Foggy windshield
07-27-01, 01:49 PM
#1
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Hello,
I thought I would consult your collective wisdom to find an answer to my problem. I own a 2000 RX300.
For the past month, I have noticed this fog on the interior windshield near the vents. This fog progressively gets worse and eventually obstructs my view. I have cleaned and polished the windshield; to find the problem still exists. I assumed there might be a leak in the air conditioner, so I finally brought the car to the dealer; they said they couldn't help me. Has anyone dealt with this problem?
Any help would be appreciated.
I thought I would consult your collective wisdom to find an answer to my problem. I own a 2000 RX300.
For the past month, I have noticed this fog on the interior windshield near the vents. This fog progressively gets worse and eventually obstructs my view. I have cleaned and polished the windshield; to find the problem still exists. I assumed there might be a leak in the air conditioner, so I finally brought the car to the dealer; they said they couldn't help me. Has anyone dealt with this problem?
Any help would be appreciated.
09-28-01, 08:14 PM
#3
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When this happens, turn on the AC button and it will go away fast. Also take the system out of recirculation mode to let in some outside air, and it will help out. The problem is that the RX is too good at keeping out the outside air, and all that water vapor from our breath accumulates.
09-28-01, 09:49 PM
#4
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Put your climate control in auto and hit the front de-frost button. This will turn on the AC (if off) and direct air to the proper vent.
Salim
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09-29-01, 10:39 AM
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"I have noticed this fog on the interior windshield near the vents"
May I take the liberty of restating?
"I have noticed this fog/condensation forming on the interior surface of the windshield near the defrost vents."
?????
Condensation forms on the interior windshield surface because that surface is COLD enough to lower the temperature of the humid atmosphere flowing over it to its dewpoint. As you lower the temperature of a humid atmosphere you will eventually reach a point, the "dewpoint" wherein the moisture will condense out of that atmosphere in the form of fog, dew, or rain.
Two things must be true for this instance to occur.
1. The windshield surface must be colder than the surrounding atmosphere.
2. The surrounding atmosphere must be at, or very near its dewpoint, relative humidity must be extremely high.
A contributing factor might be some type of "condensation catelyst" in the atmosphere, dust particles, etc.
There is a third possibilty, however unlikely. As the system airflow exits the defrost vents it passes through a pressure gradient. The atmospheric pressure within the vent is ever so slightly higher than just outside the vent opening. Most of us have seen examples of this, a brief period of what appears to be smoke (fog, actually) coming from the A/C vents shortly after we first start up the car.
In the 2001 RX300 the fresh air inlet is opened, and the A/C compressor is automatically activated (although the A/C indicator does not lite) in defrost mode.
The instance described in this post is much more common in a Lexus in the wintertime when the A/C compressor is shut down automatically by the system when/because the outside temperature declines to or very near freezing. In that case the interiro windshield has already been chilled by the 60MPH on-rushing impinging airflow, and now the cabin humidity will begin to rise as the moisture previously condensed out of the atmosphere onto the evaporator vanes begins to evaporate into the system airflow.
But the post was made in July.
Lexus always routes some portion of the system airflow to the defrost vents, even a larger portion in cooling mode. If the setpoint is say, 70 degrees F, the airflow from the defrost vents might be as low as 51F, clearly enough to, over time, lower the temperature of the interior surface of the windshield significantly below that of the cabin atmosphere temperature of 70F.
I should point out that in most Lexus owner's manuals there is a note of CAUTION, warning against operating the system in defrost mode while the system itself is in cooling mode for almost exactly this reason. The only difference being Lexus' concern is regarding condensation on the OUTSIDE due to an artificially cooled windshield surface excountering a hot and humid environment.
The best way I have found to define cooling mode is when the system has AUTOMATICALLY begun to route the airflow from any outlets other than footwell.
My own note of CAUTION.
