Reddit reviews Sperry Instruments STK001 Non-Contact Voltage Tester (VD6504) & GFCI Outlet / Receptacle Tester (GFI6302) Kit, Electrical AC Voltage Detector, Yellow & Black

OP Please do not test this outlet this way. OP stated that the outlet works sometimes and does not other times. Sounds like a short and would not want to risk the short presenting itself at the wrong time and having OP try to work on a live circuit thinking it was off.

https://www.amazon.com/Sperry-Instruments-STK001-Non-Contact-Receptacle/dp/B002JGQAQ6/ref=sr_1_4?ie=UTF8&qid=1541862977&sr=8-4&keywords=line+voltage+tester

I would recommend using this combanation of tools to be safe when working on electrical devices. The one that is not a wall plug can be used to quickly tell if a wire is hot. Hold the button down, touch it to the wire and it will beep if its hot.

In this particular case DO NOT rely soley on if power is coming through items plugged into the switch, as this appears to be a problem.

the buy it for life crowd will always argue for superior quality and buying a good tool. However another random redditor once summarized a different pragmatic:
"Buy a cheap tool, if it does the job you win. If you use it enough to break it you now are justified on buying the good version that might last you a lifetime."
I love harbor freight for economy cheap hand tools.

My exception is buy a good drill/driver. My current house might be close to 50% held together by work from my Milwaukee at this point.

Other tools no one mentioned that will come in handy: Outlet tester/live circuit detector, A stud finder, a set of allen wrenches.

One tool you may not have that will make it a lot safer is a Non contact voltage meter basically you touch the outlet and it will beep if it detects a current. Just incase your breakers aren’t labeled correctly, etc, it’s cheap peace of mind.

Then it’s basically a Phillips head and flat head screw driver. The screws on the sides of the outlets are different colors, make sure they are connected to the correct wire, take pictures of the outlets before you unhook any wires so you’ll know how it goes.

Nope: https://www.amazon.com/Sperry-Instruments-STK001-Non-Contact-Receptacle/dp/B002JGQAQ6/ref=sr_1_6?keywords=live+wire+tester&qid=1563822601&s=gateway&sr=8-6

Hold it up to the wire, if it beeps it's live.

There's a couple handy tools you'll want.

A receptacle tester: https://www.amazon.com/Sperry-Instruments-GFI6302-Receptacle-Professional/dp/B000RUL2UU makes it easy to see if your GFCI outlet is A. wired correctly and B. trips properly. A perk here, is you can also use this tester to see if your normal outlet is chained to a GFCI outlet or on a GFCI breaker, as they'll trip just as well if you use the test button on this tool.

Actually, you can get both in one: https://www.amazon.com/Sperry-Instruments-STK001-Non-Contact-Receptacle/dp/B002JGQAQ6 but you want something handy to check if a wire is live. After I believe I've turned off a circuit, I test it a couple times, usually going to a live circuit too to make sure the tester is also working. I want to be super confident before I touch it.

And yeah, I usually never do electrical work without a friend present, just in case I do something dumb. Never work with electrical alone if you can avoid it.

The box you're looking at is called 2-gang, which is twice as wide as a single gang standard outlet box you're seeing everywhere else. Pull the plate off (looks like just one screw in there) and you'll see two different outlets. You can replace them both, but it's a good idea to figure out why the right one is different. Does the plug type look different? Are they on different breakers? Is the right one upside down (standard convention for an outlet connected to a light switch)?

If there's no difference you can replace both with the same two plug outlets. Having two plugs doesn't require different wiring, they're already tied together (though you can break the connection if one needs to be connected to a switch).

Before you touch anything make sure to flip all breakers that bring power to the box. Typically there's only one but there could be more than one. For example, there could be a a connection between two wires on a different circuit in the same box, unrelated to your plugs. I'd recommend a set of voltages testers like this: Sperry Instruments STK001 Non-Contact Voltage Tester (VD6504) & GFCI Outlet / Receptacle Tester (GFI6302) Kit, Electrical AC Voltage Detector, Yellow & Black https://www.amazon.com/dp/B002JGQAQ6/ref=cm_sw_r_cp_apa_i_Zi9wDbA8G76M5

Test the outlets with the plug tester to ensure they're off. Use the non-contact tester for any other wires you see in the box.

I have this set: Sperry Instruments STK001 Non-Contact Voltage Tester (VD6504) & GFCI Outlet / Receptacle Tester (GFI6302) Kit, Electrical AC Voltage Detector, 2 Pc. Pk., Yellow & Black https://www.amazon.com/dp/B002JGQAQ6/ref=cm_sw_r_cp_api_PR6GAb5KTG4Y6

Basically the plug tests to make sure the outlet is wired properly. You can also use it in a short GFCI run and it will ensure it's wired properly and let you trip the GFCI outlet for testing sake.

Or if you pull the outlet out of the wall you can check to see if it is truly wired properly.

Edit: just remember too, just because that outlet is wired properly doesn't mean the whole run is. This is in regard to physical inspection.