Coleman Mach Air Conditioner Not Cooling? Try THIS First
May 30, 2024
If your RV's air conditioner is blowing air but it's not cooling the air at all, then today I'm going to give you a quick and easy test that almost anyone can do, that is going to tell you with 99% certainty whether or not your air conditioner itself is still okay. Because I know that's everybody's biggest fear - the air conditioner stops blowing cold and they're worried they're going to have to replace the whole unit. This is the test that's going to tell you if you have to replace the whole unit. It's very exciting!
All you're going to need is a multimeter, and it can be the cheapest multimeter on the planet. Any multimeter that you buy is going to have the test that we need today. And if this already scares you, you're getting PTSD flashbacks to that one mean science teacher you had in high school, have no fear. We're going to banish those memories away. I am not your evil high school science teacher. I am your friendly neighborhood RV repair tech. Hi! Hello! My name is Emily. I am a certified mobile RV repair tech based in Las Vegas, and this is RV Repair Woman. So let's jump on into it.
The first thing that you are going to do for this test is to actually flip the breaker for your air conditioner. One of the great things that I love about this test, and why I love having it be one of the first things that you try out with your meter if you haven't used a meter in a while, is that we are going to shut off power to the thing that we are testing. So we are lowering the chances of getting shocked or interacting with electricity in a way that we don't want to, drastically. Which is great. Love that.
Fun Fact: I used to run obstacle course races. That used to be my side hobby. And one brand of them, their cool, differentiating factor was that they shocked you with like 10,000 volts or something like that, as one of the end obstacles. And I freaking hated it. Oh my God, I was screaming the whole time. Hated it. I would do almost anything to not get shocked like that again.
Which is why I love this test. Almost no chance of getting shocked. And we're going to double-check the shock factor before we touch anything. So we're going to take the chances of getting shocked from like 1% to 0% there, which is great. Alright, so we have turned off power to the air conditioner entirely. Yay!
The next thing we're going to do is hop up on our roof. Now, if you're like, "Emily, these knees haven't seen the top side of a ladder in years," don't worry. I understand. I am able-bodied of mind and spirit, and I have days where I don't wanna go up on a roof. Find somebody who is young of knee, walk them through this test, then bake them a cookie after. You would be surprised what young people will do for a good baked good. And this test is so simple that you can walk almost anyone through it. Okay? So you can make a friend in the process. How exciting! It’s so hard to make friends as adults. I'm giving you the way. This is it!
So either you or your friend with good knees is going to go up on the roof. They're going to locate your air conditioner. It's going to have a cover on it. The cover's going to look something like this. If you have a Coleman mock air conditioner, that cover is going to have four screws on the top. If you have a domestic air conditioner, there's going to be four screws along the side. Unscrew the 4 screws, shimmy that top off. On these Coleman mock air conditioners, I find that cover kind of tricky to get off. Just give it a little shimmy action. It will happen. I don't love the design of these for getting that cover off. Dometic did a better job on that.
Either way, alright, we got the cover off. Over here we have the fan. That's what moves the air.
Over here, we have the sort of black cylinder-looking thing. This is the compressor. This is what cools the air, okay? We're going to test the compressor today because I'm assuming with your air conditioner that the fan's working great. The fan's moving the air, it's just not getting cold. So let's see if the compressor is the culprit.
What you're going to do is you're going see that there is this cap on the compressor. There's a post right about here, there's going to be a nut on there. Unscrew that nut and this cap's going to come right off. If you have a Klein 11 and one, that multi-tool that I brag about all the time about how much I love, one of its many different tools is going to get that nut off.
Okay, so back to the compressor. Now that we've taken that cap off, you're going to see we have two different parts here. Now I am touching things right now because my air conditioner is not plugged in anywhere at all. So I know 100% there's no power going to this air conditioner. You are not going to start touching anything until we do our test to be 100% sure that there is no power going to this air conditioner. But just for show and tell, I'm going to touch it because I can.
On the right, we have what's called the heat overload. If you’ve followed a lot of my troubleshooting videos, almost every appliance in your RV has a part that is very similar to this heat overload. So on the water heater, we're talking about like that Eco and the t-stat, if you've seen that video. If you've watched my fridge video and you heard about the Thermal disc or the Thermal fuse. Or you've watched any of my furnace videos and heard about the high-temperature limit switch, all of those do the exact same thing. They are switch that is normally closed, so it normally lets electricity through. And then when something gets too hot, it pops open and shuts everything down. That is all of that heat overload is doing. It is looking to see if this compressor is getting too hot and if it does, it shuts everything down too. You can test it with continuity. We're not going to go too deep into that today because we're trying to keep things simple and to the point, but just a little extra bonus tip for my people that have been following along and know how to use their meters.
