Moldy Smell From AC AFTER Running It

1985taylor1925

1985taylor1925

Senior Member
Alright, I need to explain the details of my moldy smell, and ask a few questions. I know its long, but please read through my post, before offering random advice. People love to offer some advice which, if they had just read through my post they would have found I already tried it.

This is a big concern for me because I have a genetic issue in which my immune system lacks the ability to clear mold spores and toxins from my body. This is VERY different then a mold allergy, which is extremely common, and not serious at all. For me, mold will literally make me sick with flu symptoms, neurological symptoms, neuropathy, dizziness, brain fog, severe fatigue, and many other symptoms that are quite severe.

Here's the situation:

It just recently got warm enough to use the AC, so I ran it for about 20 minutes driving to work this past week. I ran it with the vents turned to fresh air, not recirculate, and there was NO mold smell initially. Then after work when I started the truck and turned ONLY the fresh air vent on (no AC) to get some air flow, I got the musky moldy smell coming from the vents. I then got the same thing the next day. So I then turned the system to recirculate and the moldy smell went away for the most part after a bit.

I was looking for a diagram of the entire system as I don't understand how it all works, but really couldn't find much. I know the AC evaporator is burried deep under the dash. But I don't know where the mold grows? Ive read that mold spores, dust, pollen, leaves, etc can get to the evaporator. But does that mean they get inside the system, or just collect on the outside of the evaporator?

This will be the first suggestion someone will give, so I'll tell you that I have already ran an entire can of aerosol cleaner through the system. I dont remember the brand now, but I know it was one of the popular ones that shops use to clean out the system. It was highly reviewed so I tried it and it did seem to eliminate any moldy smell. This was last summer. The thing is, I live in Cheyenne, WY, which is an EXTREMELY dry climate. No humidity, very little precipitation, and I used the AC maybe a total of 5 times last summer. So I dont understand how I could have any mold issues whatsoever?

I already know to help prevent this youre supposed to turn off the AC and turn on the fan about 5 minutes before turning off the car to dry things out. Again, I barely used the AC last year. So, does anyone have any advice here? Is my only option to take everything apart and replace the evaporator and clean everything? For me, this is a big issue and it seems like its going to be an ongoing issue since I just cleaned the system less than a year ago, and even with the dry climate I already have the moldy smell back. I am wondering if my best option is to sell the truck, which would be financially difficult right now.

Any advice would be appreciated, especially if someone could explain how the system works and specifically where the mold might grow? Thanks
 
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There's a specific product that you inject into the heater housing to clean the mold and mildew out of the evaporator. You can google for it.
 
A couple or three thoughts:
1. Make your next car one with a cabin air filter.
2. Since you got smell in fresh, but not recirculate(the opposite of the usual 'dank smell from the A/C on recirc issue), look into cleaning the fresh air intake path. There are standard automotive sprays you can use, but look into some medical-grade Lysol or other serious disinfectant/mold killer. Johnson wax used to make a very strong product called 'EndBac", but it was apparently declared too dangerous and the formula was changed. Maybe it is still good?
NOTE: Many disinfectants have alcohol in them and may be flammable. Do not use...or be extremely careful about using... flammable chemicals if the chemicals are going to pass by an running electric motor or energized switches/circuits. If you use something flammable, flush it out with compressed air or inert gas before operating/energizing the equipment.
3. One pass with any cleaner is commonly not enough. You may have to treat it several times.
I had the standard "gunk in the evaporator" smell when on recirc.
I sprayed my evaporator once with the standard foaming product(Toyota brand).
Then a couple months later, a second treatment with half a can of CRC Lectro-Motive (NON-Flammable) solvent sprayed directly on the evaporator(through the blower hole)followed by another spray treatment using FJC #5914 Foaming A/C cleaner.
And...guess what...It's still going to need another treatment...there's still a small amount of dank smell on lo fan + recirc. Lucky I bought 2 cans of the FJC stuff.
Good luck, and don't jeopardize your health just to drive a "cool car".
 
