Climate Control

[rwerner]

I have a 2004 RX330. The climate control appears to not work correctly. Today it was 63 degrees outside and the car is set for 72 degrees inside yet it continues to blow cold air if the air conditioning is on. My experience with an Infinity is you should be able to set the inside temperature and forget about it. The air conditioning compressor should turn off when the interior is below the setting. I brought this to the attention of the dealer on my 1000 mile check up and they indicated that everything is working correctly. Any comments would be appreciated.

[wwest]

The Lexus climate control has several design flaws originating from the very beginning in 89.

Toyota and Lexus uses a design by NipponDenso as does most asian manufacturers. Of more recent vintage Denso USA, a subsiderary of NIpponDenso has been bringing those same flaws into the US market.

First, they apparenty have no realization of what constitutes human comfort in cooler or colder weather conditions. Our bodies are greatly influenced by radiant heating effects, or really, lack thereof, in wintertime conditions. The COLD outside wintertime surrounding landscape can have a very chilling effect on our bodies, especially at night.

At the same time Denso seems to be very proud of an asspect of their design that contributes heavily to your discomfort in the wintertime. Denso claims a uniqueness to their climate control design in that it "biases" the system to aways provide fresh airflow to the upper areas of the passenger cabin while providing recirculating airflow nearer your feet or below the "beltline.

According to Denso once the overall cabin temperature has risen to very near the temperature setpoint, say 72F, the upper level airflow will be as much as 20F below the setpoint while the lower airflow will be warm enough to make up the difference.

Their primary argument for this uniqueness seems to be that it tends to help keep the windshield and windows free of condensation. Somehow they seemed to have justified this position by claiming that we are more comfortable with this layered airflow model.

And speaking of windshield condensation therein is the most astounding and hazardosu flaw in the design. With the advent of the use of the new lower efficiency refrigerant in the early ninties the A/C evaporator had to be made a lot more complex in order to have sufficient cooling cooling capability in AZ at 100F on a really hot bright sunny day.

When you turn off the A/C at any time and for any reason, there will always be a thin film of moisture on its surface, thin enough that will NOT drain away. In the southern area of the US that often leads to the formation of mould and mildew, that horrid dirty gym socks smell. In the more northern areas of the US, or in the wintertime, its that very same moisture that leads to sudden early morning fogging over of the windshield. Or actually, anytime the A/C is cycled off and that thin film of moisture begins to evaporate into the incoming airstream.

The whole windshield fogging problem is exaserbated greatly by the fact that Denso seemingly hasn't a clue as to what is needed to quickly clear a fogged over windshield and/or keep the windshield cleart of fogging.

First, at the same time the system switches modes from heating, footwell airflow predominantly, to cooling mode (the more to discomfort YOU!), mixed outlet airflow, foot and panel (automatic function as the cabin temperature rises to setpoint), and then to panel outlets only, IT STOPS ALL WARMING AIRFLOW to the windshield. A windshield t hat will now be growing colder by the moment due to 60MPH COLD airflow impinging on the exterior surfrace.

Additionally, the Denso design relies EXCLUSIVELY on the ability of the A/C to dehumidify the incoming airflow to clear the windshield of condensation when that time arrives. That's the reason your A/C continues to operate automatically even below your need of the use of it for cooling purposes. When, or if, you activate the windshield defrost/defog/demist function of your Toyota or Lexus climate control system you will instantly get airflow to the windshield that is approximately 20F below the setpoint level. Airflow that may, or may NOT, have been dehumidified by the A/C.

The efficiency of the A/C for dehumdifying the incoming airflow is very much dependent on the relative humidity of the INCOMING outside airflow. Below about 45F it is unusual for the humdity to be high enough for the A/C to be effective for this purpose. As the outside temperature continues to decline the ability of the A/C to accomplish any dehumidification at all becomes even less probable. Until at about 35F OAT the system itself will shut down the A/C system due to complete non-functionality belwo this temperature.

One would think that the Denso engineers would be bright enough to know, recognize, that with the decling efficiency of the A/C for defogging nthe windshield matters of safety would dictate the sue of an alternative method. And there is a readily available aternative method, one that most drivers have relied upon virtually since the invention of the enclosed cabin. HEAT.