Okay, back on the compressor. These are actually the terminals for the compressor itself.
You're going to look on your meter for the section labeled ACV, which stands for AC volts. If you've watched my other electrical videos, you know there's two types of electricity in an RV, AC and DC. The compressor on your air conditioner uses AC power. So if you have a cheap meter like this, it is not auto-ranging. It does not know if you're looking for a large amount of electricity or a small amount of electricity, so you just need to tell it roughly how much AC voltage you think you are going to see. In an RV, when it comes to AC volts, the number that we're always looking for is around 120, the same voltage that comes out of your outlets in your house or the outlets in your RV, for that matter. So if you look on my simple meter under ACV, it has two different options, either 200 or 600. We are going to choose 200 because that's the closest number to 120. We're just telling the meter we're going to see an amount of AC voltage in the realm of 200.
Alright, so I'm set to test AC volts. You're going to take one of your probes, put it on one of the terminals of the compressor. You're going to take the other one and touch any metal part of the air conditioner. Then you're going to touch a different terminal on the compressor and short it to the metal part of the frame, also looking for zero. And then the same thing with the third, still looking for zero. That is going to tell you that there is no power going to this compressor, which is great. That's a good thing. That's going to tell us that we can touch the compressor without getting shocked.
There shouldn't be any power going to that compressor because we threw the breaker. But on my first-ever air conditioner call as a tech, I did exactly that. I threw the breaker for the air conditioner, I went up on the roof to do this exact test, and shocked the crap out of myself because it turns out that that RV was wired backwards and the breakers weren't actually doing anything or protecting anything, and they didn't protect me that day. So I learned my lesson on my very first call. Always double-check that there is indeed no power going on towards your touching before you put your meat fingers in the places where electricity might be.
Then we are going to take some needle-nose pliers and we are going to take off all of the connections on this compressor.
Bonus tip: you may wanna take a picture of the wiring before you do this so that way you can rewire it up after if it turns out that your air conditioner is fine.
Alright, we now have a beautiful compressor just hanging out living its best life, ready to be tested.
Emily, how do we do that test?
We're going to set our multimeter to a different setting. We're going to set it to resistance. On the simple multimeters, you're looking for this ohm symbol. It's the one that looks like a Greek letter, you might remember it from fraternities and the like. And again, you're going to have to tell the meter if you have a simple one like this roughly how many ohms we're looking for of resistance.
Resistance, as a quick reminder, is the number that we use to represent how difficult it is for electricity to move through a substance. So a wire that's just hanging out living its best life should have a resistance close to zero. It should be very easy for electricity to move through a wire, whereas a hunk of wood, for instance, should have a much higher resistance.
Okay, so we're going to see if the resistance of this compressor is a number that makes sense and I'll tell you what makes sense means in just a minute, but if the resistance is too high, that's going to tell us that this compressor has gone bad. On this meter we're going have to tell it roughly how much resistance we're looking at. The numbers that we're going to see here are all going to be 10 ohms and lower. So on this meter, I'm going to set it to 200 because that is the smallest number available to me there, but if yours had 20, you would set it to 20 and then you'd be ready to go.
Over to the compressor.
You have your two probes. You're going to put them on two of the posts on the compressor and you're going to get a reading. Right there it says 1.1.
You're then going to touch two other terminals and get a reading there, that's 2.6.
And then you're going to touch the last combination of terminals and I got 2.9. Go ahead and write all of those numbers down that you got.
If I lost you anywhere in there, there are three terminals, we'll call them a, b, and c. So you're going to test across a and b, and then a and c, and then b and c. So every combination of pairs that we can across the three, we're going to write all of those numbers down.
Now we're going to have to do just a smidgen of math. Do not get nervous here, don't be afraid. I've got a tool for you if mental math is not your strong point. It sure as heck ain't mine.
So if you are good at mental math, what you're going to do is just add the two smaller numbers together, and they should equal the largest number, plus or minus about 10% tolerance in there.
Doing that math when you're up on a roof and it is hot outside and you're sweating and the answer to this math is going to tell you whether or not you need to replace an expensive air conditioner on someone's RV can be a little nerve wracking, which is why I made a quick and easy tool to help me.
Literally all you have to do is put the three numbers in the three boxes and it will tell you if your compressor is good or bad. Its that easy and it takes the 10% tolerance into account.
I do this all the time and I still use that little spreadsheet because it makes my life easier. I don't have to worry that I did a mental math error and now all of a sudden somebody needs to spend $1,200 that didn't need to.
Bad Compressor
If your compressor is bad you’re unfortunately look at a new AC. The compressor is the only electrical part on your air conditioner that is that is not replaceable.
Everything else, the capacitor, the control box, the thermostat, freeze sense, heat overload, all of that, we can switch out really easily and really quick. But the compressor is hard piped in you can't change them out.
