Re: A/C odor
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Posted by willard on August 29, 03 at 17:07:27:
In Reply to: A/C odor posted by Mark on August 13, 03 at 18:29:09:
: Every time we start the car when the a/c has been left on, we get a
very sour odor.
Most describe it as "dirty gym socks".
The below was originally posted to a ford who was having windsield
fogging problems, but your odor is the result of the exact same
circumstance, microbes breeding by the billions within the damp, dank,
darkness of the A/C evaporator and it's enclosure.
What you smell is their "out-gassing" and the odor from their
"leavings", body waste.
Lovely, Huh?
The problem you describe has always existed since the advent of A/C in
automobiles, but became much more of a nuisence with the advent of
non-freon refrigerants that have a much lower cooling efficiency than
freon.
To make up for the loss in efficiency the A/C evaporator had to be
redesigned. As a result modern day A/C evaporators can act very much
like a sponge. In order to increase efficiency the evaporator had to
become much more complex, more metal vanes, cooling surfaces exposed
to the airflow, all stacked into a very tight space under your dash.
In simple terms, a SPONGE.
When you park your car for the evening after a humid day of heavy A/C
use, the evaporator will likely be saturated, throughly CHOKED, with
moisture. During the day as the system continued to operate the
condensed mositure would accumulate into droplets large enough for
gravity to overcome viscosity and then run out the drain tube provided
for tha very purpose.
But not your car is sitting there with a very thin firm of moisture
covering about 10,000 square inches (92 Lexus LS400) of cooling vane
surface.
If you park inside it will help tremendously if you can lower all of
the windows during the night. Then, unless the garage is quite cool,
the thin film will evaporate into the local atmosphere and much of it
will then end up outside the vehicle.
Another aspect of this that you might take serious note of is the fact
that during the winter when outside temperatures decline below
freezing the vehicle's A/C cooling capability will become totally and
completely inoperable. Many modern day systems actually disable the
A/C compressor altogether when the outside temperature declines to 35F
and below.
It's cold outside, so who cares, you say.
Well, you do care.
Many, if not most, modern day automatic A/C systems will operate the
A/C system all year around in order to more closely regulate the cabin
temperature and humidity.
But even if that is not the case almost ALL systems will automatically
activate the A/C when the defrost/defog/demist mode is activated.
So there are two things to remember.
First, if you happen to use the A/C for defogging during fairly cool
weather then when you exit that mode the thin film of moisture left
will oftentimes act like a MOISTURE BOMB. Shortly after you deactivate
defog mode that thin film of mositure will begin to evaporate back
into the incoming airstream in which case you might end up with higher
cabin humidity, and possibly a more severely fogged windshield, than
before the first use of the defog function.
Second, and this is for those of you with automatic A/C systems or
climate control, as you drive your vehicle into an area of declining
temperatures the A/C control system may, spontaneously and without any
indication to you whatsoever, disable the A/C compressor completely
due to outside temperatures reaching 35F or below.
Imagine driving along on a cold but bright winter's day, four people
in the car warm and cozy. Now as you approach the higher mountain
elevations the A/C compressor shuts down due to the declining
temperature. At 65 MPH the windshield interior surface is becoming
thoroughly chilled due to the impinging COLD airflow.
AND now that thin film of moisture is evaporating into the incoming
airstream and being combined within the cabin atmosphere with the
moist byproducts of human metabolism.
Very soon you will begin to small wisps of condensation at the lower
corners of the windshield due to rising cabin humdity and a chilled
windshield surface. Remember, now, the A/C is disabled
and cannot be used to dehumidify the incoming airstream. And even if
it could be activated it's usefullness at dehumidifying an already
cold incoming airstream is negligible at best.
But go ahead, activate the defrost/defog/demist function.
The result will very likely be exactly what I encountered in the
winter of 92/93 in my brand new Lexus LS400.
A quite thoroughly and completely fogged over windshield.
When you activated the defrost/defog/demist function the result was
that now ALL of the humid system airflow is routed toward the cold
windshield surface.
What you REALLY need to do FIRST, is WARM that chilled windshield
surface to raise it's dewpoint and begin to evaporate the already
condensed moisture.
You can do that best by turning the heat demand of the system to MAX
(the blower speed will usually increase automatically as you do this,
if not...), and now once the heat is really flowing and the blower is
at full speed then activate the defrost/defog/demist mode.
There is an aftermarket product available that about an hour after the
vehicle is shut down will begin to run the system blower
intermittently to disperse the moisture outside of the A/C plenum as
it begins to evaporate from the evaporator vanes.
I understand that Ford is aware of your problem and will oftentimes
recommend that the dealer install this device if the customer
complains.
See:
http://www.airsept.com/eed.html
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Comments:
: : Every time we start the car when the a/c has been left on, we get
a very sour odor.
