Should I Make a Bunch of Different Test Lights to Load Circuits?
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- เผยแพร่เมื่อ 16 ต.ค. 2024
- There seems to be a current trend, where a tech feels it is necessary to carry around a bunch of different homemade test lights. Each one carrying a different amount of current.
This is done in order to load the circuit, to test wiring integrity, when an open in a component is found, or because they may not trust their voltmeter and what it is telling them (unfortunatley most techs fall in this catagory).
While I like the idea, and will use my test light in this way, I don't need a bunch of different test lights, that carry varying amounts of current, to be 100% accurate on my calls. Just my 200ma incandescent and my 13 ma LED is all I need. Learn to trust your meter, combine voltage measurements with current measurements and use your test light at times to back it up. Are there times that having that high current bulb can help you? Of course! Again, my arguement is to those who would say it is NECESSARY to be 100% accurate. Helpful is one thing, necessary is another.
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![Voltage Drop Testing with a Test Light? [Part 1]](http://i.ytimg.com/vi/kTW68s5vqIg/mqdefault.jpg)
Good points, as usual, Paul. Most of us watch both you and Eric O, and I have a lot to learn from both. One of the compelling things about Eric's workflow is how quick and simple it is. For a fuel pump, he'll use a 4A test light at the fuel pump connector, with one side attached to the ground of the connector and the other attached to power at the connector. If a 4A test light glows bright, he has instantly load tested both the ground and the power side of the circuit, and he's done within a minute. It's hard to be faster and more comprehensive than that. He doesn't need to make excuses for why he doesn't need to load test the wiring, because it's already done. He doesn't even need to do voltage checks at the pump so it's no extra effort or time. You're right, if you measure a static 12V on one side and 0 volts on the other while loading the circuit, the pump has to be open. That takes just as long, and maybe you'll add a test light at some point of that algorithm, too. Not faster, especially if the tests point to a wiring problem. What if you get 10 volts? The attractive thing about loading the circuit with the current it normally takes is not only speedy work flow but also the reduction in false negatives and false positives. Some corroded connections may conduct well with low current flow but do badly when current heats up a tenuous corroded connection. That's the thing I didn't like about the LoadPro. We assumed a voltage drop of less than a volt was probably OK, but we were testing with much lower current than the device may normally use.
Good to see you, man! Have a blessed rest of your night.
I always check or substitute grounds first. Quick and easy. The older it is, the more common ground problems are in my trade.
I also have a load test rig I use if voltage or continuity isn't getting it.. It is just an aftermarket taillight pigtail that I can change wattage bulbs, as well as voltage, to mimic the load and pin or clamp in and move down the system until you locate the problem.I use this mostly when I suspect wire harness and connector issues.
love your stuff. Keep it up.
Totally agree with you SD😍😍😍
Thanks for sharing SD👍🏻👍🏻👍🏻
Fantastic tutorial ! You have shown us a golden key 🔑 to fast reliable diagnostic work . Additionally (as any great teacher) you bring us along the journey by challenging us to lay hold of that DISTINCTION in data gathering phase . The final analysis/answer about the load circuitry being open can be done with absolute proof by your method. I’m very appreciative of how dedicated you are to give us the straight talk about the process / industry.
👊🏼 🔥 🔑 💡
Two or more problems on same circuit can happen. Because someone try to repair before you. It is my experience with maintenance in industry.. But it is easy fix when i use metode like yours, test light..
The main point was in making the call on the load itself. The additional wiring tests aren't needed to make that call. But I agree, there are circumstance where you can have multiple issues
@ScannerDanner glad to see a follow up from what I mentioned in the past, just in the beginning so I'm listening! Have a great day friend!
Agree 💯 with the video! About the title, I would argue that the test lights help with speed, if I put a test light in place of the load Then in one shot I tested the power and ground. Not that you can't test it accurately with a meter, just helps with speed. As with most things, there is more than one way to do so correctly.
