Klein Tools Basic Electrical Test Kit Review 

I have one of these, and it seems to work like this: for AC, both LEDs for each step of the ladder light up. For DC, one side or the other will light up depending on polarity. In your example, when you have it hooked up to the power supply with red-to-red and black-to-black, the left LED lights up. When you swap it, the right LED lights up. I just tested mine and it works the same way. Klein also makes another tester (the ET40) that works similarly with two LEDs lighting up for AC and only one or the other lighting for DC to indicate polarity.

The lights changed side when you reversed the test leads because on DC the side that lights up indicates the DC polarity, which you reversed when you swapped the leads. Both sides light up on AC because AC current flows in both directions.

I agree that the tool is confusing... Its confusing because it isn't a multimeter! I'm not sure if you're aware of this but electrical engineers and physicists often look at both the AC and DC voltages of the same signals. That is because DC and AC are always a component of one another! You could create a power supply that outputs a 40V AC signal with a 20V DC offset. I have the same tool and I think what you're missing is that when one led in the row is on that means it is DC, if two LEDs are on in the row then it is AC.

My wife had a good giggle with you tonight. 👍🤣🐈

The leds are so bright they light up the whole vicinity.

You can't go wrong with Klein tools. I've used them for almost 40 years. You get quality. Btw it's just reverse polarity making the tester act up.

Cool review..

I came in here to see about the klien v tester and mine lights all of them up when i put it in an outlet.

Good informative video interesting defenitly looks defective

Does it indicate at all on 12 vdc, or is the minimum 30 vdc ?

I'm shocked that klien wired it wrong wow

return it and see if they put it back on the shelf

The tester never works