Loading circuits

Michael Owner/Technician Quakertown, Pennsylvania Posted   Latest  

What is your preferred method to load test a circuit before condemning a part? Headlight? "load pro"? etc.. Is there a time where you don't feel it's necessary to do this? What if you can disconnect that o2 sensor connector to load it but you can't disconnect the other end (at the PCM) that's buried 300 feet behind the dash? I always want to be as thorough as possible especially when i'm spending the customers money. If you do your loaded circuit testing with a head lamp what do you use and what is a good baseline to go by on choosing the right bulb.

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Victor Owner/Technician
Doral, Florida
Victor Default
 

Any headlamp bulb with at least a 100 watt rating is good enough for me(100/12= 8.3amps)

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Marlin Technician
Estacada, Oregon
Marlin Default
 

That will let the smoke out on some circuits. This isn't a one-size-fits-all scenario.

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David Instructor
Kokomo, Indiana
David Default
 

Hi Michael, A load pro is a great tool but not an actual full blown substitute load. A headlight on most automotive circuits utilizing 18 gauge (or larger) wiring will not damage that wiring if applied for a short period. Regarding more customizable substitute loads, most decade boxes do NOT have a high enough wattage rating to allow you to use them as a substitute load in a series circuit. I…

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Sam Mobile Technician
Flint, Michigan
Sam Default
 

Michael, Why do you want to disconnect the other end? I always load similar to what the circuit is designed. I have all of my test lights marked with amperage draw. I use a homemade 3157 dual filament test light for most circuits. About a 3 amp load. I have put banana jacks and place it in my meter so I can load and check for voltage drop at same time. I rarely use a regular test light anymore.

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Michael Owner/Technician
Annapolis, Maryland
Michael Default
 

Hey Sam can you post some pictures of it?

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Sam Mobile Technician
Flint, Michigan
Sam Default
 

I will get a picture of the contraption today

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Michael Owner/Technician
Quakertown, Pennsylvania
Michael Default
 

Sam, i'm sorry what I meant in disconnecting the other end I was referring to doing an open circuit test. My post had a few questions on testing circuits in general.

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Stuart Mobile Technician
Blue Island, Illinois
Stuart Default
 

I still use the resistance substitution box that I built years ago when I was a bench technician​.​It's a little bulky but does the job whenever I need to use it​.​They sell those type devices at Fry Electronics​.​You can vary the resistance and wattage with it.

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

Yours sounds just like mine. 3.6 A and stackable banana jacks off of broken OTC test leads (like the GM ones),

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Sam Mobile Technician
Flint, Michigan
Sam Default
 

Exactly

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Robert Engineer
Durham, North Carolina
Robert Default
 

Hello Michael, We developed this years ago after getting peppered with ECU purchases which turned out to be a voltage drop problem on the primary ignition circuit. Look at the video. It is a recreation, the issues was mostly on Mercedes ML models in the late 90s. They had a problem in the fuse boxes with corrosion. But the behavior was exactly as we show in the video. There are some in stock…

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Michael Owner/Technician
Quakertown, Pennsylvania
Michael Default
 

Robert, can you let me know how to get a hold of one?

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Robert Engineer
Durham, North Carolina
Robert Default
 

Sure, Droplink probe. Call main BlueLink number: …

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Michael Owner/Technician
Quakertown, Pennsylvania
Michael Default
 

Bob, how exactly is it able to see how much current the circuit can carry?

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Robert Engineer
Durham, North Carolina
Robert Default
 

It makes an assumption. If you load a circuit, below 8 Volts there is not enough energy to run things. Many things in a vehicle like the PCM, solenoids, small motors, generally will operate down to 8 Volts. The probe applies a load pulse. Very rapid rise and fall in the current. When the voltage between the leads hits 8 Volts it stops but takes a snapshot of the actual current which is flowing.

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Dmitriy Analyst
Toronto, Ontario
Dmitriy Default
   

Bob, is it possible for the probe to be reviewed by someone like TrainedByTechs? Does Drew Tech have any plans for the device (if that info can be shared)? It just looks like a unique product that few people are aware of...