I have seen a case where the horn pad wire shorted to ground, ran the horn until it died which blew the fuse. So 3 problems on 1 circuit but that’s a different scenario to your 2 problem fuel pump hypothetical situation
I dont have quick access to an amp clamp, so I use a bulb for additional load on circuits and run voltage drop on everything. This was a cool explanation of another way to get enough information to see the state of the whole circuit with different tools.
Edit: just saw two more videos from you on voltage drop with test light LOL gonna check em out
very good. I'm going to have to watch this a few times to make sure the concept is ingrained in my pea brain. thanks for sharing -
Checking the ground side only takes a minute or two. I would just do it. And/Or provide a substitute known good ground. God bless, SD!!!
I wouldn't argue that. You'd also want to load the power side too. But a 200 ma test light is enough in most circumstances. The main point was in making the call on the load itself. The additional wiring tests aren't needed to make that call
Yes! And... a video in real time on a difficult to access ECU ( e.g.Dodge Promaster/ Ford Transit 350)...for a problem under the intake...(cams, coils)
Thank you for such great info Danner 👍🏼
Great Video n Content !! Always Learning, Always Mastering Diagnostics 😁
Definitely agree. But i add one last check to make sure the connctor has no fault
I would really like to see some demos and explanations on using your TopDon scan tools. I have one and would like to learn more on its use.
I have the ArtiDiag600S and love it!
Awesome Outstanding job thanks
you've been following me for a long time my friend. Thank you!
Is it possible for bad ground to cause a fuel pump to overheat and eventually fail? Kind of like a cause and effect type of thing. If yes, then in that scenario, I can imagine an open in a fuel pump and bad ground (but not bad enough to prevent the pump from running) present at the same time. Somebody on the internet was saying that if you lower the voltage going across an electric motor without lowering the load on the motor at the same time, then the motor will overheat and eventually fail. I don't know if any of that is true, but it sounds reasonable. Oh well, none of that matters as long as you have all the materials you need to repair a bad ground stored in your toolbox (That's assuming the technician is conscientious enough to do a voltage drop test on the fuel pump ground after the new fuel pump is installed. If not, then the vehicle gets delivered to the customer with high resistance in the fuel pump ground.)
Yes, in theory, low voltage = slower speed = less counter EMF = higher amperage. But you won't see that on brush type DC electric motors.
@@ScannerDanner That's what I was thinking too
thank you so much Paul
Please correct me if I’m wrong , you have learnt us that positive control outputs (coil integrity) can be tested while the circuit is unloaded by checking voltage before and after , in your example if we found ground before and after it means the coil is not open , but if we found a ground in the ground wire side and “ goust voltage” in the positive side wire it means open coil circuit “also we can use a test light instead of voltmeter”
I know that you are trying to explain more ideas and thought processes to open your students minds
But I don’t think it is nesseccary to hook up scope and amp clamp
Again correct me if I am wrong 😊
"Ghost voltage" is a separate topic and does help ID opens in a circuit
@@ScannerDanner
Forget goust voltage , but can we check the ground existence using voltmeter buzzer test or using test light on both coil ends “unloaded” , to confirm coil integrity?
Oppositely if it is ground control we can check the 12V on both pins “unloaded” to confirm coil integrity
I remember this was one of your diagnostic tracing method 🥹
Chapter 3 material in my book and classes my friend. Ground side switched and power side switched circuits will each have their own unique variables. When at all possible you want to "load the circuit" (current flow). But since we are talking about an open in the load (solenoid winding in this case) a reading of 12v and 0v on the solenoid connector and the solenoid doesn't function, your done. The solenoid is open. You can certainly perform other tests to confirm. Resistance of the coil itself. A test light to substitute the load etc etc.