With regards to defogging or demisting the interior surface of the windshield, Lexus relies SOLELY on the ability of the A/C system to DEHUMIDIFY the system airflow enough that the VAPOR PRESSURE formed by cooled "dried" air flowing over the windshield surface will be always be sufficient to EVAPORATE the condensation from the windshield.
Although the Lexus system is designed to shut the A/C compressor down, automatically at about 35F, it makes no other adjustments or compensations for now not being capable of dehumidifying the airflow whatsoever. Even if the A/C compressor could be restarted manually (it cannot) its ability to dehumidify the already cold incoming fresh airflow is nonexistent.
At this point Lexus leaves it up to the operator to determine, or know, that only HEATED airflow to the windshield will be of any help whatsoever.
As a matter of fact the ability of the A/C system to dehumidify outside incoming airflow that is below about 47F declines precipetesly (no pun intended) as the temperature declines below this point. So, basically, the Lexus driver/operator should always be prepared to intervene with the "automatic" operation of the defrost function if condensation begins to form on the windshield.
ALWAYS TURN UP THE HEAT TO REMOVE CONDENSATION FROM THE WINDSHIELD AND KEEP IT FROM REFORMING!
If the Lexus climate control system has already brought the cabin atmosphere to within a narrow margin, 2-3 degrees F, of the commanded setpoint (70F?), then the airflow to the windshield in defrost mode might be as low as 50F.
Since it is so very likely that in the posted instance the system was already operating in cooling mode (JULY), the only probable solution is to lower a rear window or windows eevr so slightly to allow the stale and humid atmosphere within the cabin an escape route.
AS a future preventative measure it might be a good idea that when the vehicle is parked under shelter the sunroof and/or windows should be left opened. When the vehicle is parked after use of the A/C it is very likely the evaporator vanes are covered with condensed moisture. If the vehicle is parked all closed up then this mositure is trapped within the vehicle for the duration.
I have heard some people suggest turning the A/C compressor off and the blower speed up with the rear windows open about five minutes before shutting the system down for the evening, or whenever.
MY 92 LS has four 12V muffin fans, two within each rear quarter panel, to force cabin exhaust airflow from the car. They are automatically activated when front or rear defrost is used and I can activate them manually if need be.
Everyone seems to be very good at telling us to use the fresh inlet airflow mode to prevent these instances, but what most do not seem to realize is that Lexus, in the name of comfot and quietness, does not allow for airflow to easily exist, exhaust from any of their vehicles.
An open fresh air inlet does very little good if there is no existing airflow, all it will do is slight pressurize the cabin.
May I take the liberty of restating?
"I have noticed this fog/condensation forming on the interior surface of the windshield near the defrost vents."
?????
Condensation forms on the interior windshield surface because that surface is COLD enough to lower the temperature of the humid atmosphere flowing over it to its dewpoint. As you lower the temperature of a humid atmosphere you will eventually reach a point, the "dewpoint" wherein the moisture will condense out of that atmosphere in the form of fog, dew, or rain.
Two things must be true for this instance to occur.
1. The windshield surface must be colder than the surrounding atmosphere.
2. The surrounding atmosphere must be at, or very near its dewpoint, relative humidity must be extremely high.
A contributing factor might be some type of "condensation catelyst" in the atmosphere, dust particles, etc.
There is a third possibilty, however unlikely. As the system airflow exits the defrost vents it passes through a pressure gradient. The atmospheric pressure within the vent is ever so slightly higher than just outside the vent opening. Most of us have seen examples of this, a brief period of what appears to be smoke (fog, actually) coming from the A/C vents shortly after we first start up the car.
In the 2001 RX300 the fresh air inlet is opened, and the A/C compressor is automatically activated (although the A/C indicator does not lite) in defrost mode.
The instance described in this post is much more common in a Lexus in the wintertime when the A/C compressor is shut down automatically by the system when/because the outside temperature declines to or very near freezing. In that case the interiro windshield has already been chilled by the 60MPH on-rushing impinging airflow, and now the cabin humidity will begin to rise as the moisture previously condensed out of the atmosphere onto the evaporator vanes begins to evaporate into the system airflow.
