Stinky Van

I have an almost 11 year old van. Great condition, 40,000 miles. The only problem is that the vents were blowing out an odor. A friend said it was a build up of mildew and bacteria and that “Mildew Buster” would clear up the problem. He sprayed it on twice (in “the box”) and by the next day it started smelling again. Does that mean there is still mildew blowing out? Can this be fixed with the “Mildew Blaster”? Is it healthy for me and my kids to breathe this stuff?

Help! I need some ideas!

You need to remove the (outside) fresh air vent cover that is located immediately below the windshield.

Vacuum out all the debris (old leaves, etc) and change the cabin air filter (if equipped). Check your owners manual (or phone a dealer) for location.
Perhaps squirt a mix of water and vinegar into the opening and turn the heater fan on full.

Is it healthy to breathe mold and mildew? I think you know the answer already.

There are three common problems.

First is an accumulation of leaves etc in the air intake in front of the windscreen.  Make sure it is clean and it drains well.  

Second is a build up of mold on the A/C area.  That again can be a drain issue.  In most cars it drains on the passenger side of the car right in front of where the passenger would have their feet.  Look under the car for a small black rubber tube. Try using some string trimmer string to clear it out.  

After either of the above you may need to spray some Lysol (or if you like the fancy more expensive stuff form the auto parts store) into the air intake.  

Third is a dead animal or animal leavings (nest materials etc. This is more likely if you park your car outside. You have to clean the stuff out and try to block the path they may have used.

Good Luck

Thanks for the suggestions. My friend said he’d spray it again but may have to take out the “box” (I don’t know what that is) but he said that would be a major undertaking. I’ll gently suggest your ideas. Thanks!

You are not alone. A lot of people complain about this. I am very susceptible to mold allergies so I have done some research. I think you are on the right track by looking to clean. Most people are looking for a magic spray that will fix the problem and lots of people suggest this approach – Lysol or similar stuff sprayed into the AC system with the blower running and the windows open. This may work for a time, but it is probably only a temporary solution. It will kill existing bacteria and fungi, but they will start to regrow as soon as the culture medium (crap) in your AC system is reinnoculated (immediately).

First the simple solutions. Check to be sure that your AC drain is not clogged. Try not to park under trees and keep the air intake grill/screen free of debris. Another simple thing to do is when you park the car be sure to leave your HVAC system in any position BUT “off”, “max” or “recirc”. Some owners’ manuals specify this to let air circulate through the system. Try turning the temp control to full hot after parking before you shut the car off. This, in theory might circulate hot dry air from the cabin back through the evap coil by convection. Note well the “in theory”. I have not tested this theory, but it seemed to help me a little. If you live where it is not too uncomfortable, turn the AC off some time before you park, it might help dry the system out. Note that running it right before parking with the heat on is not likely to help since the heater is AFTER the AC coil in any car I have looked at.

You need to clean out your system and keep it from getting full of leaves again. Some models are easier than others to get to. Often the blower motor can be pulled out or the blower motor resistor assembly can be removed from the plenum to gain access to the AC evaporator coil. With some cars these elements are easy to get to but others are very difficult. If you can get at the coil you can spray some detergent in there. I have also used 10% bleach after the detergents. If you use the latter I would not let it sit for more than a few minutes before rinsing extensively because you could corrode aluminum parts.

There are lots of cleaners and coatings for auto and home AC systems. Some Foaming or other cleaners rumored to be available for residential use should work. AirSept makes some coatings for Auto use. They require removal of the coil which will cost you time or money. I have not tried them.

Some car models seem prone to this problem. It must have something to do with how well the systems dry out after shut-off and how much crud collects in the “coil” (Now, I believe, many manufacturers use flat-plate heat exchangers.) I hope that the answer to the problem will be effective filters to keep the food away from the microbes that like to grow in moist, dark places.

