Want to save major moolah on RV repairs? This video is the last part of a 5 part series waking RVers through the 10 most common calls I get as a certified RV repair tech, and revealing how anyone can solve these problems themselves with just a multimeter.

My name is Emily and this is RV Repair Woman.

So we’ve gone over the volts AC and DC test, continuity, and resistance. So today were doing the amperage test.

While the voltage test tells us where the electricity is in a circuit, we use amperage to tell us how hard an individual component is working in a circuit.

So, if you remember back to the voltage test, there's going to be a value that we expect to see. It's either gonna be 12.5 if we're on the DC side of things or 120 if we're on the AC side of things.

When it comes to amperage, we're going to get our expected value from a tech sheet that the appliance comes with.

So, I can pull up the spec sheet for your appliance and see what amperage different components in it should be pulling. And I can compare that to the amperage reading of what I actually see.

If the amperage reading is significantly higher or lower than the value that is expected according to the spec sheet, then we know that something is wrong and we can act accordingly from there.

And just like voltage there is an AC amperage test and a DC amperage test.

In RV’s we rarely if ever use the DC amperage test.

(I’m going to get people in the comments going WHAT ABOUT THIS? Yes there are niche scenarios, but the AC amps is used FAR more by RV techs than the DC amps test.)

Remember how I told you the DC was the brains of the operation and the AC is the muscle?

Because the amperage test is the test that tells us how hard things are working, we usually care about it more on the muscly AC side of things.

So, how do we test for amperage using our multimeter? Well, this simple meter actually doesn't allow you to test AC amps. It only has a DC Amperage setting.

If you end up in some niche scenario where you need it, we're gonna be looking at this section here labeled DC A for DC amps. And again, we have to tell this meter, because it's not very sophisticated, roughly what range of amperage we think we're going to see. If you’re on a very cheap meter like this one, set it to the largest setting it has.

On my fancier meter I turn the dial to the A setting and use the orange button to switch between AC amps and DC amps.

testing

So, how do we actually test for amperage?

Running an amperage test with your probes on your multimeter is actually something that I don't do very often.

Unlike with the voltage test where we could just leave the circuit as it was and then just poke and prod in with our probes to run an amperage test, because we're trying to read the current going through the wire, we actually have to have our meter in line with a component in the circuit.

If we think of your circuit like a bunch of people holding hands, if we were to test the voltage across one person, we could put one probe on each side of a human and read the voltage going through that human. This is a metaphor, stick with me.

In order to read the amperage, we would need two people to let go and stop holding hands, and then put our meter in between those two people, and then have one person on each side hold the probes, and then we could read the amperage going through the whole line.

What this looks like in real life is if you wanted to read the amperage with your probes, you would need to disconnect a component from the circuit, and then put one probe onto the terminal that you just disconnected from, and your other probe into the thing that you just disconnected. You can see we are recreating the connection that we just disconnected with the meter in between.

But as I hope that you're able to sort of see with this, in order to get the probes where they need to be can be really difficult without shocking yourself because there is live power going on.

And then you have instances where several connections all come into one clip, like on this 9-pin connector in an air conditioner. There'd be no way that I could just disconnect, one of these wires from that 9-pin connection, and then get my meter in there.

This is why I basically never run an amperage test with my probes. It's just a pain in the butt.

When I run amperage tests I use the amp clamp on my meter.

To use the amp clamp, all I need to do is set my dial to amps. And then, I put this adorable little mouth-looking part around a wire that has power going through it. The internal computer in the multimeter is going to use a really cool property about electricity.

When elecriticy goes through a wire it creates an electromagnetic field. The meter is going to read that electromagnetic field and do some math to tell us the amperage going through the wire is.

This is so much more useful because I don't need to disrupt the circuit at all and unplug things. I can keep everything just the way it is, and then just wrap around whatever wire I need to test.

