How 3-Light Outlet Testers Work (Future Shock)

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Everyone,

I’ve just finished teaching an RV technician training class on advanced troubleshooting techniques using 3-light testers. Yes, these humble testers can tell you a lot about 120-volt circuit wiring as long as understand their capabilities and shortfalls.

So, I’ll soon be shooting a 10-minute video on 3-light outlet testers for RV owners which I’ll post here in late January. It will demonstrate four different outlet testers, each with their own features and capabilities.

What I’ll be evaluating…

The Klein RT250 has a sample-and-hold circuit that keeps the voltage measurement on screen even after you pull the tester out of the receptacle. Plus it incudes green and red lights that indic ate Correct or Fault wiring conditions along with a detailed display showing more information. It’s available on Amazon HERE.

The Fluke ST120+ is a basic 3-light tester that includes a beeper function, so it’s easy to hear when you flip the right breaker that turns off the power to that branch circuit. It’s available on Amazon HERE.

The Kobalt Digital Display Receptacle Tester combines the functions of a basic 3-light outlet with a digital voltmeter. It’s my go-to quick test for checking line voltage in a branch circuit. It’s only available in Lowe’s stores.

The Southwire 40022S is a basic 3-light outlet tester that includes a GFCI test button. While it doesn’t have any of the extra functions of the Klein, Fluke or Kobalt testers, it does a quick test of basic outlet wiring, as long as you understand its limitations. You can find one on Amazon HERE.

Which one is best?

Which tester is best for you? It depends on your knowledge level and usage. For example, an RV technician may need to test outlets in an RV every day, but an RV owner may only use it several times a season when they plug into a new pedestal.

Which ones do I use?

I already use three of these testers in my seminars and field troubleshooting, so I just need to order the Fluke with the built-in beeper. I can then evaluate all four of them for general testing and troubleshooting. Note that there seems to be hundreds of brands available online and at big box stores, so this is not an exhaustive study. I’m really evaluating features, and this review seems like a good cross section of products. Plus the important thing to know is how to use them to troubleshoot electrical problems. Don’t worry, learning should be fun and (mostly) painless.

Some of the products above have affiliate links. This means that, at zero cost to you, I will earn a commission if you click through the link and finalize a purchase. But feel free to find your best deal anywhere you like.

Let’s play (and test) safely out there… Mike