How to Assemble a 120-volt Auxiliary Power Supply for Appliance Repair Diagnostics


Hey everyone, Tim with Fred’s appliance Academy here with another great video for you today. In the last two videos, we showed you how to make a mini fuse breaker and a split phase compressor tester. Two very helpful tools that you’ll use almost every day in the field to make your job a lot easier and to give you a more thorough diagnosis of the unit.

In today’s video, we’re going to show you how to make a 120-volt auxiliary power supply that’s going to be able to power any component that requires 120 volts. The supplies you can get right off of Amazon, they cost less than $20, they’re in the description so feel free to click on the link, it’ll take you right to the page. All we’re going to need are just a couple of hand tools to put this together. The time on this is about 10 minutes and you’ll have a good working tool.

Let’s go over the supplies that we’re going to need here. We’re going to start with our alligator leads here, which we’re going to indicate the colors by using heat shrink. We have our line neutral and we have our ground there. We also need a 120-volt three-wire power supply, a shallow switch box, a single-pole, single-throw light switch, a switch cover, and one wire nut. Tools required for this will be a number one square bit or Phillips screwdriver, flat blade screwdriver, a pair of wire strippers and a heat source; which we’re going to use a butane small torch.

Let’s go ahead and assemble this and we’re going to start by placing the wiring for the alligator leads inside the box. Choose either end, it doesn’t matter and just push those wires right through. If you’re having some trouble with the wires in there, you can bend the tabs down to make it easier. You’re going to also go ahead and push your power supply in the box as well. Once you have those in there, you can start stripping your wires back. You’ll need enough to be able to wrap them around the switch and then enough to combine your grounds together as well. Then also on the power supply cord, make sure when you’re stripping this back, you’re not going too deep and you’re stripping back the actual wires inside the insulator here. You’ll want just about that much of wire there. We’ll go ahead and strip these back as well. Again, just enough to wrap them around the screws so you can have a nice tight connection.

Then you’re going to take your light switch. We have two brass screws there, which is going to be our hot side and we have a ground. So we’re going to find our two hots, the black in the power supply cord and then we’re going to locate the red one here on our alligator clips. We’re going to go ahead and wrap these around clockwise so that way there the wires do not work themselves out as we screw these down. We’re going to take our black one here, wrap that around clockwise as well. Make sure they’re nice and tight. We’re going to take our green off of our cord and then we’re going to find the green from our alligator leads here and we’re going to combine those together. You could just push these up and then down to find which one’s moving and you can twist those together. Make sure that you’re not wrapped around here so you’re not getting a poor connection or you’re trying to stretch wiring. Wrap those two wires together and attach it to the green screw on the switch. Again, clockwise. Nice and tight in there.

Once we have everything connected here, we’re going to want to go ahead and connect our neutrals. What you want to do is you want to grab your neutral wire off your alligator lead and then the white wire off your power supply. Don’t twist these wires together. Just simply place them next to each other using a wire nut. Go ahead and screw that wire nut down and the wires should actually start to twist on their own. That indicates that they’re braiding together. And then to top it off, we’re going to use a piece of electrical tape. Again, we’re going to wrap this around clockwise, the way we spun the wire nut so it does not come loose. Make sure you’re using the electrical tape. You want to make sure these wires don’t come loose and you can cause some arcing inside the box.

Once you have that taped off, go ahead and place your switch. If you have to adjust your wiring, feel free to do so. Go ahead, take your switch, line them up with the holes that are on this switch box there and then make sure the wire nut is off to the side. You don’t want to squeeze that wire nut with the switch itself. Use our number one square bit here and I’m going to start one side here. Carefully watching that I’m not squeezing or pinching any of the other wires. I’m going to go ahead and start the other side here. Again, watching that I don’t squeeze or pinch any of the wires. It’s very important to keep an eye on it. Really no power tools are needed.

Then you just want to give this a little bit of an even install here. Before tightening down all the way, make sure the wires are not touching each other, squeezed, pinched, and then go ahead and tighten the rest of the way down until it’s tight. Okay, we have our switch that’s now tight inside that box there. Go ahead and place that wire nut down. Get your switch cover, use your flat blade screwdriver here. You’re going to screw that right into the switch. There are two holes on the switch for that. Don’t tighten down too tight or you will crack the cover. You just might have to adjust the cover just a hair to get to that last screw hole.

Okay, now that we have this tight, the last thing that we’re going to want to do before testing this is we’re going to want to go ahead and we’re going to want to shrink our heat shrink here. Again, I’m just going to use this small butane torch here. You don’t want to focus the heat directly on the wiring. You want to give it a waving motion and watching that shrink tubing shrink right around the wire there. You don’t want to burn the wire. That one’s done. The same thing with the red. It shrinks nicely just right around those wires. If you focus too long on one side, you’ll end up melting and burning a hole through the heat shrink, damaging the wire. Let those cool down.

To test it I’m going to use my split-phase dryer motor here and I’m going to locate contacts four and five on the motor which are used to start the motor up. I’m going to connect my line voltage to one of the contacts, my neutral to the other. I’m going to take my ground, I’m going to attach that to the motor itself. Locate a 120 voltage supply, make sure you’re holding down the motor when you go to start it up and turn the power on and the motor should run.

You can see just by using this 120-volt power supply tester, we can apply power to any component to make sure that it’s actually the component that’s a failure or it’s not. If a dryer didn’t want to start, we would actually see right there, it’s not the dryer motor. We’d have to look somewhere else. This is something that’s really easy to make, something that’s going to make your life a lot easier in the field. I hope you like what you saw. I hope you guys enjoy making this tool. Again, everything’s in the description below of what you’re going to need.

If you really like everything, like, subscribe and keep an eye out for some extra videos out there that we’re going to be bringing out. I’m Tim, with Fred’s Appliance Academy, where we’re training tomorrow’s technicians today. (music)


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