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05-14-2020, 03:57 PM
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#43
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Senior Member
Join Date: May 2017
Posts: 1,299
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Quote:
Originally Posted by YC1
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.
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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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Retired. 31 year of automotive engineering for one of the Detroit 3, specializing in Powertrain Control Systems.
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05-14-2020, 03:59 PM
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#44
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Senior Member
Join Date: May 2017
Posts: 1,299
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Quote:
Originally Posted by Mudfrog
I have a non contact AC test pen that works similarly.
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Great for AC circuits (which every RV has). Not useful for 12VDC which pretty much every RV has !
__________________
Retired. 31 year of automotive engineering for one of the Detroit 3, specializing in Powertrain Control Systems.
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05-14-2020, 04:04 PM
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#45
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Senior Member
Join Date: May 2017
Posts: 1,299
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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.
__________________
Retired. 31 year of automotive engineering for one of the Detroit 3, specializing in Powertrain Control Systems.
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05-14-2020, 04:54 PM
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#46
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Senior Member
Join Date: Jun 2011
Location: FL
Posts: 11,441
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Quote:
Originally Posted by theoldwizard
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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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.
__________________
Certified Senior Electronic Technician, Telecommunications Engineer, Telecommunications repair Service Center Owner, Original owner HR 2008
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05-14-2020, 05:23 PM
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#47
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Registered User
Join Date: Mar 2019
Posts: 1,336
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Quote:
Originally Posted by Concord
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
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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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05-14-2020, 05:56 PM
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#48
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Senior Member
Join Date: Sep 2019
Location: Minne-so-cold
Posts: 708
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Quote:
Originally Posted by theoldwizard
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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I learn something new every day! I will remember to use vice grips to help find a good ground.
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05-14-2020, 06:41 PM
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#49
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Senior Member
Join Date: Nov 2005
Posts: 4,063
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Quote:
Originally Posted by Busskipper
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.
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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.
__________________
Neil V
2001 Winnebago Adventurer WFG35U
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05-14-2020, 07:32 PM
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#50
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Registered User
Join Date: Aug 2019
Posts: 674
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Quote:
Originally Posted by InfinityJim
It’s 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. I’m not putting this down, I really like a lot of harbor freight products and spend lots with them every year!
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I would hope it's better at $70 to $150 each, heh.
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05-14-2020, 07:59 PM
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#51
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Senior Member
Excel Owners Club Winnebago Owners Club Ford Super Duty Owner
Join Date: Aug 2014
Location: Santa Fe, NM
Posts: 6,808
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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.
__________________
Fred & Denise (RVM157) New Mexico
2007 Excel Classic 30RSO & Coach House 272XL E450
2007 RAM 3500, Diesel, 6Spd Auto, SWD, 4x4, CC & LB
[SIGPIC][/SIGPIC]
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05-14-2020, 09:11 PM
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#52
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Senior Member
Winnebago Owners Club Workhorse Chassis Owner
Join Date: May 2016
Location: Kamloops, BC, 60 miles from the Center of the Universe according to the Rinpoche, of the SF monks.
Posts: 7,387
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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.
Happy Glamping.
__________________
Happy Glamping, Norman & Elna. 2008 Winnebago Adventurer 38J, W24, dozens of small thirsty ponies. Retired after 40 years wrenching on trucks! 2010 Ford Ranger toad with bicycles or KLR 650 in the back. Easy to spot an RVer, they always walk around with a screwdriver or wrench in one hand!
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05-15-2020, 05:50 AM
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#53
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Senior Member
Join Date: May 2017
Posts: 1,299
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Quote:
Originally Posted by NeilV
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.
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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.
__________________
Retired. 31 year of automotive engineering for one of the Detroit 3, specializing in Powertrain Control Systems.
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05-15-2020, 06:00 AM
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#54
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Senior Member
Join Date: Sep 2007
Location: Grasonville, MD -- Golden, CO
Posts: 6,222
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Quote:
Originally Posted by 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.
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__________________
Busskipper
Location - Grasonville, Maryland - and/or - Superior, Colorado
2005 Travel Supreme 42DS04 - GX470 Toad
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05-15-2020, 06:01 AM
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#55
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Senior Member
Join Date: May 2017
Posts: 1,299
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Quote:
Originally Posted by rarebear.nm
... a Power Probe IV solves some more difficult problems and can be used for simple stuff as well.
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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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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".
South Main Auto
Pine Hollow Auto Diagnostics
__________________
Retired. 31 year of automotive engineering for one of the Detroit 3, specializing in Powertrain Control Systems.
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05-15-2020, 06:56 AM
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#56
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Registered User
Join Date: Oct 2018
Posts: 412
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Quote:
Originally Posted by theoldwizard
Great for AC circuits (which every RV has). Not useful for 12VDC which pretty much every RV has !
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I assume you are referring to the one at Harbor Freight. Why do you believe it is useless for 12vdc?
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