AC circuit tester result on inverter

Thread Starter


Joined Jul 17, 2009
I'm working on a project vehicle, an RV basically, and I just wired up the interior (AC) and installed an inverter.
Upon completion of the work, I fired up the system, and using a standard Micronta Radio Shack 22-101 tester, I checked the outlets.

Wouldn't you know, the code I got was the only one not shown: all 3 lights (2 green, 1 red) lit up. I did combine the grounds on both inverter circuits in my wiring, but I can't see this having any negative effect.
A house lamp plugged in seemed to work fine. The only additional thing I have not done yet is to check the tester right on the inverter's outlet (bypass all my wiring).
Anybody have any idea what that code could possibly mean?
Thanks in advance,
That's the code for "Get the AC Voltmeter and do some measurements."
Seriously though, a search of the company's web site doesn't bring the product up, though Tripplite makes one just like it:

Sounds to me like you have a defective tester. What's the make and model of the inverter and do they have an online .pdf of the instruction manual?

Do you have an AC Voltmeter or DMM?
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Thread Starter


Joined Jul 17, 2009
I thought it might be defective too, but I tried it on a known-grounded house socket and got the correct readout.


Joined Jul 7, 2009
I'm writing an article on AC safety and I made the attached picture of how these AC outlet testers work. They're basically neon bulbs with current-limiting resistors that are connected as in the attached picture. (Note: if I'm in error, someone please let me know, as I do want to get it right. But this just quickly simulates what you'd normally measure with a voltmeter.)

The only way I can see that you'd get the three lamps lit simultaneously is if there were at least two different voltages available rather than the usual one. Because you state the tester works normally on a regular socket, I'd assume it's working OK. Then you have something significantly wrong with your wiring and you MUST get an AC voltmeter and troubleshoot it. Here's one of many possibilities: the normal 120 VAC is on the hot lead with respect to ground. But the neutral has 60 VAC on it with respect to ground and in-phase with the hot voltage. Then, assuming the neon bulbs will light with 60 VAC, you'd see the three lights on.

I almost never remember where my outlet tester is, but I always know where my Fluke DMM is 24 hours per day. :p