’s before the load, after the load, or the load itself

[@tedlahm5740]

The loads are in SERIES. Voltage drop will equal total voltage source. In series circuit CURRENT is equal thru-out the entire circuit voltage drop DIFFERENT at each load depending on residents. Kirchhoff’s voltage law, series circuits. comment please

[@brandonsteckler3417]

You got it!

[@ThunderbirdRocket]

Thanks for sharing this information .

[@mikechiodetti4482]

Good info, and it works.

[@brandonsteckler3417]

🤜🏻🤛🏻thanks!

[@secretsquirrel9722]

I know it's not the point of the lesson. But what was the fault? Burnt relay contact? Thanks for the knowledge Brandon!

[@brandonsteckler3417]

There was voltage drop in the fuse box (spread terminal).

[@crasher88]

Brandon two questions for you at the 13 minuter mark you were discussing how unwanted resistance before the fuel pump will cause a reduced ammount of avaliable voltage to the pump. you say that reduced voltage will cause the fuel pump to be damaged, how? what is happening in the pump that would cause the damage. i was always thought to substitute the load with a comparable test light to stress the circuit. my question is how do you know what size light to install in the circuit. you can measure the resistance of the good or look it up on service data but that is not always a reliable way to come to that answer.

[@brandonsteckler3417]

Great questions… When a pump isn’t supplied properly, it spins slower. The lack of rotational speed allows the brushes/commutator to burn (over time), because the current flowing through the brushes produces heat. A normal functioning pump spins faster and creates counter-voltage, reducing the heat across the brushes. I use the fuse as a clue to indicate expected pump current load. Circuits are usually protected to approximately 2x the circuit load.

[@trevorc1285]

@@brandonsteckler3417 how would this work when there’s several components on one fuse? Would it still be half of the circuit amp?

[@brandonsteckler3417]

@@trevorc1285, I’m happy to answer your question, but can you elaborate a bit more. I’m not quite sure I understand fully.

[@knock904]

good lesson brian

[@MotorAgeMagazine]

Thank You!

[@JaySosaNY]

How much voltage should drop on a loaded circuit? Testing just wires no connectors starts at 12.7 drops to 11.12 lights a headlight bulb bring im thinking i have a pin fit issue between bcm and sensor auto lights dont work

[@MotorAgeMagazine]

Although this is a great question the answer depends on a couple of factors: -how much current is flowing and how large are the wires (diameter). A perfectly healthy circuit will yield excessive voltage drop if the circuit is carrying more current than intended (for example: energizing a headlamp Bulb with #22 gauge wire).

[@romanjaspe4172]

Thanks

[@MotorAgeMagazine]

Thank you!

[@jharrison6557]

Brandon what are your thoughts on the LoadPro test leads in situations like what youre describing in the video?

[@MotorAgeMagazine]

Great question! Brandon feels the LoadPRO leads do exactly what they describe. He doesn’t own a pair but have used them several times. In Brandon’s opinion, he doesn’t feel they are necessary but certainly do the job they intend to do. His advice is: If you decide to invest in them, be sure you fully understand their limitations.

[@swav100]

What about a "loadpro" or are you against it like eric o or ivan

[@brandonsteckler3417]

My opinion only…. Devices like that take a simple concept and make it confusing for me. I prefer to load-test the circuit as I described. That said, devices like that work as designed, but they indeed have limitations (like everything else). And, if you are not sure of those limitations, you will make a mistake.

[@playharder1435]

Honda tech could have also "Ohm" tested the primary winding on the pump before replacing.

[@brandonsteckler3417]

Not necessarily…when resistance is out of range an issue is present. However, resistance is a static test and may not reveal the fault until the system is loaded. This is why the voltage-drop test saved the day

[@playharder1435]

Understood. An open in the pump's primary could quickly make the pump a suspect (before replacing) is what I meant.

[@SEDHACARREPAIR]

Morning sir Missing part 2 Video not full

[@brandonsteckler3417]

There is no “part 2”. I’m sorry but I’m not sure of what you are referencing.

[@SEDHACARREPAIR]

@@brandonsteckler3417 IMPORTANT I checked 4 times now All your other videos ended saying goodbye and finished properly This one doesn't Please check the VIDEO end at your earliest convenience. Sorry to bother you I understand the whole point anyhow Will put a sticker on my test light now to remember YOUR VIDEO. LOAD TESTING AT THE CONNECTOR NEED TO BE DONE WITH THE LOAD OF SAME RESISTANCE VALUE. FOR THAT I WOULD NEED A VARIABLE RESISTOR THAT I WILL CHECK THE RESISTANCE WITH THE MULTIMETER BEFORE THE PUT IT ON THE CONNECTOR FOR A LITTLE WHILE. AND WILL WATCH FOR THE CURRENT THROUGH FUSE BUDDY OF LIMIT.

[@brandonsteckler3417]

Thank you, I will get this sorted

[@MotorAgeMagazine]

Apologies for the glitch. We have made a correction in the description to reflect the missing portion of the video

[@sheerwillsurvival2064]

Wait what Hondas need fixing 😉

[@brandonsteckler3417]

🤣

[@ThunderbirdRocket]

Ha ! 😀. Yeah Hondas are pretty good 👍🏼 ! They usually run as smooth as sewing machines !! ✅ . But be at the ready . 👊🏼

[@derekmoult238]

As an aircraft electrician I always do at least 2 tests. Check for voltage AND test pump resistance. Takes seconds and confirms everything...