How to Diagnose and Check a 120 Volt AC Wall Outlet

Fred's Appliance Academy
January 28, 2020

Hey everyone. Tim with Fred’s Appliance Academy here with another great video for you today. In today’s video, we’re going to show you how to diagnose and check a 120 volt AC wall outlet in a customer’s home. Now, whether we’re checking the 120-volt outlets or we’re checking the 240-volt outlets, outlets and customer’s home electrical is the most overlooked, misdiagnosed issue in a home when it comes to repairing an appliance.

It could just be that and that’s what’s causing their brand new unit not to work properly. And once as a technician, you start ordering parts because you second guess yourself where you don’t know how to correctly check an outlet. What you look like is that you’re, what we consider married to the unit. It’s very hard for us to prove to the customer that this is absolutely what it needs and what is wrong with the unit.

So we’re going to show you the ways that we do it here with the students and what we suggest even in the field with your veteran technicians. There are a lot of helpful tools out there that can help you check outlets and voltage. For instance, we have what’s called a foreign voltage detector. What this does is this is a stick that we should be able to stick right into the outlet here and wherever we don’t have voltage, we should not hear that beep.

I just went into the ground and it gave me a beep and I know that there’s no voltage on the ground. I know that this outlet is correct and we’ll be able to show you that. So this is very inaccurate and it shows not only the inaccuracy, but it doesn’t show you the voltage reading there. I can rub it up against my sleep and generate voltage that’s just from static electricity.

Technicians will also use this voltage detector here as well where it’ll just tell you if it’s DC or AC voltage, whether it’s 120 or 240 volts. And again, it’s just sticking it right into the outlets here, just like you would a meter. But instead it has a little lever that will beep and let you know where your voltage is at, whether it’s 120, 240.

The last one that we have is the outlet plug tester with what they have out there. It gives every scenario out there. And when a customer would plug this into their outlet, they’d be able to tell that if they had an open ground or a hot neutral reversed, hot ground reversed, open neutral. It’ll tell them all the different scenarios and it’s just very easy to plug this guy in right there to see that you have a correct outlet. But again, it doesn’t tell you how much voltage is actually at that outlet.

So with that said, what we use in the field is either a digital or analog meter, which are going to be the most accurate things for you to check. These other things here would be great visuals for the customer after you’ve diagnosed the outlet correctly. So what we do is we will use our digital meter. And we set that to AC voltage. And what we have our students do is we have our students draw out the outlet beforehand.

So what we would have is I’d have this outlet here and between my line and my neutral, which are the two top areas there, we should have 120 volts. And even with the digital meter and trying to hook this up, it’s even giving us a hard time to try to figure out what that voltage is. So you have to play with the lines there to make sure that you’re picking it up in there. We finally just got it and we showed that we had a 115 volts.

If I go down to my line and my ground, this is another one where you can see the shortness of these meter leads. You want to make sure you have good meter leads to be able to tell where we’re at when we come to voltage. And there we go, 116 volts, 115 volts. So that’s your digital meter that’ll show you that. Make sure you’re setting it for the proper voltage setting. Again, this would be AC volts. If you set it for DC you would more than likely open a fuse in that and cause a short. And the meter’s no good to you after that unless you replace the fuse.

For our analog meter here, which I prefer the most, analog meters will catch voltage drops. They’re more accurate. They won’t jump around as much as a digital meter will and again just keeping it in good shape. Some of these actually come with little protectors on them so you don’t stab yourself in the hands. You could put those over them. You don’t want to get them tarnished or discolored because what’ll end up happening is you can get false readings as well.

But again, it’s the same principle. And learning how to read an analog meter is a little bit different. And we do that a little bit further in the course to teach the students because an analog meter is just not used much anymore in the field. But that’s saved for another video there.

So what we’ll do again is to just go across our line and our neutral and according to my analog meter, I have a steady 120 volt AC in this outlet here. And then I would just go ahead and check my line to my ground to make sure I have the same thing. Now if I had anything different by writing out and drawing out that outlet and compare it to my different scenarios, showing that I have no voltage between neutral and line, but I have voltage between line and ground where I’m supposed to have, that shows me one reading.

So I know something’s open, something’s missing or not there. And just by checking between neutral and ground showing nothing that shows that I have an open neutral. So customers complaints on different things may be my control board’s not turning on. Or when I go to light my stove it keeps on clicking. And there’s just different things that open neutral is going to cause and just a lot of weird readings that the technician may even get across the outlet.

So again, knowing how to read an outlet properly and using a meter instead of the easy way, use those easy ways to show the customer with the visualization that you can give them. Be the technician and use the tools that are given to you that you actually have to go out and learn how to use. So you know for sure what’s going on with that outlet.

I hope you guys liked the video. The voltage is very just, it’s very important to know in the field. And if you liked it, like, subscribe, keep an eye out for more videos. We’ll do a 240 volt video here shortly and get that out there. Tim with Fred’s Appliance Academy, where we’re training tomorrow’s technicians today.

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