Remember you can go to RVRepairWoman.com/5000 and get a workout that is going to walk you through not only how to set your meter up for every test, but also give you a cheat sheet for each and every one of the 10 calls in this series.

ring ring

speaking of

Call 1

Me: Hello

Customer: Help! Help! My AC is turning on but not cooling!

We got this!

This is a fun and super easy test anyone can do with AC amps test as long as your meter has an amp clamp.

Head to your rooftop AC unit find the compressor.

Locate the black wire coming off of the compressor if you’re on a Colman AC or the blue wire if you’re on a Dometic AC.

While the Air Conditioner is running and set your meter to AC amps and put your amp clamp around this wire.

You should get an amperage reading of some sort.

Now Somewhere on the side of the rooftop unit should be a sticker with technical information. You are looking for the RLA for the unit. Don’t get it confused with the LRA, that’s something different.

Compare the RLA on the tech sheet to the amp reading you got from your meter. Adjust the RLA reading on the tech sheet according to how hot it is outside.

For a Coleman we’ll go up or down 1 amp for every 5 degrees from 95ºF it is outside.

And for a Dometic we’ll go up or down 1 amp for every 10 degrees from 95ºF it is outside.

If the reading you go on the wire is drastically different from the reading the table says you should have than you either have a bad compressor or a refrigerant leak. Both mean that you need a whole new AC unit.

But at least you diagnosed the problem yourself.

Most mobile techs charge for both the diag and the install because both take time. So you’ve saved yourself the diag charge.

Call 2

ring ring

Hello?

Customer: Help! Help! My AC is humming but it won’t start!

Me: I’m on my way

If you’re AC is aggressive humming noise but won’t actually start up, that’s a classic sign of a bad capacitor.

Here is how to double check and find out using our AC amperage test.

Go back to that same wire that we talked about in the last call and look at your meter as that humming noise is happening.

If it looks like the reading is going all over the place like it tries to ramp up and then immediately comes back down to zero and then tries to ramp up and then immediately comes back down to zero then that is a classic bad capacitor.

The capacitors job is to provide some extra oomph during start up to help get the air conditioner going. But if the capacitor doesn’t have enough juice in it, then it can’t get the AC started.

So what you’re seeing on the meter is that capacitor tried to open up and then not getting there and coming back down and then trying to give it a push and not like getting there and coming back down.

I’m going to have another video coming out soon that’s not a part of the series about how to safely discharge and test the capacitor if you decide you actually want to solve this problem yourself but you have at least diagnosed what was wrong entirely with just the AC amps test on your multimeter.

You now know how to run the AC voltage test, the DC voltage test, resistance, continuity and amperage on your multi meter.

You know how to solve the 10 most common calls that I get as tech.

You now have the basics behind what every RV tech is doing when they come to try to diagnose something in your RV.

So what’s next?

If you would like to know step-by-step, how to diagnose any appliance in your RV head on over to rvrepairwoman.com/rvacademy.

I’m gonna be putting on a live four week class starting July where I’m gonna walk you through step-by-step how to diagnose any problem that occurs with your tanked water heater, your absorption fridge, your furnace or your air conditioner.

You’re basically gonna learn in one month how to become your own personal RV tech.

We’ll meet every Monday for a LIVE video class from me where I’ll go over the appliance of the week and you can ask your questions in real time via chat.

And if you can’t make Monday’s I totally get it… Don’t worry you’ll get 6 months access to all of the replays so you can watch over and over again at your own pace.

And you’ll have access to a private community of just other RVers going through this course where you can ask your questions there and get them answered by me or by other awesome people who are learning along with you.

There’s also a ton of other awesome bonus’s.

I don’t know if I’ll ever get the chance to run this course live again. I am really busy fixing people's RVs IRL right now. So if you want to get in on this class now is the time.

Again that’s at rvrepairwoman.com/rvacademy you can learn more about it, see if its the right fit for you.

I’m super excited to get to meet some die hard RVers who want to be able to handle anything their RV throws at them. 

I’d love to see you there.

- Emily your RV Repair Woman