This
is a fairly common complaint. What causes it?
It is principally
caused by the growth of bacteria on the AC evaporator and in the remains
of any water (condensate) still sitting in the plastic box that surrounds
the evaporator. In a mild case it smells similar to a fridge which is
opened for the first time after several days. In a serious case it can
smell a great deal stronger and was once described to me as being like
'cat's wee'. We all have different abilities in our sense of smell and
what may be a slight annoyance to one person might be almost unbearable
to another.
Firstly let me
reassure you that contrary to what you may have heard elsewhere it is
not possible to contract Legionnaires Disease from the AC in a car. Legionnella
pneumophila are a problem only in the air conditioning systems of large
buildings where they use chilled water to transmit the cooling from one
part of the building to another. No vehicle uses any water to achieve
the cooling.
Nevertheless it
may be possible to contract slight throat infections from a poorly maintained
car AC system. I haven't yet seen any definitive proof that this is possible
but over the years a number of people I have spoken to are convinced that
this has happened to them.
How do these bacteria
appear in sufficient numbers to cause either a smell or a health problem?
If the car's AC is working well then new condensate is appearing on the
evaporator all the time and simply washes any existing bacteria off, collects
in the tray beneath and then drips onto the road through the condensate
pipe. But if the AC is scarcely working, usually due to low refrigerant
charge, this condensate is not being produced and this small amount of
water becomes polluted with bacteria, verdigris and every other nastiness
there may be in the air and with fairly ideal breeding conditions in a
warm damp place turns into a veritable soup which will probably pong to
high heaven. Quite simply recharging the AC and bringing the condensate
supply back to normal may wash this nastiness away and within a day or
so may completely remove the unpleasant smells. Sometimes however perhaps
due to the design of the evaporator the smell lingers a little. Rather
than trying to disguise it with scented products it is better to eliminate
it altogether with a bacterial disinfectant in the form of an aerosol
spray or better still an ultrasonically produced disinfecting mist which
is circulated around the cabin, the vents, the ducting and the evaporator.
How to
rid your car of these bacteria? Often simply recharging the system will
cure the problem. If however the car has been recharged recently and yet
the smell still persists then the problem is likely to be more deep seated
and the system airways may need disinfecting. The cheap and easy method
is to buy a specialist aerosol from a motor factor or accessory shop which
will disinfect and deodorize the evaporator, just follow the instructions
on the can. Perhaps the best method for stubborn cases is the fine mist
deodorizer produced by an ultrasonic piezo device. This bit of kit is
too expensive for the average car owner to consider owning but cleaning
using this or similar equipment is often offered as a service by AC professionals
Contact
me
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