I have spent a lot of time on this problem and I’ve had some generous help from people on web fora. Getting information about the auto manufacturers’ equipment was not easy. It seems that not many people out in the trenches (auto techs), even the factory-trained ones, know about them.

Despite the attempts at secrecy, I have found out how some of the manufacturers remedies work. Ford has or had a kit and a TSB (02-11-7 ,JUN 02, A/C System - Musty/Mildew Odors) . There is an “afterblow” or “purge” module and two wire kits to make it fit their various models. The price would be about $200 total depending on what wiring harness is needed. It runs the blower on high for a couple of minutes some time after the AC and car are shut off. The delay is important because no cold surface is going to dry with hot, moist air blowing over it. It also prevents operation at convenience store stops. I have also read recently that Ford no longer offers this stuff because of run-down battery problems. I don’t recall where I read this and I have not checked the facts.

Saturn has a kit for about $125 (delayed blower motor controller: 21031158). It seemed to be adaptable to any car. I was told that it runs the blower for 5 minutes after the car is turned off for 50 minutes to allow the coil to warm up.

Airsept probably still has a web site. They also make an afterblow module that is universal. The cost was about $300 to AC techs, I believe. It is costly, but it should work better than the others. Look a the site for the features. It starts a pulse cycle after giving some time for evap to warm. The pulse operation is supposed to squeeze the most out of your battery’s electrons by allowing the evap box warm up a little between the drying (cooling) pulses. It also has battery protection. It sounds good to me.

Airsept also makes cleaners and coatings to prevent microbe growth. These should also work. For most, however, you need to take the system apart to coat them. Note that there are foaming cleaners available for home HVAC. They should also work. Note that DSS (Dirty Socks Syndrome) is an issue with home units as well.

I live in a very hot/humid place. I pulled the blower motor from my car, cleaned and disinfected the evap. Fortunately one side is is readily accessible in my car. The evap looked sparkling clean, before I started so the microbe growth might be somewhere else in the plenum. I decided that I could make my own afterblow module with a little time and a soldering iron. I saved a lot of money and got great performance.

I went through several designs and decided that, in my climate, on most days when the humidity is high, I would need an auxiliary battery to dry the evaporator out with the HVAC blower in combination with systems like the commercial ones. I decided to reverse the afterblow. This blows cool, dry cabin air past the heater core and the evap. I made it with a small, plastic squirrel-cage blower, an inexpensive “multimode” timer kit and a couple of automotive relays. I plumbed the blower in to the passenger foot well heater outlet (not as easy as it sounds). I have a seasonal change-over of removing this and taking the duct tape off the other 3 heater outlets.

During AC season (10-12 month) I have to remember to put the system in the “floor” mode and turn the heater to high as I park. I have the timer triggered on the AC control so it activates if the AC has been on and runs the little blower for 2 h. I have a reset button and an on/off switch stuck behind the lighter in the ashtray. All the equipment is tucked up behind the dash. I have also added a little $20 pneumatic valve that opens the dash vent ducts when the blower stops to allow better circulation in case there is any residual moisture in there.

My solution is obviously not a universal solution, but it works for me and was inexpensive. My total costs were higher because I had a lot of false starts, but to repeat it would probably only cost about $30 excluding the valve. I did spend a lot of time on it.

The “Multimode Timer” kit is available at several mail/wwweb places. A couple:


Manual at:

Thanks so much for taking the time to type a very informative reply. I think I’ll just print it and give it to my friend who is looking at my van since he’ll probably understand more what your talking about. Since he already sprayed it and the smell came back he’s thinking it may not be the mildew. Sounds like though a spill would have burned off by now. It seems directly related to the AC since the AC has gone out twice since we got it and the smell has worsened each time its fixed. The smell is distinct to me - the only way I can explain it is that it smells like cattle. Not a pleasant smell to have blowing in your van! The smell kinda wears off after you get driving but it is always there when the van is first turned on and you begin driving.