You're going to get some dude bro on Reddit saying that he did it in some backwoods somewhere. It is not the standard practice. Your tech is not trying to screw you over by saying they won't switch out the compressor. There's EPA guidelines in there. And the time, and the money, and the cost of the compressor, we could not even do that switch out for less than the cost that it would be to get a new air conditioner.
So if your compressor is bad, you're looking at a new AC.
Good Compressor
If your compressor is good, then it is most likely that the reason that your air conditioner is not cooling is a very easy thing to switch out and is even easier to test than the compressor. For the compressor, we had to do some math, we had to add two numbers together, see if they equal the third, we had to do, you know, some pluses and minuses in there, it was a little nerve wracking for a minute.
Almost everything else on the air conditioner, there's no math involved and you're just using the voltage test just to test if voltage made it into a thing and out of a thing. If you would like to be able to test every part on your air conditioner step by step with a mobile tech in your back pocket walking you through every step of the way, I've created a series of pdf guides that are going to help you diagnose your air conditioner all by yourself.
Right now, I just have them up for Coleman Mach. I have one for if your air conditioner will turn on, but it's not cooling. And I have another one that's going to be released any second now that is for if the air conditioner won't turn on at all, where we track down the fan and figure out why that's not turning on.
Dometic people, do not worry, I've got a Dometic air conditioner sitting on my floor waiting for me to take pictures for it, your guides are coming, I promise.
These guides are so much cheaper than any tech that you're going to call - like 1/10 of the cost. You get to do the work yourself, so you don't have to worry that some unscrupulous tech is telling you that your air conditioner needs to be replaced when really it was just the heat overload.
And my ladies, I see you out there, I hear you, I talk to you all the time. You are nervous about calling a male tech and having them come in and talk down to you and tell you all the things that you're doing wrong in life. I understand, there's not enough of us female techs out there. Become your own tech, be your own expert. No one can talk down to you when you're solving the problem yourself.
And you'll have me with you every step of the way with these guides. You can find them at RVRepairWoman.com/ACGuides. Check those out, I think they can really help out a lot of people, stop trying to dig through YouTube University and hope you can find someone with the answer.
I walk you through everything that you need to know, you got this.
The 1%
If a little part of your ear picked up in the beginning when I said that you would know with 99% certainty whether or not the air conditioner needed to be replaced, one, you're very observant, two, I still got you, I wasn't trying to trick you.
Short of you going under a bridge that was too short and ripping this thing off of your roof and denting the crap out of it, there's really only two reasons why an air conditioner unit needs to be replaced.
One is what we just tested for, if the compressor is bad. The other is if you have a refrigerant leak or refrigerant blockage. Unfortunately, leaks and blockages we cannot fix.
I don't recommend, as a tech, that you have someone recharge your AC. I have a whole video on why I don't recommend them for fridges. The reasons are very similar for air conditioners. I will be coming out with a video, probably next week or the week after, about a test that you can do to test and see if you are in that 1% of people that have a refrigerant leak.
Refrigerant leaks supposedly only account for 1% of air conditioner calls. I say supposedly because I have not done over 100 air conditioner calls in my span yet, and I've had, I want to say like 3 that had refrigerant leaks - these were obvious. This was not me misdiagnosing something.
I don't know if we just have more of them here in Las Vegas or if I just have an abnormally high number because we just are on the extremes of what these air conditioners are supposed to do here in Las Vegas, but I have seen higher than that 1%.
It is still extremely, extremely low. Refrigerant links are not common and they're pretty obvious most of the time when they do happen. You're going to see a black oily like substance either on the ceiling inside your RV so around that access panel for your air conditioner, you'll see like a black oily substance along the ceiling or up on your roof right along here, where the air conditioner is. That black oily substance is the go-to sign that you have a refrigerant leak.
There is a test that you can do with your multimeter to see if you have a refrigerant leak. It does involve having a meter that has an amp clamp on it which isn't something that you find on these super cheap meters. But I have a video coming out soon on how to test that so you can test to make sure you're not in that 1%.
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But if your compressor is testing good you can know with 99% certainty that your problem is upstream and that's a super good thing that you want to see because it means you can solve that problem by yourself real quick real easy to change out and we can get your air conditioner back up and running real soon.
I think that is all for today. In the meantime, please consider hitting subscribe. I put out videos like this on the regular giving you the RV tips and tricks that most techs don't want you to know. I'm trying out a new kind of format here, trying to find a way to get these videos out as my business gets busier and busier.
Summer is coming, that's when I am just trying to crank out as many calls as I can during the day because that's the busiest time of year here. Which is why we're trying something out with the multi cams and seeing if we can't get these videos out consistently for you.
My name is Emily, this has been RV repairwoman, YOU GOT THIS!