But the post was made in July.
Lexus always routes some portion of the system airflow to the defrost vents, even a larger portion in cooling mode. If the setpoint is say, 70 degrees F, the airflow from the defrost vents might be as low as 51F, clearly enough to, over time, lower the temperature of the interior surface of the windshield significantly below that of the cabin atmosphere temperature of 70F.
I should point out that in most Lexus owner's manuals there is a note of CAUTION, warning against operating the system in defrost mode while the system itself is in cooling mode for almost exactly this reason. The only difference being Lexus' concern is regarding condensation on the OUTSIDE due to an artificially cooled windshield surface excountering a hot and humid environment.
The best way I have found to define cooling mode is when the system has AUTOMATICALLY begun to route the airflow from any outlets other than footwell.
My own note of CAUTION.
With regards to defogging or demisting the interior surface of the windshield, Lexus relies SOLELY on the ability of the A/C system to DEHUMIDIFY the system airflow enough that the VAPOR PRESSURE formed by cooled "dried" air flowing over the windshield surface will be always be sufficient to EVAPORATE the condensation from the windshield.
Although the Lexus system is designed to shut the A/C compressor down, automatically at about 35F, it makes no other adjustments or compensations for now not being capable of dehumidifying the airflow whatsoever. Even if the A/C compressor could be restarted manually (it cannot) its ability to dehumidify the already cold incoming fresh airflow is nonexistent.
At this point Lexus leaves it up to the operator to determine, or know, that only HEATED airflow to the windshield will be of any help whatsoever.
As a matter of fact the ability of the A/C system to dehumidify outside incoming airflow that is below about 47F declines precipetesly (no pun intended) as the temperature declines below this point. So, basically, the Lexus driver/operator should always be prepared to intervene with the "automatic" operation of the defrost function if condensation begins to form on the windshield.
ALWAYS TURN UP THE HEAT TO REMOVE CONDENSATION FROM THE WINDSHIELD AND KEEP IT FROM REFORMING!
If the Lexus climate control system has already brought the cabin atmosphere to within a narrow margin, 2-3 degrees F, of the commanded setpoint (70F?), then the airflow to the windshield in defrost mode might be as low as 50F.
Since it is so very likely that in the posted instance the system was already operating in cooling mode (JULY), the only probable solution is to lower a rear window or windows eevr so slightly to allow the stale and humid atmosphere within the cabin an escape route.
AS a future preventative measure it might be a good idea that when the vehicle is parked under shelter the sunroof and/or windows should be left opened. When the vehicle is parked after use of the A/C it is very likely the evaporator vanes are covered with condensed moisture. If the vehicle is parked all closed up then this mositure is trapped within the vehicle for the duration.
I have heard some people suggest turning the A/C compressor off and the blower speed up with the rear windows open about five minutes before shutting the system down for the evening, or whenever.
MY 92 LS has four 12V muffin fans, two within each rear quarter panel, to force cabin exhaust airflow from the car. They are automatically activated when front or rear defrost is used and I can activate them manually if need be.
Everyone seems to be very good at telling us to use the fresh inlet airflow mode to prevent these instances, but what most do not seem to realize is that Lexus, in the name of comfot and quietness, does not allow for airflow to easily exist, exhaust from any of their vehicles.
An open fresh air inlet does very little good if there is no existing airflow, all it will do is slight pressurize the cabin.
09-29-01, 12:50 PM
#6
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Changed opinion...
I just went out and checked out my 2001 GS300 and my 2001 RX300. With the climate control systems in any mode except footwell only or footwell and defrost combined I do not believe there is enough airflow to the interior windshield surface, even with the blower on high, to have caused your problem. Certainly not in the short term, it would likely take hours for this to happen in anything other than either of these modes.
