# Cleaning air conditioning ducts on a car?



## clovis (May 13, 2002)

I have a '98 Monte Carlo that I let sit for a year, outside. I know you shouldn't let it sit, so I started it and drove it a once a month or so. 

I got it back on the road last week, and she still looks and runs great.

A good bit of dirt and soft maple seeds built up under the windshield wiper area while it sat. I cleaned that out, as best I could, but it could use a little more cleaning.

Here is my problem, and my questions:

When I first turn the air conditioning on, there is a fairly strong mildew/dirty smell. It only lasts for 30 seconds at most, and it is nothing horrible. The smell basically goes away altogether, but there might be a very small hint of it in the air. My DW says I have the most sensitive smelling ability this side of the Mississippi...and aside from the first blast of smelly air, it really is nothing.

Where does the air conditioning system on a 98 Monte Carlo draw outside air?

Does it draw air from the vents/mesh right under the wipers, just under the hood, next to the firewall? Is this where most vehicles draw outside air?

How can I clean this? I'm suspecting that mildew or dirt as built up in the ducts under the mesh/ vents.

Can I pour bleach in those vents to kill the smell? 

While I'm asking 10 million dumb questions....how does water escape from those vents, and not get into the car? 

Thank you!!!!!!!


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## Beeman (Dec 29, 2002)

I can give you general info as I'm not very familiar with a 98 Monte. Outside air is drawn from the cowl area. Look at the screened are at the base of the windshield. Condensation from the AC will have a drain at the bottom of the firewall, usually has a rubber piece that allows moisture out but keeps dirt and insects from entering. Usually have to go under car to see it. 
Mildew smell is common on all auto AC systems. AC should be turned off before shutting car and fan run on high to blow moisture off of evap preventing mildew and odor. Since none of us do this smell is very common. Auto parts stores and I'm sure Wal-Mart have different sprays and solutions to mist into the air intake to possibly help. Diluted bleach water misted in might help but them you get the bleach smell.


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## clovis (May 13, 2002)

Thank you so much Beeman!!!!!

I'm wondering if dirt hasn't built up where the rubber piece/drain is, and hasn't allowed water to drain out. I've parked this car in the drive, under a tree, as long as I've owned it.

In instead of spending $6.99 for "AC mildew killer~miracle in a bottle", I am going to consider using diluted bleach, but only after I try to spray water from the hose down into the cowl vents....just to make sure that dirt isn't clogging up the drain.

Again, thank you!!!!!!!!


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## John Carter (Oct 6, 2004)

spray some vinegar down the ducts, It will freshen it right up and kill quiet a bit of the smell


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## clovis (May 13, 2002)

53convert said:


> spray some vinegar down the ducts, It will freshen it right up and kill quiet a bit of the smell


Should I put the vinegar in a spray bottle?

Should I turn the AC on when I do this?

Thanks!!!!!!


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## mightybooboo (Feb 10, 2004)

You can spray Lysol too what some auto manufacturers use in a very expensive can,,helps but wont cure it forever.Yes,run fan and spray into air intake.Some cars also have filters,if so remove it if you can.

The problem,as I understand it,is only a couple manufacturers in that era made ALL models of car air conditioning/My Jetta,2001,same problem,HORRIBLE,when AC died I left it dead.

Now my 1997 Dodge truck,great AC,no issue.

Its possible you have one of the stinky vehicles and basically not much you can really do about it.


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## clovis (May 13, 2002)

mightybooboo said:


> Its possible you have one of the stinky vehicles and basically not much you can really do about it.


If it is, it is entirely my fault. I've been parking it under a tree since I've owned it. Then, when my health took a serious nosedive, I neglected the car.

Even though it is a 12 year old car, it still looks really nice! I even got two compliments today at church! It really does look nice!!!!


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## Bearfootfarm (Jul 13, 2006)

> Does it draw air from the vents/mesh right under the wipers, just under the hood, next to the firewall?


That sounds right. There is a filter there called a "Cabin Air filter" that you can replace that will probably help with the odor too


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## clovis (May 13, 2002)

Bearfootfarm said:


> That sounds right. There is a filter there called a "Cabin Air filter" that you can replace that will probably help with the odor too


Do all cars have these filters...even my 98 Chevy?

