The fresh air intake comes through the grates that are in front of the
windshield below the wipers.
I have a 1997 Explorer that developed a moldy smell when the defrosters or
AC was turned on too but went away after about a minute or two of running
the blower. It tried the sprays and the deodorizers and they worked for a
while but the smell kept coming back so I decided that I had to get to the
root of the problem.
I originally thought that the drain line from the enclosure that surrounds
the AC/defroster condenser coil was clogged resulting in standing water and
causing the foul smell. I ran the AC and watched to see if there was
condenser water dripping out from below the vehicle. I did see some water
dripping out, which also helped me locate the drain line, and figured that
maybe it was only partially clogged. So I pushed a stiff wire into the
drain hose to see if there might be a partial obstruction. A little debris
came out so I assumed that I had fixed the problem, but the problem returned
again even though I was getting adequate drainage.
I then concluded that a more thorough cleaning would be needed to get rid of
this smell. The easiest way that I could see to gain access to the AC
condenser coil without a major disassembly of the vehicle was to remove the
blower motor assembly. On a '97 it's pretty accessible being under the hood
on the passenger side right up against the firewall. I had to remove a
couple of screws from the washer fluid and coolant reservoirs and move them
forward slightly to get the blower motor with it's attached flange out.
Once that was out I could see the condenser pretty well. I found that my
problem was caused by debris (leaf particles and other small organic
particulate) that had accumulated at the bottom of the enclosure that houses
the condenser coil. Since this junk was damp, mold had begun to grow and
cause the odor.
Unfortunately, the parking lot where I work has a row of large shrubbery
right in front of the vehicles. Every time the wind blows, debris from
these shrubs gets blown onto the cars. While most of it is large enough to
be blocked by the grating, some of the smaller particles managed to get
through. After a few years of this, enough junk got down into the condenser
coil area and started to decay causing the odor. The problem seemed to be
worse in the summer especially since my truck is kept in the garage. The
combination of dead leaves and debris, condenser water and heat made things
I was able to clean out the debris by sticking a garden hose into the blower
motor opening and flushing all the gunk out. If you try this make sure you
get both sides of the condenser coil. I was able to get the spray from the
hose to the backside of the condenser and wash it out too. I then let the
water drain out from the area and sprayed it with a water/bleach solution to
kill all the mold. I haven't had the odor since although I suspect that
another cleaning in the future will be necessary as the same thing will
probably occur after a few more years of accumulating junk from the shrubs.
Good luck and I hope this gives you a little insight to solving your
(Remove the nospam_) to reply.
Seems like there is a "perpetual" TSB for this. If it's the one I'm
thinking about, it seems to get issued for just about every year, and
consists of some type of chemical/spray that is introduced into the
evaporator compartment of the AC system. Seems like it was more than just a
deodorizer - I seem to remember the TSB mentioning some type of
"encapsulation" spray with a specific methodology for application. I had
the dealer do this to mine while it was still under warranty, and it really
did help for about two years, after which the smell came back. Sounds like
Don R. diagnosed the real root of the problem. I don't seem to have as much
trouble if I spend most of the summer using Max A/C... my guess is that
maybe this keeps recirculation damper open even while parked, giving the
evaporator compartment a better chance to dry out...
The problem I have is not a moldy smell, rather a smoky smell.
Sometimes so intense I have to crack a window to get some fresh air so
my eyes stop burning! The reason is that in my '94 the leaves and crap
get into the plenum and pack up against the power resistors for the
heater blower motor. Whichever resistor is selected for a given blower
speed will get hot -- some of them VERY hot -- while the blower is on.
I've found that running the fan on high is least likely to make the
burning smell (aside from "off" :-), whether because that position uses
no resistor, that resistor doesn't get as hot, or that resistor is
located so that crap doesn't pack up against it.
A couple of times I've taken apart the blower assembly and pulled out
the junk, but it's a real PITA to get at.
Gordon S. Hlavenka http://www.crashelectronics.com
"If we imagined he could _find_ the car,
My '94 EB had the leaf problem so bad that one night they caught fire. You
haven't lived until you're driving down a foggy road at midnight, turn on
the fan and start seeing smoke billowing out of the vents. I kept thinking
that there "must be a forrest fire around here somewhere". I luckily turned
off the fan so that I wouldn't "fan" the flames but it smoldered for quite a
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