How to Test a Transformer (Step-by-Step)

 Okay, in this session we're gonna troubleshoot a universal transformer, so we have to look at a few things. One is the information on the label, and we have to understand that this is a primary coil and this is a secondary coil. High voltage goes in, low voltage comes out. Now in order to test this, we're gonna test this for continuity and ohms, and I'll show you both on the meter.

So the two wires here are the wires that supply the 24 volts. So since this is out of the box or out of the system, we're gonna test it for the ohms. So first we go to mega Ohms, and we're not measuring millions of ohms, we're measuring somewhere between zero and a hundred. So we have to make sure that we hit the range until there's no letter next to it.

That means. Zero up. Okay, so since this has no power, you can touch the leads. One lead goes to each wire and we have 1.2. That's perfect. That means there's a connection. Now,

if we have this on tone for continuity, this will confirm through an audio tone that there's a connection. So this is good. However, it may have a tone and a. Doesn't have a good om reading, so we have to make sure that you do both. Okay. In this case, this is good so far. Now on the label, it will tell you which wire is common, and this is very important, and then what the different colors of the wires do.

So in this particular case, the common wire is black. Okay? So it may be white, it's usually black or white. The orange wire will be 240 volts. So between these two, this is what the 240 volts gets connected to. So I wanna make sure that this has continuity. Okay. Now this is the common wire, so it should have continuity with all of the wires, and I'll test them one at a time.

Good, good, good. Okay, now I'm gonna measure the ohms because each wire gets different voltage. It's gonna have a different reading on the winding, so. I go to oms, I hit range.

Okay. And now the common wire is black, so one lead will always go to that wire, and then the highest voltage would be orange, and that's 58 ohms, so that's good. The second highest reading would be the red wire, which is 48, so it now went from 58. Eight to 48 because the orange gets two 40, the red is 2 0 8, black and white is one 20.

So this should have a lower reading, and that's 20 ohms. So all of them have continuity on one side, and each has a higher continuity when it gets higher voltage than the one before or below it. On this side. These have continuity and the OMS are very low. You should never have continuity between any wire on this side and any.

You while you're on that side. If you do, the transformer is bad, if you get no reading at all. So say you connect it, and I'm just gonna put it here to show you on the meter and it says OL, the meter is bad, so you have to make sure that it's on here and now you have one to two ohms maybe that shows that this side is good.

If you ever see the ol reading open, that means that there's no connection and that the connection inside is broken. Same thing with this side. So it's a good idea. To make sure none of these have ohms with the other side, but every wire on the same side should have ohms. That's how you test a transformer and you can determine whether it's good or bad within minutes.