I had the same problem with my 01. I used the Toyota AC Refresh Kit, it was about $30 at the stealership. I know you mentioned a spray you used for the system but the root of the problem is the evap coils and the housing it is encased in. This kit is a foam kit that cleans out the evap coils and the housing. The kit also comes with a spray for the vents but I feel it wasn't as important as the foam since the root of the problem was the coils. Check out this video on how it works. It solved my problem.
 
With not much rain in your area really the only thing that would do what your talking about is the evap core. AC systems don't cool air, they remove moister from the air and that is what lowers the air temps. If the moister is not draining then you get the problem you are describing. I have used the kool-it foam many times and I like it better than most. How I do it.
First make sure the evap drain is not clogged up
2. Run the heat for 10-15 mins, shut the truck off
3. Stick the tube up through the evap drain.
4. Hold a rag over where the tube goes into the drain so it wont come back out 5. Spray the whole can till empty. If it comes out the vent its not going to hurt anything.
6. Let it sit 10-15 mins
7. Turn heat back on and let it run for 30 mins
It also help clear it out if the truck is pointed down hill
 
ATX-Runner said:
With not much rain in your area really the only thing that would do what your talking about is the evap core. AC systems don't cool air, they remove moister from the air and that is what lowers the air temps. If the moister is not draining then you get the problem you are describing. I have used the kool-it foam many times and I like it better than most. How I do it.
First make sure the evap drain is not clogged up
2. Run the heat for 10-15 mins, shut the truck off
3. Stick the tube up through the evap drain.
4. Hold a rag over where the tube goes into the drain so it wont come back out 5. Spray the whole can till empty. If it comes out the vent its not going to hurt anything.
6. Let it sit 10-15 mins
7. Turn heat back on and let it run for 30 mins
It also help clear it out if the truck is pointed down hill
Click to expand...

Where is the evaporator drain located exactly?
 
You should have a nice puddle under your truck after running the ac for about 10 minutes. Less if it's a humid day. If not, then your drain is plugged.

Also, need to clarify something someone wrote earlier that ac systems don't cool air but only remove moisture. Not quite right. They lower air temps below the dewpoint which is what separates the moisture from the air. So AC systems cool AND dry the air at the same time.
 
Okay so a few things to keep in mind. As a service writer several years ago this was a complaint every summer from customers for all types of cars. So I know I can help.
-First if you want to clean the evap coil its a major job but you can access and see it by removing the blower resistor on the box. It's behind the glove box. You can't see it all but you be able to see it.
-Second all the ideas to freshen it up are good and work I'm sure. But if there is mold, I can't imagine it would kill it. Gotta have bleach or sporicidin for that.
-Third is good news. There is no mold. When you run the A/C the evap helps "evap" water which drains from your car to the ground. When you shut off your car the water droplets are all over the evap core. So it just sits there in your warming vehicle until it slowly dries. And stagnant water in warm air will get "musty". So when you turn on the fan (with or without the A/C on) the musty smell blows into the cabin!
-Fourth. There is a very simple solution. I have used this method for more than 20 years. When you are driving with the A/C on, turn it off while allowing the fan to blow for the final few minutes of your drive. Needs to be on the fresh air setting (always really). This will quickly dry all the water in the evap coil so it will be dry when you shut off the truck. And no more smell!

Side note. Most cars today with electronic controls for the HVAC automatically divert to the fresh air setting after a set amount of time just for this reason.

Hope this helps.
 