But no, I have been told that the Denso (more likely a Lexus engineer OVER_RIDE) engineers decided that exceedingly warm, or even HOT, airflow to the windshield surface would be too horribly discomforting to the front seat passengers.

So it really doesn't matter to Lexus if you are killed in the process of trying to steer a direction with your windshield thoroughly and completely fogged over. NOT a problem they concern themselves with.

But, go back to the dealer and tell them you wish to have the system reset so the A/C does not operate unless you specifically wish. And at the same time have them disable the A/C "link" to the defrost/defog/demist mode.

And by the way, the A/C will normally activate in the defrost/defog/demist mode without the indicator illuminating.

Without the A/C operating in the wintertime you will be a lot less likely to encounter windshield fogging, certainly not of the type caused by thye A/C itself. But if you do encounter windshield fogging the very best solution, ALWAYS, is turn up the heat to max, the blower should follow automatically, and then activate the defrost/defog/demist function. It doesn't hurt to lower a rear window slightly to flush the mositure you just brought in with those sweaty wet snow skiiers.

The Lexus series is exceedingly well sealed and insulated, double door seals, etc, not only for your personal comfort but to also increase the MPG economy rating. In the summertime the less "conditioned" airflow that escapes the less the A/C compressor operates. Each Lexus does have the required airflow "exhauster port" but it's generally mounted in a location resulting in substantially reduced incoming airflow than most of us would desire, especially in the wintertime and high cabin humidity for some reason. Those damn snow skiiers again.

And now to prevent further condensation keep the windshield interior surface warmed by over-riding the system's propensity to go into "cooling" mode (no warming airflow to the windshield) automatically.

Good reading at:

http://www.airsept.com/eed.html

[JPI]

Is this a copy and paste deal? Back to the question. Your A/C compressor won't completely shut down when it get to the preset temp. But it will reduce the amount of cool air blowing out. There are a lot of bugs in the RX330 but this is not one them.

www.jpimportz.org

[wwest]

To answer the original question more directly.

The dealer is correct, your climate control is operating exactly as designed. In your case the continuing operation of the A/C is certainly not "on point". The problem you relate to is due to the fact that the Lexus design automatically switches to "cooling" mode once the cabin temperature approaches your 72F setpoint, even with outside temperatures at sub-zero.

In fully automatic mode, as the cabin temperature climbs the system will automatically switch from footwell system outlet airflow only, first to combined footwell and panel outlets at about 5-8F below setpoint, and then panel outlet only as it rises to within 2-3F of setpoint. I refer to these last two modes as "cooling" because that is effectively waht it does. The A/C is operating so this airflow will be fairly dry. Even if it were at the temperature setpoint it would still feel like a cooling breeze to our body.

Just like the rest of the human race, you find this very discomforting.

Join the crowd.

I cannot tell you why Lexus doesn't understand human metabolism. I even filed a lawsuit back in 93 over this very issue. Arising out of the fact of switching to cooling mode on the coldest day in the dead of winter is the fact that in this mode the interior windshield surface temperature is allowed to decline to within the DANGER zone.

If Lexus were to properly design the system in recognition of your discomfort factor then the system would remain in heating mode during COLD weather and the windshield would continue to be heated thus helping to prevent instances of sudden windshield fogging.

I lost.

To close: The fact that the A/C continues to operate is not really pertinent to the heating/cooling mode switch. Just like the Lexus, my 2001 Porsche 996 also keeps the A/C running all the way down to about 35F. The big difference for the Porsche is that if the outside temperature is on the cool or cold side it will always remain in heating, footwell, air distribution mode. Like the Lexus, in this mode some airflow is diverted to the windshield to keep it warmed and well above dewpoint. But unlike the Lexus, if the defrost/defog/demist function is activated the windshield gets blasted with HOT and dry (assuming the relative humidity is within a range wherein the A/C can accomplish this) airflow, even on the hottest day of summer.

Cut and paste: No, on line in real time. Well versed on the subject matter.