But it makes little sense that you might be operating the system in (manual) footwell mode during July, in the summertime (in the northern hemisphere anyway). So is it possible that due to some past windshield fogging experience you have developed the habit of running it in mixed (footwell/defrost) mode in an attempt to alleviate the fogging problem?
On a hot day the predominant system mode would be to cool the cabin and regardless of how you (manually) routed the airflow you would still get chilled airflow, quite possibly moreso at the defrost outlets. Are you by chance experiencing this problem just after picking up a group of sweaty soccer players?
So with this new input I want to revise my earlier suggestions.
1. Did the dealer check for the possibility that the defrost outlet vents are stuck open somehow?
Just as the Lexus CAUTION note states, if cold airflow is routed to the interiro surface of the windshield on a hot and humid day the likelihood of condensation forming on the outside of the windshield increases dramatically. However unlikely, there are climatic circumstances wherein it might form on the inside first.
I just went out and checked out my 2001 GS300 and my 2001 RX300. With the climate control systems in any mode except footwell only or footwell and defrost combined I do not believe there is enough airflow to the interior windshield surface, even with the blower on high, to have caused your problem. Certainly not in the short term, it would likely take hours for this to happen in anything other than either of these modes.
But it makes little sense that you might be operating the system in (manual) footwell mode during July, in the summertime (in the northern hemisphere anyway). So is it possible that due to some past windshield fogging experience you have developed the habit of running it in mixed (footwell/defrost) mode in an attempt to alleviate the fogging problem?
On a hot day the predominant system mode would be to cool the cabin and regardless of how you (manually) routed the airflow you would still get chilled airflow, quite possibly moreso at the defrost outlets. Are you by chance experiencing this problem just after picking up a group of sweaty soccer players?
So with this new input I want to revise my earlier suggestions.
1. Did the dealer check for the possibility that the defrost outlet vents are stuck open somehow?
Just as the Lexus CAUTION note states, if cold airflow is routed to the interiro surface of the windshield on a hot and humid day the likelihood of condensation forming on the outside of the windshield increases dramatically. However unlikely, there are climatic circumstances wherein it might form on the inside first.
09-29-01, 05:28 PM
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I have exactly the same problem and irritates me, too. Usually it happens on a nice sunny day in the summer, when there is no need for AC and I can drive with the windows half-down. The windshield becomes visibly foggy. The only way to get rid of it is to turn the AC full blast for about 1 min and it goes away. It's good for another 10 min, then it accumulates again. Never had this problem before in any car I drove before.
RX is my first luxury car and I like it. I am following this board regularly. What surprises me is how many imperfections it has which should not be the case for the car of that class and money. The things that should not be discussed at all like inside windshield fog.
RX is my first luxury car and I like it. I am following this board regularly. What surprises me is how many imperfections it has which should not be the case for the car of that class and money. The things that should not be discussed at all like inside windshield fog.
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09-29-01, 09:37 PM
#8
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Self defeating practice..
You run the A/C briefly, it dehumdifies the airflow and that defogs the windshield. When you subsequently stop the A/C compressor it takes about ten minutes for the moisture condensed onto the evaporator, just minutes ago, to start evaporating into the system airstream. Shortly thereafter the windshield starts to fog up again....
Repeat above sequence as required.
Either use the A/C system continuously or not at all.
You run the A/C briefly, it dehumdifies the airflow and that defogs the windshield. When you subsequently stop the A/C compressor it takes about ten minutes for the moisture condensed onto the evaporator, just minutes ago, to start evaporating into the system airstream. Shortly thereafter the windshield starts to fog up again....
Repeat above sequence as required.
Either use the A/C system continuously or not at all.
09-30-01, 09:52 AM
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Originally posted by willard west
Self defeating practice..
You run the A/C briefly, it dehumdifies the airflow and that defogs the windshield. When you subsequently stop the A/C compressor it takes about ten minutes for the moisture condensed onto the evaporator, just minutes ago, to start evaporating into the system airstream. Shortly thereafter the windshield starts to fog up again....
