Last post on Jun 13, 2013 at 11:06 AM
You are in the Lexus LS 400/LS 430
What is this discussion about?
Lexus LS 400, Lexus LS 430, Sedan
Apr 16, 2001 (11:29 am)
First let me say that I firmly believe that the LS400, 430 is the best car one can buy for the money there is today.
But ALL of the Lexus vehcicles share two common defects. First, the interior surface of the windshield will suddenly fog over, spontaneously, in certain climatic conditions. AND, in addition, they all lack the ability to QUICKLY remove condensation from the interior windshield surface.
Quietness, a danger!
About half of the overall industry, and the majority of the Japanese industry, use climate controls designed and manufactured by Denso USA, or NipponDenso. In any car in the OTHER half when you activate the defog or demist function you instantaneously get airflow to the windshield which has been "dehumidified" by raising, heating, it. Sometimes this airflow will be further dehumidified through the use of the A/C compressor. The A/C compressor CANNOT be used to dehumidify airflow below 32F OAT and SHOULD NOT be used below about 47F, where the liklihood of positive effects has declined precipetously.
In a Lexus when the A/C compressor is shut down inadvertantly, or unknowingly, by the operator, or automatically by the system design once the OAT declines to 32F, in a cold wintertime climate then there is a very high probability of the windshield fogging over shortly thereafter.
Throughout the winter of 91-92 I had numerous instances of instantaneous fogging over of the windshield. Some of these, granted, were on a mountain pass with quite cold temperatures, not something I would refer to as a hellhole, but extreme from the norm for the Seattle area. But I also had it happen when the cliamte was fairly temperate. One of the things that puzzled me was that the Lexus customer service personnel kept advising me to be sure the system was in flow-through mode. They kept saying, yes, I know the flow-through indicator is on, but press the button anyway to be sure.
It was only after I purchased the shop manuals that I began to understand the reasons behind their instructions. On the 92 LS there are two indicator lights one for recirc and another for flow-thru, a binary function, or so I thought!
It turns out that if the system is in fully automatic mode then the condition of these indicators can be meaningless. In fully automatic mode the system "meters" the amount of incoming airflow from the outside as one of the parameters for controlling, regulating, interior
temperatures. Quietness rules. In wintertime when the outside air temperature is quite low the amount of this cold air allowed to enter the cabin might be quite low. It isn't that the system doesn't have the capacity to heat this cold airflow to a comfortable level, I believe it is because a higher level of airflow means a higher blower speed and more cabin noise.
What I didn't understand, and something Lexus didn't want to tell me in a direct fashion, was that my 92 Lexus's inlet airflow controls had two modes, automatic and manual, but no indication to the operator of which mode was actaully active at any given time. IT turned out that what they were saying to me was, "if you want to be sure the system to be in actual flow-through mode, you MUST depress the flow-through button each and every time you start the car, otherwise it "might" be in automatic mode and that circumstance "might" allow the cabin humidity to rise to dangerous levels.
In 1993 I had a Lexus expert testify in a court of law that the mistake I made was not manually re-activating the A/C upon the occurance of this circumsatnce, the A/C being shut down automatically because the OAT declined below 32F. Today I have very little doubt that he knew EXACTLY what was wrong with my Lexus.
Here it is 2001 and MB now has a humidity detection system which is used to control, meter, fresh air into the cabin such that the interior humidity level does not reach dangerous levels. MB is also one of the cars, as are most cars of eurpoean manufacture, that is designed to use HEAT to remove condensation.
Read the posts under defog/demist gone awry for more detail on this subject.
Second design flaw.
The Lexus Climate control, in fully automatic mode, will automatically switch the airflow routing mode from footwell to mixed and then to upper body once the interior cabin ambient air temperature approaches, then reaches, the temperature set by the operator. EVEN IN THE DEAD OF WINTER, with two feet of snow everywhere around and sub-freezing outside temperatures.
Almost everyone, and certainly most HVAC engineers, have known for many, many years that human body temperatures are very greatly affected by the Radiant temperatures of surrounding objects.
Radiant temperature effects contribute very greatly to human body comfort. The atmosphere surrounding our body can be a very comfortable 72F and we will still feel, no, be chilled, if the objects "in view" of our bodies are cold.
TRW has just announced that by 2004 vehicles for which they supply climate controls will have the ability to measure radiant heating effects and adjust the system accordingly.
I would have thought that in the meantime Lexus designers would have the good sense to know that if their own outside air temperature sensor indicates that the outside air temperature is COLD then it would be discomforting to have the system airflow routed to your face or upper body.
And, oh, by the way, Lexus "system" outlet airflow is not fully "mixed", some of the airflow which has passed through the A/C evaporator (and possibly dehumidified also) bypasses the heater core and is routed directly to the face and upper body outlets. If you have by chance noticed that the airflow to these outlets seems cooler that the simultaneous airflow to the footwell then you are correct, the footwell airflow will be as much as 20F warmer.
That is also what contributes to the rapid and intermittent fogging over of the windshield.
But if we keep our mouth shut about our likes and dislikes, and about what we believe are actual defects, how will Lexus know to improve the breed?
Apr 16, 2001 (1:27 pm)
wwest - the only model you reference is a 10 year old LS and some court case in '93... perhaps things have improved since then?
I've *NEVER* experienced a fogged windshield or uncomfortable airflow in either of my Lexus vehicles. One's a '99 (RX300) and the other is a 2000 (GS400).
I take it you took Lexus to court in '93 because you felt your car was dangerous, or was this related to an accident where you felt Lexus was at fault (perhaps legitimately, when Lexus was building cars 10 years ago)?