@@ScannerDanner I’m really sorry , I’m 100% agree with you but I’m saying that for the solenoids we can test it’s integrity without loading the circuit
Negative control output - well known - unloaded : both pins (12 & 12)
Post. cont output - well known - unloaded : both pins (GRD & GRD)
This test for checking coil integrity ☑️
and for checking voltage health and extra resistance existence in the wires , for sure we need to load the circuit to check for any voltage drop on the positive side or voltage raise at the negative side due to undesired resistance
I think there is no conflict between us , and surely your test is gonna test both (coil and wiring) at the same time ☑️
I was revising my infos
Love you and your family 🫡🤍
@mahdiscope2545 we are good my friend! I just didn't understand your questions. Or if you were talking about another method? There are certainly many methods that can be used to come up with the same conclusion. My methods are not the be all, end all. They're just what I use and what I teach. Thank you my friend
👍
Awesome video. Thank you.
This was great!
Good stuff
I think te title of the video might be wrong.
😂
I waited and waited to hear about test lights lol
The description is important here 😅
The facts speake
@johnreid859 I've seen it on Pine Hollow Auto Diagnostics, he uses different amp bulbs to load circuits to verify they can carry the intended load. A test light might light but the circuit might not be able to carry the intended load due to unwanted resistance in the circuit e.g. faulty wire, faulty gnd, relay, etc. Im guessing with an accurate amp meter you could do w/o the bulbs e.g. too high amps/too low amps would indicate something is not correct.
Do you beginner videos like how to use a test light, multimeter, power probe and stuff like that
I'm sorry, is there a question here?
So how do you get around not stressing a high amp coil/motor enough with 200ma to see the problem? Do you eliminate all other possibilities?
I watched the 2 part video on the paid channel and didn't really get the answer
This is an open output solenoid, electric motor, light bulb, or even an input sensor circuit conversation. Your question is what again? Can you rephrase it?
@jeremycameron6594 This video is about finding an open on an electrical component. Why would you, and more importantly, how could you stress a "high amp coil/motor" that is open?
If your "high amp coil/motor" is not working, you don't want to stress the coi/motor. You want to stress the circuit providing power and ground to the coil/motor by removing the coil/motor and replacing it with a test light that draws about the same Amps to see if the circuit is good. If it lights brightly, then the circuit is good. The problem has to be the coil/motor.
If you do the test in the video and find the coil/motor is open and replace it without stressing the circuit with a test light of similar current draw, then it's possible you could also have a problem with the integrity of the circuit but not very probable.
If the coi/motor is easy to access and remove, I prefer replacing it with a test light of similar current draw to troubleshoot. If the coil/motor is difficult to access or remove, then I'll take my chances and do what he does in the video.
@@ScannerDanner I'm sorry. I didn't phrase that very well. Also I didn't realize that it was just open circuit diagnosis. I was just asking that if you take a high amperage circuit with a resistance in the feed, ground, or load, could the circuit still light a 200ma test light and still that resistance not allow the motor/solenoid to work? In this case, would it require a higher amperage test to stress the circuit in order to see the voltage drop? I'm asking because I'm getting ready to buy a tool that would do just that. If it is not necessary, I wouldn't want to waste the money. Thanks Paul.
@jeremycameron6594 think about this senario carefully. If there is a high resistance power feed or ground, I'm 100% going to see it with my voltmeter, because the circuit is energized and my wiring or connector is still plugged in (hugely important). There MUST be current flow to see a voltage drop. The circuit itself is providing the load! If I choose to use a test light in this scenario, I'm doing the same thing! Circuit is plugged in and I'm backprobing and I'm relying on the current flow of the circuit, not my test light, for accuracy of the test. I also would caution you with a test light in this example if the output is still functional because you're relying on the brightness of the bulb for accuracy and depending on how much of a drop is occurring on the feed or ground, you may miss it.
One more piece. You mentioned a high resistance problem in the load itself. That one would be no different than my above example. Voltmeter testing would show normal (12v on the supply and 0v on the ground) or if you were using a test light it would be bright on the feed and not lit on the ground (again circuit plugged in and backprobing with it energized).