Repeat above sequence as required.
Either use the A/C system continuously or not at all.
Self defeating practice..
You run the A/C briefly, it dehumdifies the airflow and that defogs the windshield. When you subsequently stop the A/C compressor it takes about ten minutes for the moisture condensed onto the evaporator, just minutes ago, to start evaporating into the system airstream. Shortly thereafter the windshield starts to fog up again....
Repeat above sequence as required.
Either use the A/C system continuously or not at all.
I agree with everything you say, but how to deal with this situation: nice and warm sunny day, I start the car, the AC is off, roll down the window, then in a few minutes I see the mist on the interior windshield. At that moment, I did not use AC at all.
What sequence are you talking about to repeat.
Thanks.
09-30-01, 02:31 PM
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How long was the RX parked, and did you close it up or let it air out thoroughly, from the previous time you drove it and did use the A/C?
My 92 LS would do exactly the thing you describe until I learned to open the sunroof in the garage overnight so the moisture "captured" from that day's A/C operations could evaporate and "migrate" out of the cabin.
My 92 LS would do exactly the thing you describe until I learned to open the sunroof in the garage overnight so the moisture "captured" from that day's A/C operations could evaporate and "migrate" out of the cabin.
10-01-01, 02:46 AM
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Originally posted by wwest
How long was the RX parked, and did you close it up or let it air out thoroughly, from the previous time you drove it and did use the A/C?
My 92 LS would do exactly the thing you describe until I learned to open the sunroof in the garage overnight so the moisture "captured" from that day's A/C operations could evaporate and "migrate" out of the cabin.
How long was the RX parked, and did you close it up or let it air out thoroughly, from the previous time you drove it and did use the A/C?
My 92 LS would do exactly the thing you describe until I learned to open the sunroof in the garage overnight so the moisture "captured" from that day's A/C operations could evaporate and "migrate" out of the cabin.
???
10-01-01, 10:00 AM
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A few suggestions then...
When you start up the Lexus and the engine water jacket is cold, below about 130F, Lexus "baffles" (presumably cold) incoming airflow but automatically putting the system in "defrost", forcing incoming airflow to do a U-turn, thus restricting its velocity. They do this so you will not be discomforted by cold air flowing out of the system early in the morning.
I'm pretty sure you can over-ride this automatic function by simply activating the footwell mode as soon as you start the car.
On the asumption that I am correct and your problem is an extremely high relative humidity atmosphere within the system plenum, it would help to be especially certain the system is in "fresh" mode, not recirculate, and then turn up the system blower to high with the rear windows slightly open for the first few minutes after you start out in the morning.
A couple of points of CAUTION.
Sometimes you may be using A/C without knowing it. My 2001 RX activates the A/C compressor automatically in defrost/defog mode without turning the A/C "in use" indicator on.
Not sure about the RX, but most LS's in automatic mode can have the system in recirculate (at least partially) even though the "fresh" indicator is on.
Lexus relies exclusively on the A/C compressor (the system's ability to dehumidfy the airflow) to remove condensation and prevent more condensation from forming on the interior surface of the windshield. This capability becomes more and more marginal as the outside air temperature has declined below about 45-50F, and it is completely non-existent just above (35F{?}) and below freezing temperatures. The Lexus system automatically shuts down the A/C compressor at about 35F and it CANNOT be manually restarted below that temperature.
The best procedure to follow at or near these temperatures is to turn up the cabin temperature setpoint while using the defrost function, this will have the effect of, not only removing the initial condensation, but raising the interior windshield temperature above the dewpoint of the cabin atmosphere.
Most school kids know that the process of evaporation will further cool the object from which the moisture is removed. Lexus doesn't seem to know that. So if you rely on their system exclusively, when you return the system to "normal" use (from defrost) the windshield has now been further chilled from the point it was when the condensation began to form, and the cycle will very likely repeat.
Good Luck.
