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Phew…hey your air conditioner sure stinks! I could be wrong but I don’t remember cars of the 70’s
and 80’s blowing out smelly air-conditioned air. It was in
the early 90’s when I first heard my niece complain that her
new Plymouth minivan had developed a rude behavior whenever she
turned on the air. Now it seems to be a fairly common complaint.
So much so that several vendors have jumped in with a variety of
products that allow the technician to alleviate the problem. Which leads me to one of the mysteries about this condition: why
do auto dealers seem to be getting the resulting service business,
and not the independents? (If you don’t believe that, ask the
vendors who most is buying their product.) Certainly an answer is
that most of the vehicles that suffer from stinky air are still
under warranty at the time, a dealer gimme. Still though, this is
an ongoing problem. Could it be that independent service shops feel
guilty about this service, like maybe they’re peddling snake
oil? Hopefully we can rearrange some of those ideas. “Houston, we HAVE a problem”
(I couldn’t resist)
Condensation forms on cool evaporator fins and tubes and collects
in the pan. Inlet air brings along contaminants like dirt, pollen
and plant and animal debris, some of which is deposited on the wet
fins and in the pan. Additionally, if a system spends much time
in re-circ mode, it also gathers matter like pet hair and nicotine
and tars from cigarette smoke. Another cause could be leaking evaporators
allowing oil to coat the fins. Certain evaporators, housings and
pans are more prone to accumulating these contaminants than others. Armed with the nourishment (contaminants) listed above, the warm,
moist, dark, environs of the housing encourage beasties (microorganisms,
mold, mildew, fungi, bacteria, etc.) to form and multiply. Being
alive and growing means they produce gas. This gas, a volatile organic
compound, IS the problem: its moldy odor stinks. Car manufacturers turned to professionals, so did I
The auto manufacturers turned to vendors to solve their odor problems.
I asked these companies several questions to assist in preparing
this article. Several of them graciously responded. AirSept, Inc. provided a more scientific description to what I
called beasties. They report that independent laboratories have
identified Aspergillus, Cladesporium, Penicillium along with others
as the fungi growing on coils and other parts of the system. Problem vehicles
I asked the vendors which vehicles seem to be most affected. Four
Seasons reported that while all vehicles are affected to some extent,
their Tech Line receives the greatest number of complaints for the
front wheel drive Daimler-Chrysler/Dodge family of mini-vans. The
evaporator odor problem could be found in Mitchell-On-Demand Technical
Service Bulletins for 1993 model year vehicles covering Ford (Bulletin
# 98-2-7), General Motors (99-01-39-004, & 53-12-12A), and Daimler-Chrysler/Dodge
(24-11-97). AirSept believes that “limited under hood space in downsized
vehicles, along with increased need for air cooling in vehicles
with higher glass content, led vehicle manufacturers to reduce the
size of a/c evaporators while simultaneously increasing the fin
count. These more densely packed evaporators trap and hold more
moisture.” Cliplight Manufacturing Company has no evidence that R-134a evaporators
are any worse to foul than those using R-12. They point out that
in fact, an R-12 vehicle will be at least eight years older and
therefore likely to be packed with eight more years worth of contaminants. The cure(s)
While many products include a deodorizer as part of their package,
for obvious reasons we did not invite pure deodorizer vendors to
this party. Legitimate cures for evap-stink are: 1. Apply a microbial
and moisture-resistant coating to the coil to reduce the problem
in the first place, 2. Clean the evaporator (and pan, housing, air
inlet, etc.) and 3. Using an electronic timer to cycle the blower
at certain intervals after the vehicle has been shut down. The latter
action dehydrates the evaporator in less-than-humid areas, which
stifles microbial formation. Many manufacturers now install evaporators that have been coated
with both antimicrobial and hydrophilic (i.e. water shedding—thanks
again AirSept) materials. However, those coatings are not permanent.
Once depleted, the evaporator can then become a microbial breeding
ground.
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