Today I’m talking through 2 of the most common calls I get as an RV repair tech and revealing how anyone can solve these problems themselves using 1 simple tool.

This post is actually part 4 of a 5 part series were I’m walking through 10 of the most common calls I get.

I am on a mission to save you $5000 in your RV.

Let’s jump into it.

Resistance

If you’ve been following along the series you will know that the one simple tool that is going to save you $1000’s in your RV is a multimeter.

If you’re new here, don’t be scared this test is a great place to start.

Last video we talked about continuity, this video we’re talking about its sister test - Resistance.

Unlike other tests, resistance doesn’t tell us about the electricity in a circuit, it tells us about the material the electricity is going through.

It namely how hard it is for electricity to move through that material, and we measure resistance in a unit called ohms.

So, we would expect a wire to have a reading pretty close to zero ohms because it's purposely very easy for electricity to move through a wire.

Whereas we would expect a hunk of wood, for instance, to have a close to infinity resistance reading because electricity doesn't like to move through dry wood. That's why we don't use it in circuits.

If we go back to our car metaphor from the continuity video, are the cars driving easily through air or are they driving through jello?

The different between continuity and resistance is that continuity is a binary where as resistance is a spectrum.

The manufacturer of the meter chooses one resistance reading, and I believe for the Klein CL800, it's 50 ohms.

So, they decide any reading under 50 ohms means that electricity can move through this material just fine, whereas any reading over 50 ohms means that electricity can't move through this very well.

So, any reading under 50 ohms has continuity, and any reading over 50 ohms does not have continuity.

This is why I gave you that work around last video if you didn’t have a continuity setting on your meter.

Sometimes, we wanna measure the actual resistance of a component in a circuit to see how well it's functioning, and other times, we just need the binary, "Can electricity move through this or not?”

Oh and by the way if you’re madly taking notes. I see you I love you. You can also just head over to RVRepairWoman.com/5000 and I have a workbook that will show you how to set up your meter for each test and walk you through all of the 10 calls in this series and how to solve them yourself.

Meter

So how do we set up our meter to test resistance?

On the words cheapest Harbor Freight meter just look for the section with the Ω symbol. And the 200 setting should be fine for anything in your RV.

On a fancier meter just look for the Ω symbol and use the orange button to toggle between resistance and continuity.

And just like continuity, when we are testing for resistance we want there to be no electricity going to the thing we are testing.

The way your multimeter tests for resistance is it sends a small amount off electricity out one probe and sees how much makes it to the other probe.

If there is any other electricity happening in the circuit it can mess with the reading that the meter gets.

So when we test for resistance we always disconnect the thing we are testing from the circuit entirely.

This is why this is a great test to start with because you’re very unlikely the shock yourself.

And now you’re ready to poke around with your probes.

Call 1

ring ring

Me: Hello?

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

Me: I’m on my way!

If your AC is turning on but not cooling there is a chance that your compressor has died. That is the part of the AC that moves the refrigerant around.

To test if this is the case turn the AC off at the thermostat and throw the breaker for the AC.

Then head to your roof.

This test works no matter what brand of air conditioner you have.

So take the cover off of your AC and locate your compressor - its the black cylinder looking thing.

It should have its own cover on the top that comes off with just one nut.

And when you take that cover off it should look something like this.

You can double check that there is no power going here if you want by using our AC voltage test from the other video and testing from each terminal to the case. You should see 0V.

Then take a picture of how everything is wired so you can rewire it up later.

Then disconnect ALL of the wires going to the compressor.

You should see three terminals and if you look very closely, they should be labeled C, R and S.

You’re going to take your meter, set it to resistance, and measure across every combination of those three terminals.

So across C and R, R and S, and S and C. Write down all three of those readings.

Then we do need to do just a little bit of math here. Don’t worry I’ve got a tool coming up that can help you if math not your strong point.

You’re going to take the two smallest numbers and they should add to the largest number with a tolerance of plus or minus 10%.

So if our two smaller numbers were two and three, we would hope that the largest number was between 4.5 and 5.5.

If that math is a little tricky for you to follow and I totally understand. It can be hard to do this math especially when you’re on a roof and whether or not you have to spend $1000 on a new air conditioner is on the line.

You can head over to rvrepairwoman.com/compressor and I have a quick and easy tool that will help do this math for you.

You just pop in the three numbers and it will show you in a big bold font whether or not you compressor is good or not.

You got this.

Call 2

Me: Hello?

Customer: Help! Help! My fridge is working on propane but not electric!

Me: shrugs

If your fridge is working on propane, but not on electric, then there’s a chance that your heating element has gone bad.

Set your meter to resistance and head to the back of your fridge.

If you look on either side of your fridge, there should be a sheet metal tube.

Inside of that tube is going to be your electric heating element. Your electric heating element is actually how your fridge gets cold when it’s on the electric setting.

Inside that heating element is essentially just a big resistor.

A resistor is just a material that is very hard for electricity to move through.

When electricity has to start working really hard it creates a lot of heat.

So we can measure the resistance of this heating element to see if it’s still good or not.

You don’t have to take the heating element out of the tube that’s actually kind of difficult to do sometimes. Just follow the wires back to the circuit board and unplug them.

With your meter set to resistance, put one probe in one terminal for the heating element, and the other probe for the other terminal on the heating element You should get some kind of resistance reading.

You can Google your brand of fridge and “heating element resistance” and it should help you bring up what that resistance reading should be at.

But for the most part when these heating elements fail, they actually break inside, so if you’re getting a resistance reading that says something like 0L that means that the wire inside of the heating element has broken.

Essentially we don’t have continuity anymore if we remember that test from the last video.

So if the wire inside of the heating element breaks the heating element is bad. Switch it out you should be good to go.

My calculations are now up to $4500 that we’ve potentially saved in our RV if you would like to learn how to save that last $1000 that’s right I actually gave you an accidental 11th call and this series will go to $5,500, because apparently I can’t count to 10, check those out the next video in this series here.