When you start up the Lexus and the engine water jacket is cold, below about 130F, Lexus "baffles" (presumably cold) incoming airflow but automatically putting the system in "defrost", forcing incoming airflow to do a U-turn, thus restricting its velocity. They do this so you will not be discomforted by cold air flowing out of the system early in the morning.
I'm pretty sure you can over-ride this automatic function by simply activating the footwell mode as soon as you start the car.
On the asumption that I am correct and your problem is an extremely high relative humidity atmosphere within the system plenum, it would help to be especially certain the system is in "fresh" mode, not recirculate, and then turn up the system blower to high with the rear windows slightly open for the first few minutes after you start out in the morning.
A couple of points of CAUTION.
Sometimes you may be using A/C without knowing it. My 2001 RX activates the A/C compressor automatically in defrost/defog mode without turning the A/C "in use" indicator on.
Not sure about the RX, but most LS's in automatic mode can have the system in recirculate (at least partially) even though the "fresh" indicator is on.
Lexus relies exclusively on the A/C compressor (the system's ability to dehumidfy the airflow) to remove condensation and prevent more condensation from forming on the interior surface of the windshield. This capability becomes more and more marginal as the outside air temperature has declined below about 45-50F, and it is completely non-existent just above (35F{?}) and below freezing temperatures. The Lexus system automatically shuts down the A/C compressor at about 35F and it CANNOT be manually restarted below that temperature.
The best procedure to follow at or near these temperatures is to turn up the cabin temperature setpoint while using the defrost function, this will have the effect of, not only removing the initial condensation, but raising the interior windshield temperature above the dewpoint of the cabin atmosphere.
Most school kids know that the process of evaporation will further cool the object from which the moisture is removed. Lexus doesn't seem to know that. So if you rely on their system exclusively, when you return the system to "normal" use (from defrost) the windshield has now been further chilled from the point it was when the condensation began to form, and the cycle will very likely repeat.
Good Luck.
10-01-01, 10:56 AM
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wwest,
Thanks for you ideas. It sounds great. The only problem I don't have any desire to start learning all the intricacies of the A/C system. Actually, I'm talking to Lexus and I think they should monitor our board and take our complains into consideration or, at least, give us their opinion. I'm a just a driver. What I need is to start my car at nice weather (let's say 65-75F), roll down my window half way and enjoy my ride. And I don't want to see any mist on the interior of my windshield, if I don't use the AC. As I mentioned before, I never saw such a thing in even very cheap cars. Too bad such a beuatiful car has such annoying problems.
Thanks for you ideas. It sounds great. The only problem I don't have any desire to start learning all the intricacies of the A/C system. Actually, I'm talking to Lexus and I think they should monitor our board and take our complains into consideration or, at least, give us their opinion. I'm a just a driver. What I need is to start my car at nice weather (let's say 65-75F), roll down my window half way and enjoy my ride. And I don't want to see any mist on the interior of my windshield, if I don't use the AC. As I mentioned before, I never saw such a thing in even very cheap cars. Too bad such a beuatiful car has such annoying problems.
10-01-01, 04:30 PM
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I initially reported this problem to Lexus in the fall of 91, just after I purchased my first Lexus. I sued them under the Lemon Law in early 93 and lost.
I can't imagine that someone at Lexus doesn't care, but they certainly haven't shown any interst in improving the system in all of that time.
To be fair to Lexus, their climate control system is designed and manufactured by DENSO USA, formerly NipponDenso. Anytime you find a car with an automatic climate control system by Denso, you will see thia very same problem, it isn't unique to Lexus or Toyota.
I can't imagine that someone at Lexus doesn't care, but they certainly haven't shown any interst in improving the system in all of that time.
To be fair to Lexus, their climate control system is designed and manufactured by DENSO USA, formerly NipponDenso. Anytime you find a car with an automatic climate control system by Denso, you will see thia very same problem, it isn't unique to Lexus or Toyota.