The camping world near me currently charges a $500 minimum for mobile rv repairs. Which isn’t even the highest I ever seen. And is bonkers when you start thinking of how often things go wrong in RV’s and the fact that with one pretty simple tool you can solve almost any RV problem yourself.

My name is Emily, I’m a certified mobile RV Repair tech.

And this post is actually the first in a five post series where I’m going to reveal the one tool that is going to save you $1,000’s in your RV. And then show you 10 most common calls I get as a tech and give you the step by step framework to solve those calls by yourself by harnessing this tool’s epic power.

This is RV Repair Woman.

Secret Tool

So you may be wondering what is this one tool that is going to save my dying wallet and make me look like a greek god to my family, and have crowds of people cheering my name?

Well if you’ve been around the channel for awhile you’ll know its a multimeter.

But if as soon as this thing came on screen you got PTSD flashbacks to your horrible high school physics teacher do not be alarmed.

This guy is not as scary as he seems.

If you can turn a door knob and hold two pencils you can use a multimeter.

And if I were stranded in an RV on a desert island and could only have 1 tool, this is the tool I would want to have.

If you can over how scary he may look on the outside and start using one of these bad boys you can save yourself some major moolah in your RV.

Let me show you how.

Dc Voltage

We’ll eventually go over most of the tests on your meter and how to use them across the five video series, but today I’m going to concentrate on my #1 most used setting, and how you can use it to solve 3 of the most common calls I get as an RV tech.

That setting? Dc Volts.

People who’ve taken RV Basics to Badass (my free RV beginners course) will know that there are two types of electricity in your RV.

AC and Dc.

Today we’re just going to talk about Dc volts, we’ll hit AC voltage in the next post in the series.

Basics

So think about electricity as bob the electron going one big circular journey.

And the voltage test is going to be the test we use to check in on bob and see where he’s at on his epic quest.

Bob is trying to go over a mountain and through the woods to grandmothers house. But if he goes into the woods and never comes out then we know the woods is the source of our problem.

Same goes for a circuit.

If we can confirm that bob made it into a thermostat for instance, but never came out, then we know the thermostat is the source of our problem.

Solving electrical problems can be that easy.

But how do we test for voltage? How do we find Bob?

Well if you have a simple meter like the cheapest thing you can get from harbor freight you’re going to look for a section like this labelled DCV for DC volts.

Because this meter isn’t very sophisticated we need to tell the meter roughly what range of Dc volts we expect to see.

When it comes to RV’s our main source of Dc voltage is our batteries and they come in at around 12.5 V. So that’s usually what we’re looking for.

So we’re going to set our meter to 20 because that’s the closest number it has to 12.

On my Klein CL800 I can just set the meter to the V section and then hit the orange button to toggle between AC volts and Dc volts. Look for the squiggle for AC and the straight line for DC.

My Klein meter (along with most fancier meters) is auto ranging. Meaning I don’t have to tell it if we are looking at a small amount of voltage or a large amount of voltage. It can automatically detect that itself and is going to change its unit depending on whether I'm looking at millivolts or volts.

That does mean that we need to keep an eye on the unit when we are testing voltage. As a general rule of thumb, any reading of a milli-anything in an RV is too small for us to care about. Whether that be a millivolt, a milliamp when we talk about amperage later, or milliohm when we talk about resistance later.

We're just not doing anything so sophisticated that we need to care about a reading that small.

Then, to actually test for voltage, we need to plug our probes into our meter.

Now, we're ready to test voltage around our RV.

One thing we need to keep in mind when we're testing for voltage with a multimeter like this: we're actually testing for the difference in voltage across our probes. This sounds a little in the weeds, but stick with me.

As a metaphor, think about if you were to measure my height standing on the floor, I'm about 5 foot 3. But if I were to stand on a bench, I would be roughly 6 foot 3 if we measured me from the floor. If we measure me from my knees, even if I’m standing on a bench I might be closer to 4 foot 3.

So, when it comes to measuring people's heights, we have all decided on a common place, the ground, that we're gonna measure their height from. When it comes to voltage, we need something similar, and in electricity, we call this place either the common or the ground.

A lot of the times, when we're measuring voltage, we're actually gonna put our black probe on the part of the RV's frame so that can be our ground that we're gonna measure the difference in voltage off of.

This can look like a couple of different things: either finding a metal part of the RV frame to put your meter directly to, or a lot of times in appliances, there'll be a bunch of wires that all go to a metal screw that's drilled into the frame.

We can put our black probe onto that to guarantee that we're on the ground. And then, we usually use our red probe to poke around in different parts of the circuit to find Bob.

If you’re madly taking notes right now you are an RVer after my own heart, but please just know if you head on over to RVRepairWoman.com/5000 I have a free workbook that will walk you through not only the tests on your multimeter but also how to work through step by step all 10 of my most common calls if you want to get a jump start on the video series. RVrepairWoman.com/5000 You Got This.

Okay now that you’ve got your meter up and running let’s go on some calls.

Call #1

Customer: help! help! Nothing in my RV is working! I think the batteries might be dead.

If multiple things in your RV aren’t working then there is a good chance your batteries might have died. Here’s how to use our new Dc volts test to find out.

Set your meter to DC voltage, unplug your RV from shore power, and keep some lights on in the RV so we still have a load on the system.