This is enough information to make the call on the load itself. BUT, since to load has high resistance and current flow is very low because of it, you're technically not stressing the power and ground circuits like they would normally be with your tests, so now we're back to my love example. I'm saying you're not going to have a wiring problem at the same time you have a faulty load in 99.9% of the times you see this. So if you're concerned that your 200ma incandescent style test light is not enough of a load, then go grap a headlight bulb and make sure it lights on that circuit. I don't ever do this last step. My test light is enough. Why? Because I already know at this point the load is my issue and the final check on the wiring (that I'm not worried about anyway) my test light is good enough
My opinion is that test lights are never my friend. When a bulb is "bright" can you tell the difference between battery voltage and lets say a 1.5 volt drop? If you can good for you. I will stick to voltage testing with some type of meter or scope.
A test light can be your best friend! Here is an example:
A solenoid is melted, you know it's bad, but how is the driver in the module? Substitute the solenoid with a test light and command the driver on! It is the single most accurate test you can do to test circuit integrity and driver control. This is one example of a myriad I can give you where a simple incandescent style test light reigns supreme
@@ScannerDanner don't get me wrong, I will use a test light for certain tests. Sure if I take the melted solenoid out and test signals with a test light to verify the driver's still works. It will not prove out the circuit integrity. Especially a large solenoid such as one on a starter. I've chased my tail a few times trying to use different Amperage bulbs testing circuits. For example, a bad ground wire half corroded at the ground point. Still lights a halogen headlight bulb just fine. Nice and bright to me although there may only be 9.5 volts because of the corroded ground. The computer will report a problem with that same circuit because it sees a problem with the integrity of it. My eyes will only see a massive difference in light, not the subtle difference of a volt or 2. I believe this is why many OE diagnostic plans include ohm measurements of wires from point to point. If service data says this wire should have no more than 5000 ohms resistance from point a to b , then anything above that will trigger a DTC. Circuit could still be intact and support the load of a light bulb but not intact enough to make a computer happy.
The key is to use the existing load in the circuit and perform a voltage drop test. You absolutely will see it! The starter solenoid example you gave. I would never disconnect a solenoid and put a test light on that circuit to say it is okay. ALWAYS leave it plugged in for all of your tests! The ohmmeter is another issue in itself. Service info is wrong on this tool in so many examples! Watch this one and then tell me the ohmmeter was the right tool. Service info called for it here too! th-cam.com/users/shortsyikFzf0c3lQ?si=mVPdILOahmmeTp_p
@@ScannerDanner I will watch it tonight. You and many others are my entertainment/education. I do know about ohm meters and service data being misleading. I absolutely have to pick the right path and tool to figure out a problem, I know this. I once had a front axle actuator in a 2016 ram that was not working. The only tool that found the problem was my power probe. It was showing 2 wires shorted together. It was the harness from the frame rail to the actuator. Trying to show someone with a regular ohm meter showed a perfectly fine harness. The naked eye could not see the short nor could the ohm meter. There was something wrong with the connector and not the wiring but unfortunately no one in the shop had a microscope. All I'm trying to say is a light bulb doesn't tell me the whole truth, kinda like a string of Christmas tree lights when all of them are lit and no one notices a bulb that's a little bit dimmer. Also the voltage drop test is what I was talking about in the original comment. I can see numbers on a meter but not a difference in light intensity unless it is a major drop.
Need help.. 89 e350. 351w no spark.did your test on things. Same volts on both side of coil plug while cranking, test light solid no flicker. 12v test light to pip on module = no coil fire. Hear relay for pump but no spark from coil. Power / grounds seem OK on module wires. Dont know why no spark from coil doing that test. Pick up bad? Coil bad? Module bad? Vanlife.no start, Had to get towed off river bank from Helene. SWVA. Safe now. Just cant move anymore. Thanks.
What is your PIP voltage with KOEO? 0 or 10?