Coward said:
Okay so a few things to keep in mind. As a service writer several years ago this was a complaint every summer from customers for all types of cars. So I know I can help.
-First if you want to clean the evap coil its a major job but you can access and see it by removing the blower resistor on the box. It's behind the glove box. You can't see it all but you be able to see it.
-Second all the ideas to freshen it up are good and work I'm sure. But if there is mold, I can't imagine it would kill it. Gotta have bleach or sporicidin for that.
-Third is good news. There is no mold. When you run the A/C the evap helps "evap" water which drains from your car to the ground. When you shut off your car the water droplets are all over the evap core. So it just sits there in your warming vehicle until it slowly dries. And stagnant water in warm air will get "musty". So when you turn on the fan (with or without the A/C on) the musty smell blows into the cabin!
-Fourth. There is a very simple solution. I have used this method for more than 20 years. When you are driving with the A/C on, turn it off while allowing the fan to blow for the final few minutes of your drive. Needs to be on the fresh air setting (always really). This will quickly dry all the water in the evap coil so it will be dry when you shut off the truck. And no more smell!

Side note. Most cars today with electronic controls for the HVAC automatically divert to the fresh air setting after a set amount of time just for this reason.

Hope this helps.
Click to expand...

Yeah, I know you're supposed to turn it to fresh air with ac off 5 minutes or so before turning off the system. I usually remember. And you are definitely right about killing mold. Mold is a hearty organism and really needs to be soaked in bleach for a while and then physically removed. Otherwise it can lie dormant and come back. I don't trust the spray products to actually kill everything. Though they are better than nothing. I actually work in a lab, partly as a microbiologist. Usually where there's mold there's also bacteria growing with it as a symbiotic organism. The spray cleaners will kill more of the bacteria, but not so much the mold

But how do you know there is no mold? That musky smell is hallmark of mold. I don't know what else could be causing it. What I've read is that dust, mold spores, pollen, bits of leaves, bugs, etc get on the evap core through the vents. And then when there's condensation on the evap from using the ac, mold grows on the evap using those particles for food. Is that true from your experience?

Last, to clean the evap coil you're saying I don't need to remove the entire dash?
 
Well, I assume there is none. If there was mold (like my shower) it would always be there and smell. As opposed to the musty smell in the right circumstances. As far as cleaning goes, if you remove the blower resistor you can see a good portion of the evap coil. If there is some mold you might see it and spray it with bleach or sporicidin or whatever. Or at least confirm you need to remove and disassemble to box. For sure the only way to confirm zero mold is to take everything apart, inspect it, and clean it. And believe me the coils are dirty by now on trucks as old as ours. I understand you have a serious medical concern. From an allergen standpoint my wife's allergic to EVERYTHING and her sneez-o-meter is low inside my truck! Lastly try extended the blower on A/C off technic for longer just ensure the coil is good a dry. Oh and read up on ozone treatments, they use those for water damage in houses to kill mold. Hope this is helpful.
 
1985taylor1925 said:
Yeah, I know you're supposed to turn it to fresh air with ac off 5 minutes or so before turning off the system. I usually remember. And you are definitely right about killing mold. Mold is a hearty organism and really needs to be soaked in bleach for a while and then physically removed. Otherwise it can lie dormant and come back. I don't trust the spray products to actually kill everything. Though they are better than nothing. I actually work in a lab, partly as a microbiologist. Usually where there's mold there's also bacteria growing with it as a symbiotic organism. The spray cleaners will kill more of the bacteria, but not so much the mold

But how do you know there is no mold? That musky smell is hallmark of mold. I don't know what else could be causing it. What I've read is that dust, mold spores, pollen, bits of leaves, bugs, etc get on the evap core through the vents. And then when there's condensation on the evap from using the ac, mold grows on the evap using those particles for food. Is that true from your experience?

Last, to clean the evap coil you're saying I don't need to remove the entire dash?
Click to expand...

Getting to the evap coils would be a PITA because it is encased in a plastic box under your glovebox. You can see it clear as day, as a matter of fact the bottom of the box is where the condensation accumulates and then drains out the other side of the firewall. With the Toyota Foam Cleaner you just spray the foam using the hose with rubber tip it comes with into the drain in the firewall. The foam fills the evap box and saturates the coils inside. After a few minuets, the foam returns to a liquid state and flows out the drain again taking with it all the crud inside of the evap coils. I would definitely do this first before you attempt to remove the evap coils. I'm pretty certain this will solve your problem.
 
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