: Most describe it as "dirty gym socks".
: The below was originally posted to a ford who was having windsield
fogging problems, but your odor is the result of the exact same
circumstance, microbes breeding by the billions within the damp, dank,
darkness of the A/C evaporator and it's enclosure.
: What you smell is their "out-gassing" and the odor from their
"leavings", body waste.
: Lovely, Huh?
: The problem you describe has always existed since the advent of A/C
in automobiles, but became much more of a nuisence with the advent of
non-freon refrigerants that have a much lower cooling efficiency than
freon.
:
: To make up for the loss in efficiency the A/C evaporator had to be
redesigned. As a result modern day A/C evaporators can act very much
like a sponge. In order to increase efficiency the evaporator had to
become much more complex, more metal vanes, cooling surfaces exposed
to the airflow, all stacked into a very tight space under your dash.
:
: In simple terms, a SPONGE.
:
: When you park your car for the evening after a humid day of heavy
A/C use, the evaporator will likely be saturated, throughly CHOKED,
with moisture. During the day as the system continued to operate the
condensed mositure would accumulate into droplets large enough for
gravity to overcome viscosity and then run out the drain tube provided
for tha very purpose.
:
: But not your car is sitting there with a very thin firm of moisture
covering about 10,000 square inches (92 Lexus LS400) of cooling vane
surface.
:
: If you park inside it will help tremendously if you can lower all of
the windows during the night. Then, unless the garage is quite cool,
the thin film will evaporate into the local atmosphere and much of it
will then end up outside the vehicle.
:
: Another aspect of this that you might take serious note of is the
fact that during the winter when outside temperatures decline below
freezing the vehicle's A/C cooling capability will become totally and
completely inoperable. Many modern day systems actually disable the
A/C compressor altogether when the outside temperature declines to 35F
and below.
:
: It's cold outside, so who cares, you say.
:
: Well, you do care.
:
: Many, if not most, modern day automatic A/C systems will operate the
A/C system all year around in order to more closely regulate the cabin
temperature and humidity.
:
: But even if that is not the case almost ALL systems will
automatically activate the A/C when the defrost/defog/demist mode is
activated.
:
: So there are two things to remember.
:
: First, if you happen to use the A/C for defogging during fairly cool
weather then when you exit that mode the thin film of moisture left
will oftentimes act like a MOISTURE BOMB. Shortly after you deactivate
defog mode that thin film of mositure will begin to evaporate back
into the incoming airstream in which case you might end up with higher
cabin humidity, and possibly a more severely fogged windshield, than
before the first use of the defog function.
:
: Second, and this is for those of you with automatic A/C systems or
climate control, as you drive your vehicle into an area of declining
temperatures the A/C control system may, spontaneously and without any
indication to you whatsoever, disable the A/C compressor completely
due to outside temperatures reaching 35F or below.
:
: Imagine driving along on a cold but bright winter's day, four people
in the car warm and cozy. Now as you approach the higher mountain
elevations the A/C compressor shuts down due to the declining
temperature. At 65 MPH the windshield interior surface is becoming
thoroughly chilled due to the impinging COLD airflow.
:
: AND now that thin film of moisture is evaporating into the incoming
airstream and being combined within the cabin atmosphere with the
moist byproducts of human metabolism.
:
: Very soon you will begin to small wisps of condensation at the lower
corners of the windshield due to rising cabin humdity and a chilled
windshield surface. Remember, now, the A/C is disabled
: and cannot be used to dehumidify the incoming airstream. And even if
it could be activated it's usefullness at dehumidifying an already
cold incoming airstream is negligible at best.
:
: But go ahead, activate the defrost/defog/demist function.
:
: The result will very likely be exactly what I encountered in the
winter of 92/93 in my brand new Lexus LS400.
:
: A quite thoroughly and completely fogged over windshield.
:
: When you activated the defrost/defog/demist function the result was
that now ALL of the humid system airflow is routed toward the cold
windshield surface.
:
: What you REALLY need to do FIRST, is WARM that chilled windshield
surface to raise it's dewpoint and begin to evaporate the already
condensed moisture.
:
: You can do that best by turning the heat demand of the system to MAX
(the blower speed will usually increase automatically as you do this,
if not...), and now once the heat is really flowing and the blower is
at full speed then activate the defrost/defog/demist mode.
:
: There is an aftermarket product available that about an hour after
the vehicle is shut down will begin to run the system blower
intermittently to disperse the moisture outside of the A/C plenum as
it begins to evaporate from the evaporator vanes.
:
: I understand that Ford is aware of your problem and will oftentimes
recommend that the dealer install this device if the customer
complains.
: See:
: http://www.airsept.com/eed.html
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