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Old 05-14-2020, 03:57 PM   #43
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Originally Posted by YC1 View Post
If you are talking about a probe with a light bulb in the handle you do NOT need to connect to a battery. You normally ground the wire via the alligator clip on one end and use the pointy end to probe things. If it lights up, you have power there.
The first issue is finding a "good ground" ! Some people give up and just run a ground wire back to the battery negative terminal. You need a large alligator to clamp on to that ! Others actually take a pair of small locking pliers (Vice Grips), clamp securely on to something close to your test point, and then clip the test lamp clip on to that.
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Old 05-14-2020, 03:59 PM   #44
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Originally Posted by Mudfrog View Post
I have a non contact AC test pen that works similarly.
Great for AC circuits (which every RV has). Not useful for 12VDC which pretty much every RV has !
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Old 05-14-2020, 04:04 PM   #45
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I may have missed this in the previous 44 replies but be careful on your purchase. DO NOT GET AN LED TEST LIGHT OR ONE THAT HAS A METER BUILT IN !

You want an "old fashioned" 12VDC incandescent bulb ! This is important because it proves the wire/circuit can "carry" some current (usually about 1/4A). This is why the test light is better than a meter. A meter will only draw a few THOUSANDTHS of an amp, not enough to prove that there is power to run the item you are testing.

Also, the incandescent light will glow dimly if there is low voltage/current another indicator that something is wrong.
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Old 05-14-2020, 04:54 PM   #46
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Originally Posted by theoldwizard View Post
I may have missed this in the previous 44 replies but be careful on your purchase. DO NOT GET AN LED TEST LIGHT OR ONE THAT HAS A METER BUILT IN !

You want an "old fashioned" 12VDC incandescent bulb ! This is important because it proves the wire/circuit can "carry" some current (usually about 1/4A). This is why the test light is better than a meter. A meter will only draw a few THOUSANDTHS of an amp, not enough to prove that there is power to run the item you are testing.

Also, the incandescent light will glow dimly if there is low voltage/current another indicator that something is wrong.
You have to be careful buying a test light these days. They do like to put LED's in them versus a good old fashion bulb.
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Old 05-14-2020, 05:23 PM   #47
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Originally Posted by Concord View Post
If you've ever tried to diagnose a 12 volt problem, you'll find this the handiest thing! The logic probe from harbor freight. (it's only shortcoming is too short of a wire.. I added 20 feet to mine.)
Connect it to the battery... Then anything you touch with the probe lights up a green light if you touch ground, red if you touch hot. Ten bucks.
Let me know if you've got one and if you agree. Attachment 284601
I have Sun and Fluke plus others but this is as handy as it gets for something in the tote bag

Have one of these in the bag that is used for lighting and brakes primarily

Thanks for posting
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Old 05-14-2020, 05:56 PM   #48
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Originally Posted by theoldwizard View Post
The first issue is finding a "good ground" ! Some people give up and just run a ground wire back to the battery negative terminal. You need a large alligator to clamp on to that ! Others actually take a pair of small locking pliers (Vice Grips), clamp securely on to something close to your test point, and then clip the test lamp clip on to that.
I learn something new every day! I will remember to use vice grips to help find a good ground.
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Old 05-14-2020, 06:41 PM   #49
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Most just have a single connector for the Ground then the Probe will see if the Circuit is good.

Baffled by the second connector.

Use mine all the time to just see if I have 12 Volts at the Location.


Without both a positive and negative wire it would not be able to light up when touching ground to ground since it has no internal battery.

I prefer knowing the actual voltage though since for trouble shooting you will too many times get a good indication from a trouble light even when there is a low voltage situation from a bad connection, switch, etc that will only pass enough power to run the tiny LED bulb but not enough to run a fan, control board, etc so a meter is preferable.

I have a number of those lights and they mostly collect dust and end up getting in the way. More often they get used without the wire plugged in as a probe to align screw holes or as a scratch awl.
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Old 05-14-2020, 07:32 PM   #50
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Itís a copy of the power probe that's been out for 20 years. I use one all the time, almost daily. The power probe is better IMO because you can do what this one does (identify either positive or negative) but you can also feed the circuit with power or ground. It also has a built in circuit breaker so if you feed power to a ground it trips the breaker. Iím not putting this down, I really like a lot of harbor freight products and spend lots with them every year!

I would hope it's better at $70 to $150 each, heh.
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Old 05-14-2020, 07:59 PM   #51
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What is the right tool depends on what the task is. A multi meter is the best single starting item. Simple test probes, single or two wire are simple and cheap, but different, a Power Probe IV solves some more difficult problems and can be used for simple stuff as well. The Simpson 260 series meters are great reliable tools, pushing the $300.00 mark.

Here's a link for the Power Probe IV since I get the feeling many folks here have not seen them. About $180.00.

https://www.amazon.com/dp/B00NPY02EW...v_ov_lig_dp_it

Any tool is only a useful as the skill level of the user and their ability to understand when to use it and how to understand the results.
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Old 05-14-2020, 09:11 PM   #52
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[QUOTE=rarebear.nm;

Any tool is only a useful as the skill level of the user and their ability to understand when to use it and how to understand the results.[/QUOTE]

So true!

I made a simple test light out of a 7 watt 1156 bulb and an old clamp.

Used a old socket that I brazed a piece of welding rod to, (ground to a sharp point) to hold the bulb.

That old test light would tell me what the voltage was, how good the ground was, if there was a bad connection down line, or which fuse was blown.

I guess 40+ years doing trouble shooting gives you a little edge.

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Old 05-15-2020, 05:50 AM   #53
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I prefer knowing the actual voltage though since for trouble shooting you will too many times get a good indication from a trouble light even when there is a low voltage situation from a bad connection, switch, etc that will only pass enough power to run the tiny LED bulb but not enough to run a fan, control board, etc so a meter is preferable.
Which is why I said get a 12VDC test light with and incandescent bulb !

After you use it a few times, you will recognize he brightness (or lack there of) to indicate low voltage.
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Old 05-15-2020, 06:00 AM   #54
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.............

....

Any tool is only a useful as the skill level of the user and their ability to understand when to use it and how to understand the results.

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Old 05-15-2020, 06:01 AM   #55
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... a Power Probe IV solves some more difficult problems and can be used for simple stuff as well.
.
.
.
Any tool is only a useful as the skill level of the user and their ability to understand when to use it and how to understand the results.
While a Power Probe, in the proper hands, can help diagnose SOME electric issues, I DO NOT RECOMMEND IT, especially for "rookies" !


There are a couple of YouTube channels that specialize in automotive diagnostics. They use a 12V test light (including a high current, 4A+) a lot. They occasionally use a Power Probe. Less often then than a meter or an oscilloscope. These guys make their living diagnosing 12VDC electrical issues. Their YouTube channels are just "gravy".

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Old 05-15-2020, 06:56 AM   #56
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Great for AC circuits (which every RV has). Not useful for 12VDC which pretty much every RV has !
I assume you are referring to the one at Harbor Freight. Why do you believe it is useless for 12vdc?
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