April 29

Musty Odour from AC

Car Maintenance


Mark: Hi, it's Mark Bossert. I'm here with Bernie Pawlik. Pawlik Automotive in Vancouver, BC, Canada. Vancouver's best auto service experience. 25 times voted best auto repair. 25 times best auto repair in Vancouver as voted by their customers. And we're talking cars. How you doing, Bernie? 

Bernie: Doing well. 

Mark: So someone comes to you and they say, Hey, I have this moldy musty smell in my car. What do you do? 

Bernie: What do we do? Well there's a few procedures and there's usually one thing that's causing that, and that is usually a mold or mildew on the AC evaporator core. But there's a few things we can do to fix that. First of all we would inspect the cabin air filter and replace that if there's any amount of dirt on there .We have chemical treatments we can do where we can spray a spray through the vehicle. Clean that up. Or there's an ozone treatment machine that we have, which will usually solve that kind of issue.

Mark: So why is this happening? 

Bernie: Okay. So the way an air conditioning system works is that the evaporator core, it gets very cold inside the vehicle. That's where the coolness comes in, where it's blowing cold inside the car. And in that process, it's also attracting all the moisture inside your vehicle to that evaporator core, so it gets very wet.

And you probably noticed any day when you're using your air conditioning, especially on a hot summer day, there's water that's dripping out underneath the car. That's normal. That's not a leak to be concerned about. That's normal. Matter of fact, if it isn't dripping out, that's a problem. 

Anyway, so this is how the air conditioning process works. Now, on the moisture, of course it's cold, it's moist, any particles that might get onto the evaporator core, sometimes there could be mold spores that develop into something a lot stinkier. Mold or mildew. 

If you don't have a cabin air, if a very old vehicle without a cabin air filter, of course, you're all that outside air is being sucked right through the evaporator core. Or if you leave your cabin air filter for so long, it's dirty and air escapes past it, you're probably going to get dirt and particles on the evaporator core. So that'll, again, will help create mold and mildew. 

Mark: So what's the, I guess the cabin air filter is our first line of defence to prevent this. Is that right? 

Bernie: Absolutely. And you know, you should change your cabin air filter probably every two years, three years at the most. And depending on where you drive too, I mean, if you happen to be driving down a lot of dusty roads change it more frequently. That would be the thing to do. 

Mark: So here we have some examples of dirty versus clean.

Bernie: We do. Yeah. So the cabin air filters on the left are clean, brand new. The ones on the right are dirty. And I will say that this is just sort of, that's sort of average dirt. That's pretty dirty, but we see them that are so much worse where if you see on the bottom right corner of that picture, a few leaves, we've seen some where they're completely covered with leaves, completely covered with dirt. Left way too long. 

Musty Odour from AC

So it's important to not leave them. You don't want them any dirtier than the ones on the right. You probably want to change them sooner than that. 

Mark: So what's the first step you do when someone comes in and they tell you this, what's the process that you go through?

Bernie: Well, we would run the vehicle ourselves and just make sure we can smell it ourselves. Again, as I was saying earlier, inspect the cabin air filter, first of all, and replace that. And then I would say prescribe those two treatments we talked about, the chemical process. And along with the ozone. I think doing both of them is really effective. 

You can do one or the other, but I think both is really effective. The ozone is kind of neat. You can't be in the vehicle. It's a machine that generates ozone, we run it for a certain amount of time, but after the treatment's done, you get in the vehicle, and you sit inside, it's actually smells like you're in a forest. Like it's got that charged, fresh air. It's pretty neat. 

We've had vehicles where they smell like cigarette smoke and after the ozone treatment, it's gone. And now sometimes it comes back. But. you know, initially it's got that fresh air smell. It's really pretty cool. So that's the first step 

Mark: And what if it comes back after the kind of Febreze treatment? 

Bernie: The Febreze treatment. This is much beyond Febreze, but yeah, if it comes back then really the problem is going to be the evaporator core needs to be accessed, like the actual heater box needs to be removed. The evaporator core will more than likely need to be replaced because it'll be either clogged up or it'll have mold on it that just won't come off 

So this is an example of an evaporator core. This is an older vehicle that we just worked on recently. It's a 99 Ford Expedition. This vehicle probably does not have a cabin air filter. it might. I can't quite remember the circumstance. But we were in here actually replacing a heater core and we pulled the evaporator core out and just found this thing absolutely just covered in dirt.

Musty Odour from AC

So this is how it's supposed to look. This is one side of the evaporator core. 

And then if we look at the other side, you can see that the fins are all plugged and blocked. There's dirt and debris all over the place. This is actually baked on mud. So over time, of course, dust and dirt is blown through this vehicle. This is a 25 year old vehicle now. So it's a bit of an extreme example, but dust and dirt has come in.

Musty Odour from AC

As I said, you know, this component gets wet. So as it's got wet the dirt will, you know, sometimes form into mud and that's basically baked on. So not only is this thing, of course, going to create odours, but it'll also affect the cooling capacity of the evaporator core as well, because air can't flow through it. 

Mark: So how expensive a repair is this, if it gets that bad? 

Bernie: Well, I'm just going to throw an average out there, probably two to 3,000 dollars. We're in Canada. So maybe it's less than the US, but maybe it's the same price. I don't know. But, you know, I'll just say an average of two to 3,000 dollars. Now it could be a lot more in some cars. It could be a bit less. But, you know, that's sort of an average kind of price. Most of the time the evaporator core is buried deep behind the dash.

So the whole dash has to be removed. Then there's a box that contains the heater core and the evaporator core, and that has to be dismantled and then replaced. And, of course, the air conditioning system has to be evacuated and recharged. And depending on what kind of refrigerant you have, most cars have R134A but there's a new one, R1234YF refrigerant, which is about four times the price of the other refrigerant.

So you know, it can be more costly. So depending on the year of the car and make and model, that's kind of an idea. 

Mark: If your car smells, the people to see are Pawlik Automotive. You can reach them online at pawlikautomotive.com. Or you can call to book in Vancouver (604) 327-7112. You have to book ahead. They're always busy. Pawlik Automotive in Vancouver, BC, Canada. Thanks so much for watching, listening. Thanks Bernie. 

Bernie: Thank you, Mark. Thanks for watching.

About the author 

Bernie Pawlik

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