I remember Ford introducing a HEPA filter for cabin air sometime ago, but I didn't know GM had them too, at least in 98.


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## mightybooboo (Feb 10, 2004)

Its not your fault.There is a design error in many of em that doesnt allow the moisture out and mold results.

There was a big stink (yup,thats a pun) about em with VW,they essentially did nothing but spray em until you were out of warranty.VW wasnt alone I came to find out.


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## John Carter (Oct 6, 2004)

clovis said:


> Should I put the vinegar in a spray bottle?
> 
> Should I turn the AC on when I do this?
> 
> Thanks!!!!!!


yes and yes.............works great.

The clorox could blow out on your upholstery.


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## Beeman (Dec 29, 2002)

You can have a drain that works great but you'll still get mildew just from the condensation on the metal evaporator core in the HVAC box. Read the owners manual, many tell you how to shut down the AC.
Running a hose at the cowl will not test the drain, and it's a good thing it doesn't or you'd fill your interior with water if the drain was clogged. The water shouldn't be able to get into the HVAC box. If you're checking or clearing the drain be very careful. Inside above the drain is the AC evaporator core. You can poke a hole in it if you go poking around the drain. If the AC drain isn't working the condensation will build up and start overflowing onto the carpet. Run your car on a humid day and you can see the condensation dripping on the ground from the rt. side of the car. That will show you where the drain is.


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## Bearfootfarm (Jul 13, 2006)

> Do all cars have these filters...even my 98 Chevy?


It seems they do. Any good auto parts store can verify it for you

http://www.google.com/imgres?imgurl...in+air+filter&hl=en&safe=off&gbv=2&tbs=isch:1


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## tamsam (May 12, 2006)

Beeman is right. After running the air look for it dripping on the right side under the car. If you see no water you will have to jack it up or get it up someway to get under it to find the drain. If I remember right it should be a rubber hose sticking out near where the firewall makes it's turn to go under the car. The hose should be about an inch across and the end should be flat to keep anything from getting back into it. Good luck getting it fixed. Sam


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## Harry Chickpea (Dec 19, 2008)

Bleach and vinegar are both very corrosive. If you must spray, use something like lysol.


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## Wis Bang 2 (Jan 12, 2010)

clovis said:


> Do all cars have these filters...even my 98 Chevy?
> 
> I remember Ford introducing a HEPA filter for cabin air sometime ago, but I didn't know GM had them too, at least in 98.


My 99 Grand Am had one, '98 Monte is the two door version of the Impala, same as the Grand Prix & Buick Century while the Grand Am was the same as the Malibu. It should have a filter. 

Check your owners manual, it will tell you -or- go ask at Advanced Auto Parts, they will look it up in the computer...


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## clovis (May 13, 2002)

Wis Bang 2 said:


> My 99 Grand Am had one, '98 Monte is the two door version of the Impala, same as the Grand Prix & Buick Century while the Grand Am was the same as the Malibu. It should have a filter.
> 
> Check your owners manual, it will tell you -or- go ask at Advanced Auto Parts, they will look it up in the computer...


I'll try my local mom and pop auto parts retailer. They are much, much cheaper than Advanced, O'Reilly, and AutoZone.


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## clovis (May 13, 2002)

It was very humid here today, and I noticed a big puddle of water under the car today after driving it, and then parking it.

This tells me that the drain is clear.

FWIW, the smell is fading, and can barely be noticed. I think it is just taking a while to air the car out after it has sat for a long, long time.

Thanks so much!!!!!


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## Beeman (Dec 29, 2002)

One of the big problems is the dampness in the AC box attracts and hold pollen and other particles and they cling to the evapoorator. The more you use it and the less you park it under the tree possibly the better it will get.


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## clovis (May 13, 2002)

I think you are right, Beeman.

I drove the car today, several times, and didn't even notice the smell.

I might not do anything with bleach, vinegar, or Lysol.

I sure have learned a BUNCH on this thread!!!!!!

Thank you all for helping and teaching me!!!!!!


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## clovis (May 13, 2002)

Update:

The smell is completely gone. I've done nothing to the car as far as cleaning the ducts.

It has been hot here, and very dry. 

I'll be interested to see if any of the smell returns when rainy season gets here, especially late in the fall.


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