Test light with positive and negative clamps

[Greg85mcss]

I got a “you ****” deal a few years back and threw some of the stuff I didn’t need in a drawer without really looking at it. Well, I grabbed that test light to check a fuse panel and it has 2 clamps on it. My other one only has a ground clamp. What is the other clamp for?


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[crf450x]

I'd imagine the positive clamp would be so you can use the probe to test for ground.

 

[CoogarXR]

Is this an inline test lamp? Like it has a clamp on both ends? Or does it still have a probe?

An inline lamp with two clamps would be nice for testing something without having to touch it. For instance, you clamp it across a test point under the hood, then go inside the car and crank the ignition and watch for the light, etc.

I use a regular test lamp like this, but I just clip a test lead on the probe end.

 

[Greg85mcss]

That sounds pretty cool, but it’s got both clamps on one end and a probe on the other. I actually found a YouTube video that seems like what it is. You can hook up both and it lights up red for power green for ground. If so I wish I had known cause it would have come in handy for a job I did a few months ago.


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[CoogarXR]

That does sound pretty neat!

 

[bert1913]

https://www.harborfreight.com/computer-safe-automotive-logic-probe-63597.html

 

[Bretny]

I'd imagine the positive clamp would be so you can use the probe to test for ground.

Lol thats funny....all you need to do to test for ground is to put the single clamp on positive.

 

[bob15]

Mac/OTC also makes/sells one:

 

[crf450x]

Lol thats funny....all you need to do to test for ground is to put the single clamp on positive.

Then you can't test for power.

....I see what I did there. Whoops

 

[GTA Matt]

An led test light is better suited for the trash can. If it can't load a circuit, it's worthless and will mislead you.

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[Diesel Mercedes]

An led test light is better suited for the trash can. If it can't load a circuit, it's worthless and will mislead you.

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Yup.

 

[rustyzman]

Sounds like a 12v logic probe. Used to use one for power window diagnosis. I liked it. It does not load the circuit, which can be beneficial with computer circuits as well.

For loading a circuit, a headlight with a couple leads soldered on is about the best. It will pull about 5amps and will identify poor connections. Of course only use it on circuits that will normally run at that current level or higher. Regular test lights are only 30-100mA and usually won't identify marginal circuits in my experience. Just my way, your mileage may vary...

 

[jl4c]

That sounds pretty cool, but it’s got both clamps on one end and a probe on the other. I actually found a YouTube video that seems like what it is. You can hook up both and it lights up red for power green for ground.

Power Probe perhaps? I have the model 3 version. Very handy.

 

[Greg85mcss]

That’s what I’d like eventually but I just started at an independent shop, so there’s a lot of stuff that was provided before I need to get pretty soon. I tried the one I was asking about and it doesn’t work anyways but this has been a good discussion.


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[ImportTuner]

An led test light is better suited for the trash can. If it can't load a circuit, it's worthless and will mislead you.

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Not really .. working on a 2014 Mustang, would not start. Used test light to determine fuel pump was not getting any voltage.

 

[6PTsocket]

An led test light is better suited for the trash can. If it can't load a circuit, it's worthless and will mislead you.

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In many cases, with modern cars, that is exactly what you do not want to do. For high power circuits, what you say may be true but put a load on some sensor circuit and you could be pricing a new computer. Multimeters (DMMs) have an impedence of 10 megohms so they pull microamps and do not affect the circuit they are trying to read.

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[383 240z]

It is a logic probe. It is NOT a test light. It's a very useful tool for diag work. I love mine.
I did, however, extend the leads so I can hook to the battery and reach the other end of the car.

 

[GTA Matt]

Not really .. working on a 2014 Mustang, would not start. Used test light to determine fuel pump was not getting any voltage.

You missed the point. Sure it (led) can tell you there is no power, but wait until it tells you there IS power, when you have a fuzzy connector or a green wire. It will burn your ***.

In many cases, with modern cars, that is exactly what you do not want to do. For high power circuits, what you say may be true but put a load on some sensor circuit and you could be pricing a new computer. Multimeters (DMMs) have an impedence of 10 megohms so they pull microamps and do not affect the circuit they are trying to read.

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Give me an example of a 12v circuit that will be damaged by an incandescent test light. I can't think of one and nobody has ever given a legitimate example.

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[Gmonkee]

A LED logic probe is very useful once you learn how to use one. My boss has basic units and can resolve most any problem.

Mine is 6-12-24vdc and gives the volt range as well as the polarity.
For heavy truck work that is quite handy. It cost all of a dollar.

 

[WittHay]

Isn't the 2 wire LED test light a limited use tool for checking pulse on things like fuel injectors and crank sensors. You have to have both leads hooked up for the LED's to work

For working on old ****, I have always used the incandescent test lights. The digital read out type is handy when working with multiple batteries and checking alternator output voltage on equipment.

 

[6PTsocket]

You missed the point. Sure it (led) can tell you there is no power, but wait until it tells you there IS power, when you have a fuzzy connector or a green wire. It will burn your ***.Give me an example of a 12v circuit that will be damaged by an incandescent test light. I can't think of one and nobody has ever given a legitimate example.

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I was referring to the headlight that was suggested as a test light with the intent of drawing a lot of current.

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[Gmonkee]

As my use of test equiptment is sporadic I prefer stuff without a battery. Analog meters and logic probes for both home and auto work.

I finished wiring my home using only a phase detector thing Harry Potter would have loved. It told me which was hot or common and if it carried voltage. From there the rest was a logic exersize.

Going from there to dc wiring was automatic really. Just a different device equally simple. Your brain is the power behind the magic. The device just tells you what the wire carries.