HVAC Technical Academy
Sanford, Florida
May–June Session

Hello. My name is Michael McNichols. I’m at HVAC Technical Academy. Today, I’m going to be talking about capacitors.

Essentially, what capacitors are, they’re your third leg for a motor. And what that means is that you’ll take that L1 and L2 from your contactor and then that goes in. That powers it up. And you still need that little bit of power left. And that’s where capacitors come in.

All right. If you come over here, you’ll see this panel’s already been taken off. Thank you to whoever took this off for me.

As you can see, the capacitor will be essentially just against the side. Now, if you look at this one, you’ll see all this corrosion up here. Not good. Not good at all.

So, when you see this, usually it could still work, but probably save your chances and just replace this one.

Now, I’m not going to take this one out. This is not my unit. So, I brought two capacitors with me to run through, see how they work, test them, and tell you how they go bad.

Now, when you’re looking, measuring capacitors, and testing capacitors, you want to make sure before you do anything, make sure you look at this top lip over here. Make sure it’s not bubbled up or it’s not going over to the side.

You see how everything is laid in flat, hermetically sealed as it’s supposed to be because it’s a capacitor, right?

So, if your capacitor looks normal, you’re good to test.

Now, before we test, you take your voltmeter, set it to microfarads because that’s what capacitors are measured in.

All right, you’re going to take one probe. For this one specifically, if you look underneath each terminal, you’ll see that some of these are engraved with what terminals go to what.

So you’ll see it’ll have HERM, C for your common, and FAN for your fan.

So when we’re measuring, you want to keep note on the label. We’re looking for a high of 45 and a low of 5 with a tolerance of 5%. That means it can go up 5% or down 5% and it’ll still be fine.

Right? So we’re going to take one probe. We’re going to put it on our common. We’re going to take our other one. We’re going to put it on our HERM.

And we’re going to look at what our device says. Our metering device, or voltmeter if you’re technical.

And you’ll see that our common to HERM gives us 43.4, which is still within range of our 45 high, which is good. This capacitor is still good. Halfway at least. We still have to check that fan.

So, same thing as before. You take one terminal, common, find your fan terminal, and give it a second. If it’s good, it’ll give us somewhere around five.

As you see, it reads 4.84. Still within range. So this capacitor is still good. Hook it up and it’ll be fine.

This one, a motor capacitor, or run capacitor as some people call them. I’ve heard them be called run capacitors.

As you can tell the difference, this one is bigger. Much bigger.

This one you’ll find hooked up to your motors, air handler blower motors mainly.

So you see this one’s easier to test. As we look through the characteristics, still flat, not bubbled, not oval. So this is still good.

When we test, there are only two terminals. We have two probes and it gives us 79.8.

And if we look at the label, that is an 80 microfarad capacitor with a 5% tolerance.

This capacitor is still good.

And that’s all you really need to test your capacitors and change your capacitors. Capacitors are really easy, one of the low-hanging fruit in HVAC.

Pretty simple. Pop them in, pop them out. Make sure your wires are taken care of. Make sure they’re all wired in place.

And with that, we’re all set.

My name is Michael McNichols. Thank you for learning with HVAC.