Go find your house batteries and place your black probe on the negative terminal of the battery and your red probe on the positive terminal of the battery.

If you have lead acid batteries and they're fully charged, you should be seeing a reading in the realm of 12.5 Volts.

Anything under 12 volts is technically considered a dead battery.

Usually if I see a reading that still above 8.5 I’ll try to recharge the battery and see if it will hold a charge.

But if you’re getting a reading below 8 that battery is definitely dead and needs to be replaced.

Now while you’re here - Bonus activity: if your batteries were good keep your red probe on the positive terminal of the battery, and take your black probe and touch it to a metal part of the frame. You should still see 12.5 V.

This is because if you were to follow the cable coming off of the negative terminal of the battery, it would eventually lead to a screw that is either bolted or screwed into the metal frame of the RV.

That way, no matter what, the frame can act as our ground for all of our appliances.

Pretty cool.

Now go ahead and put both of your probes on the positive terminal of the battery. Now, you're gonna see 0 volts, even though the batteries are charged. We just tested that.

And that's because we're measuring the difference in voltage from one probe to the other. So, now that they're at the same point, there is no voltage difference.

That's why the concept of finding your ground is so important.

But that’s all I’m doing when you call and say you think you have a dead battery. I’m setting my meter to DC volts and putting one probe on each terminal and looking for 12.5 volts. That’s it.

Will that be cash or credit?

If we think things are seeming fishy I may keep the RV unplugged for a couple minutes with the lights still on, and see if the battery can hold that 12.5 volts for a bit while under load.

Sometimes if that battery was just plugged into a charger it can say 12.5 because it was just being charged, but it can’t actually maintain it.

If it can’t maintain its a dead battery.

That charger that was making things seem fishy? ->

Call #2

Customer: Help! Help! I’m plugged in but my fridge won’t turn on! Little Timmy’s chicken stew is going to go bad!

So even though the DC power in your RV powers multiple appliances like your lights your slides and your leveling jacks - usually the thing that people notice first when the Dc power goes out is the fridge.

I can’t tell you the number of calls I’ve had where the initial call was for a bad fridge but it was actually that there was no DC power for the whole rig.

You already know how to check the batteries. But if you’re plugged in there should be something called a converter kicking on to charge the batteries.

You converter just takes the AC power that comes from the pedestal you’re plugged into and changes it to DC power to charge the batteries.

Its just like a fancy battery tender you might put on your car battery if you’re going away for awhile.

If you’re plugged in and not getting Dc power anywhere then there’s a good chance your converter is acting up or has died. Here’s how to use your Dc voltage test to find out.

I usually start by testing at the batteries because they are the easiest thing to get to.

While the RV is plugged in this time, set your meter to Dc volts and put one probe on the positive terminal and one probe on the negative terminal. You should see something in the realm on 13.5 volts this time.

This is because the converter puts out a higher voltage than the 12.5 volts the batteries sit at.

Think of it like trying to pour water from one glass to another. In order to get water from glass A to glass B I need to have glass A higher than glass B. If glass A is lower the water isn't going to move up.

If we’re not seeing 13.5 volts at the batteries while we are plugged in then our converter may have died.

You can track down the converter to double check, its usually hiding either behind or below your breaker box panel.

When you pull that puppy out it should look something like this.

Remember if we know power goes in to something but doesn’t come out of it then that part is most likely our problem.

A lot of these converters just have a normal Edison plug on them so you can just take this whole unit, plug it into a known good outlet and you’ll know that power is making it into the converter.

Then you’ll see there will be terminals for the DC out. If you haven’t pulled your converter out completely there will be wires coming out of here that go to the batteries. That’s cool. That’s what we want.

So set your meter to Dc volts, put your red probe on the + terminal and your black probe on the - terminal and you’re looking for something in the realm of 13.5 V. If you don’t your converter is bad.

You Got This.

Call #3

Customer: Help! Help! My AC isn’t working!

A lot of people assume when their AC stops working that they need to replace the whole unit, when a lot of the time its just a bad thermostat.

Real talk I was able to talk the seller down almost a grand when I bought my RV because the AC wasn’t cooling and she thought it needed to be replaced. But I took a quick look and was pretty sure the thermostat was the actual problem.

Here’s how you can do the same.

Set the thermostat to COOL and HIGH FAN, set the temperature as low as it will go to insure that the AC should be kicking on and then open that sucker up.

Set your meter to Dc volts and put your black probe on the blue wire and your red probe on the red wire and you are looking for something in the realm of 12V.

This is the power going IN to the thermostat.

If you don’t see 12 V then the problem is upstream of even the thermostat.

If you do see 12V then put your black probe on the blue wire and your red probe on the yellow wire. You are looking for something in the realm of 12V.

This is the signal going out to the compressor (the part of the AC that does the actual cooling) to tell turn it on.

Then put your black probe on the blue wire and your red probe on the green wire and you should see something in the realm of 12V.

This is the signal going out to the fan to tell the fan to turn on.

If you didn’t see 12V on either the yellow or the green wire check the thermostat for a bad fuse, if there isn’t one then you have a bad thermostat. Switch that bad boy out and you should be good to go.

By my calculations we’re up to $1,500 bucks saved. If you want to save another $1000 keep an eye out on Friday where I'm going over the next setting on our multimeter.