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Robert Engineer
Durham, North Carolina
Robert Default
 

Hello Dmitriy, I don't see why not. We are working through some things which will be announced soon. I have introduced the product to quite a few people. I can have a room full of students. Half have no idea what I am talking about when I bring up voltage drops. Only a handful of the rest can afford, or choose to afford buying the tool. Those that did love it! We still have some left and plan…

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Randy Diagnostician
Glendora, California
Randy Default
 

HI bob this looks like a realy cool tool were can i get one ????

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Robert Engineer
Durham, North Carolina
Robert Default
 

Hello Randy, Thanks for the interest. We are in the process of moving our website so the ordering feature is temporarily turned off. Right now you can get one but you need to contact the office directly. Sorry for the inconvenience. Should not be long and everything will be sorted out. …

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Victor Owner/Technician
Doral, Florida
Victor Default
 

I do hope that your website is back up and running soon because my only option is via online purchase.

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Tony Inspector
Santa Barbara, California
Tony Default
 

I've use this cheap, homemade load box a few times. Pulls about 3 - 18 amps depending on how many bulbs are in their sockets. 1157 bulbs.

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Pedro Mechanic
Tacoma, Washington
Pedro Default
 

I learn in a carquest class recently you can use the power probe hook it has a hot shot feature and also voltage drop pro I would like to get one it seem like a good tool for load testing also a pwm power pro for pulse width or duty cycle loads any one that has use them can we get some feed back please

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Joel Diagnostician
Soquel, California
Joel Default
 

I have that unit on the rh, the signal sent out is dc variable , the unit is not sending out pulse width signal , I have activacted throttle body and when you get to above 75% duty cycle start opening hard to keep it in one position or open it little by little as it goes fully open .

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Gary Owner/Technician
Peck, Michigan
Gary Default
 

I just usually use a 4652 headlamp. I draws about a 5 amps. My test lights run about 50-200 miliamps. The 5 amps usually offers enough load to test the integrity of the circuit without getting me into too much trouble.

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Michael Owner/Technician
Quakertown, Pennsylvania
Michael Default
 

Are there any precautions when loading computer driver circuits?

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Robert Engineer
Durham, North Carolina
Robert Default
 

No, The probe will not load anything below 8 Volts. But even if it did the pulse is so short that there is very little total energy transferred. It would not damage a reference voltage if it were to apply the pulse. Bob …

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David Instructor
Kokomo, Indiana
David Default
 

I disconnect any related circuits connected to solid state devices such as modules and computers prior to probing with grounds, power sources or connecting substitute loads. When you do this first step, you then are simply working with copper wiring in a harness instead of expensive modules. There is too great of a chance of making a mistake whenever you connect something like a Power Probe or…

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Robert Engineer
Durham, North Carolina
Robert Default
 

You are exactly right David. We have all let the smoke out of something at one point or another, learned the hard way. It is almost a right of passage! If you apply hard ground or power to something you really need to be sure exactly where and if it is appropriate. We can only do our best to teach the next generation by sharing our stories.

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Robert Engineer
Durham, North Carolina
Robert Default
 

David, I remembered this story. You may find it amusing: As the inventor of the DropLink probe one would suspect that I consider myself open to new diagnostic concepts but this brief story highlights how we can easily get stuck in approaching problems the same way. I am nearly 50 years old and have done electrical trouble shooting nearly all my life. My son, 11 at the time had discussed with…

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Victor Owner/Technician
Doral, Florida
Victor Default
 

It however appears to be no longer available.

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Mike Technician
St. Louis, Missouri
Mike Default
 

8h Robert Beckmann Engineer BlueLink Diagnostic Solutions, Inc. in Durham, North Carolina Droplink probe. Call main BlueLink number: … Victor, from above post. I own one and it works great...Mike.

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Victor Owner/Technician
Doral, Florida
Victor Default
 

My buying choice is online.

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