@@ScannerDanner battery volts at 12.2 pip koeo 8.86
@nodotoroam test light to battery ground and touch on and off that PIP wire with KOEO. It should spark each time
@@ScannerDanner thats what I thiught.. watched and watched your videos... NO SPARK. changed coil wire with new, and tried another new plug, no spark at all.
I do hear something when I apply test light to the t-pin stuck in pip. But sounds close to distributor not like at right fender mounted relays for fuel pump.
You are the best!
Not on a coil but let's say we have a electric motor technically you could have a badly designed circuit that was drawing to many amps and melted a lead inside the motor and melted the ground wire at the same time. BUT you would more than likely see the damage.
for sure
More love from Africa🎉❤❤❤
I had my former boss had a chevy van no crank no start he condemned the ground and stated that the ground is good pump must be bad. I put a pump in still same scenario, found the ground was bad 😂 horrible diag skills
You are the best ❤❤
you dont even need a scope for checking current draw
a simple non intrusive amp clamp style meter works..
For sure!
I kinda disagree with this: I would take the old pump and show them that it doesn't work and that it's open... And then I would let them know that there's a SECOND issue with the wire, and charge another fee for that diag.. I might do a little preliminary check or two and see if it's obvious-- but if it wasn't, I'd have to charge for another diag; Especially if it's on a modern car that could have a long trail of connectors and modules just to get to through that pump circuit... (Granted, I very likely would have told them all this up front, before they paid for the pump.. because I'm one of the guys that would have also checked the ground anyway. ;) .. If I'm calling a module or pump, etc.. I like to check EVERYTHING -- twice even. Leave no stone unturned. So I would have found this (fairy tale) 2nd open on the ground and set those expectations early-- that way they could choose to go forward and buy a new pump + more diag -- or just scarp the whole thing, since it's going to take more diag money.
No one will believe you in a shop environment that you now have a wiring problem after changing the pump. That was my point. But I understand your argument too
@@ScannerDanner Right. I understood what you meant-- especially if you had to break the news about the wire issue AFTER the pump was ordered and installed.. That would be a hard sell for sure at that point. :)... But again, just throw 12v onto the old pump and show that it doesn't work ............. - Maybe the bad wire was the initial problem, and then the car sat for 5 years and the bad fuel destroyed the pump: Just saying, it's not impossible...... I wouldn't want to fix the wire for free: that was my point. it could be a rabbit hole that turns into an hour of work. Cheers.
You should....Mr "O" did.
lol you've never worked on the crap i have appearantly lol. i do agree with you it seldom happens on its own. most of the ones i've dealt with with two opens someone else had thier grubby meat hooks on
The main point was in making the call on the load itself. The additional wiring tests aren't needed to make that call :-)
as you suggested, there is always a possibility, for if it can go wrong it will go wrong. but i do not see the neccessity of a high horse rant for checking thew ground side even if there is an open in a coil or whatever. what if the circuit is grounded inside the computer, checking the integrity of the ground side eliminates that from having to diagnose any further. it never hurts to satisfy ones instincts or curiosity when diagnosing, because this is what drives good diagnosticians. even if it appears moot in this situation it is an important step in the algorithm for diagnosing problems. thanks Dan
Too bad you are anti Load Pro. Works
So angry.....
why are you angry?
Danner I have a Problem with my vehicle when I turn the key on to prime my fuel pump nothing happens, later the next day the ignition turn on vehicle starts and then stops about 15 minutes later ,can you help me with some suggestions.
when it is not starting, what are you missing? Spark, fuel pressure, injector pulse? What codes? What year, make and model and engine?
@@ScannerDanner I have fuel pressure at 48 PSI also have spark it runs fine for about 15 minutes and then stops , it’s 2000 dodge Durango 5.9 R/T ,I wish can bring it to.
@@guillerminasoto4690 that wasn't my question. What are you missing when it does NOT start?