Apr 16, 2001 (1:38 pm)
Never experienced "sudden" fog over of the front interior windshield either. It does fog up sometimes when it's raining or cold outside, and simply pressing the front defrost button quickly clears up the windshield on both 1995 ES300 & 2000 LS400. And my Acura 2K 3.2TL fogs up in basically the same situations.
Apr 16, 2001 (1:55 pm)
Sedans and Women's Auto Center Message Boards
Apr 16, 2001 (2:24 pm)
Apr 16, 2001 (2:35 pm)
flint350 - I still monitor the 'high-end' board but won't be posting after seeing arcoates' (who started the forum) thin skin and the other endless flaming among people there, particularly from merc1 who doesn't even own a Mercedes.
I don't mind spirited discussions, but when it gets into personal attacks, it becomes futile.
Apr 16, 2001 (2:45 pm)
My brother in Tn has the 92, a fellow employee has a 95 LS and I currently have a 2000 GS300 and a 2001 RX, traded up from a 2000 RX for the VSC, Trac, and HID.
And yes, I have several experiences with the 92 that I would deem hazardous, in the extreme. I have made several modications to the 92 that I think are important.
1. I moved the OAT sensor into the front of the right front wheel well where it is not subject to the radiant heat from the engine cooling radiator. I notice many manufacturers are now mounting this sensor on the drivers side rear view mirror. None of this solves the problem of the A/C operating unduly after the car is stored overnight in a relatively warm garage. I saw one post recently wherein an owner (GM) was complaining about an OAT indication that didn't read true until he had driven a few miles each morning, undoubtedly a (mis)step in the right direction.
2. I added a switch and 2800 ohm resistor in series with the OAT sensor such that in wintertime I can actuate the switch and at any OAT below 47F the system will get a false reading of below 32F and NEVER activate the A/C compressor. There was an unexpected pleasant result from this. The cabin warms up much quicker each morning becuase the system "thinks" it is 15F colder outside than it actually is.
3. I added a switch in series with the interior temperature sensor such that by operating this switch I add about 200 ohms to this sensor, This causes the system to immediately increase the exit air temperature if I have need to quickly defog/demist the front windshield. Lexus uses the A/C system compressor EXCLUSIVELY to dehumidify the airflow and thus help prevent and remove condensation from the interior windshield surface. The liklihood of the A/C being effective at doing this is very low below about 45-50F, and non-existent once Lexus itself automatically shuts down the A/C compressor (It canot be manually re-started, and it would still be useless even if one could) when the OAT declines below 32F.
Lexus provides ABSOLUTELY no back up defog/demist system other than the A/C compressor. As for as I know any manufacturer that does not use the Denso USA HVAC design use HEATED airflow, some in the EXTREME (in conjunction with the A/C above 47F), to decrease the relative humidity and thus help to remove condensation from the windshield.
4. I added four 12V muffin fans, two within each rear quarter panel, in a fashion such that when activated they serve to quickly extract (humid) cabin air. If I see even a wisp of condensation begin to form on the windshield I immediately activate both of these (3,4) switches and then the front defog function. Activating 3 will cause the system to "think" the cabin temperature is far below setpoint and it will then automatically, and quickly, increase the exit airflow temperature and the blower speed. All of this together resulting in lots of heated airflow to a (likely COLD) windshield which has just begun to fog over. Activating switch #4 aids in quickly removing the evaporated moisture and humidity from the car's atmosphere. The extraction fans also automatically activate when the rear window defrost function is used.
5. When I park the car in the garage at night I ALWAYS crack the sunroof open, regardless of season, so that all of the moisture condensed onto the evaporator vanes will not be still "trapped" within the cabin when I start out the next morning. I recently noticed that Saturn starts up and runs the system blower about ten minutes after shutdown for this same reason.
I have the Lexus shop manuals for both my 2000 GS and the 2000 Rx and I have found no indication that the climate control design has been changed in any manner of these concerns. I have not made any of these changes to the GS becuase we really do not plan to use it all that much in wintertime. I have added the OAT switch and resistor to the RX to surpress the undue operation of the A/C compressor, and I do plan to add the muffin fans soon. Since increasing the temperature setpoint on the RX simply involves a quick clockwise "flick" of a rotary knob I don't see the need for a switch for that functionality.
Apr 16, 2001 (3:10 pm)
Montana, ND, SD
Given the rather sparse populations of these states, I can understand there being no Lexus dealerships, but does that also mean there are not many Lexii driven through or around in these states?
My 92 LS was there, Glacier Park, central Montana, three or four times, the 2000 GS twice already, and the 2000 RX once.
But I don't remember having any complaints specific to these areas, or any complaints about Lexus operation in these areas at all for that matter.
Having quite thoroughly read an accident report from KY wherein two people died after mysteriously leaving the roadbed/freeway on a bright and sunny but cold day I have to wonder if the instantaneous windshield fogging instance might have played a hand in that.
Browse the NHTSA consumer complaints for Toyota and Lexus and windshield fogging or lack of adequate defogging capability, or just search for instances of windshield fogging.
I suspect that the most common occurances of this problem will be found to be circumstances wherein the vehicle is driven, continuously, no stops, from a relatively warm, 45-65F, possibly humid area, into an area of temperatures below 37F, basically colder climates and thus lower humidities predominate.
And yes, the further north you travel, the more likely you will encounter these circumstances.
Fate IS the Hunter!
Apr 16, 2001 (7:57 pm)
okey dokey then... switching subjects since I'm no expert on muffin fans (?) and inserting resistors into climate control systems...
I have seen a few new LS430s on the road, and I must say the look is growing on me, particularly the side and rear views.
I've only seen silver ones on the road so far!
But the look is definitely growing on me.