[csg103]

I don't know if this has anything to do with this topic but here goes:

My car is 2001-bought new. Since last November, the Air light flashes on and off and basically shut off during a heavy rain-the dealer told me that when the hose gets wet, this is normal.

But what worries me more is that the car now feels like it's in low and the high temp light goes on even though the needle remains in the middle. I have to shut off everything in order for the car to run normally. I live in Florida so this is not a once in a while occurance. I've taken the car in twice and basically been given a pat answer. It happened again Sunday and I was on a rather long drive with my child in the car which worries me. This cannot be normal. I'm going to contact the service manager at this point but was wondering if anyone had any idea what is going on??

Thanks,

Cindee

[wwest]

It's the serpentine accessory drive belt that often slips when wet, say in a heavy rain, and the dealer is correct that is normal.

Sounds like it's the transmission fluid that's over-heating and turning on the "icon" not the engine water jacket which is what the guage indicates.

I would park it immediately and have the dealer tow it to his shop.

If you continue to drive the dealer may justifiably hold you responsible for some level of the damage.

[DJF]

I've got the same problem with my RX330. I had a SC300 (1995) and the climate control was perfect. The RX330 always trys to freeze us to death. This problem is worse in moderate weather - temperatures in the 50s & 60s. There are 2 general reasons for this.

1. The sensor (sniffer) port for the climate control is located opposite the drivers right knee, low down on the dash (you'll see a small vent there - about 1/2 inch square). Air is sucked in by a small fan and sampled for temperature and, based on that, the systems raises or lowers the temperature of the incoming air. The next time that you've been driving for a while, touch the area around this port and you'll find that it is quite warm. It is picking up heat from your right knee, which is typically only an inch or 2 away, and also from equipment within the dash. Therefore, the air that it is sampling is not representative of the cabin temperature - just you knee temperature. My SC300 had the port in the center of the dash, away from body parts, and there was no problem with maintaining a comfortable temperature.

2. In moderate weather, when the temperature is set below 76, the heat mixer door does not open after the interior of the car has warmed up to what the systems thinks is the right temperature. If you adjust the temperature to 76, or above, the door opens and much more warm air is mixed in.

What can you do about this? Not much but work around it. There's nothing that Lexus can do to fix it - it's simply a faulty design. The workarounds that we've found to work are:

a. Treat the temperature setting numbers as something other than degrees fahenheit. 72 does not mean 72 degrees in the cabin. Therefore, just turn it up until you're comfortable, even if that's 80. We've found that a setting of about 75-76 is most comfortable and probably is about 70 in the cabin.

b. Don't leave the Mode on automatic. Use one of the settings where air is forced to the floor and either the windshield or the dash vents. This reduces the amount of air flowing out of the dash vents so that it's less annoying and the air coming out of the floor vents is warmer.

c. Unless it's hot in the car, manually turn off the A/C.

Doing the above, we've made some long trips in relative comfort.

[wwest]

The very best thing you can do once the system switches to cooling in automatic mode is to simply return it to footwell air outflow mode. If you raise the temperature you will end up being discomforted from over-heating and then when the system reaches the new setpoint is will again switch to cooling mode.

A possible alternative, just thought of, is to lower a rear window slightly so the cabin air temperature never approaches the setpoint.

But at the very core, the problem remains that the NipponDenso engineers haven't a clue regarding human body comfort effects. All warm bodies continually radiate heat OUTWARD, including ours. IN the summertime when the surrounding "landscape" is predominantly warm or hot the "net" of the outward bound radiant heat versus that recieved keeps us reasonably comfortable or we might need an A/C for cooling.

In the wintertime, or in the wee hours of the morning, driving along in that glass greenhouse we call a car the surrounding landscape to which our body is constantly exposed readily absorbs the radiant heat from us but gives virtually nothing in return.

The really bad news is that our "designer" decided for some reason that raising the air temperature dramatically around our bodies in this circumstance, to make up for radiant heating losses, would only further discomfort us.

Raising the temperature setpoint a few degrees will help but the very best thing to do is manually over-ride the system into footwell mode.

And bye-the-bye, leaving it in footwell mode will also serve to delay or prevent any instances of windshield fogging or even hazardous sudden windshield fogging. After 15 years of production Lexus has finally figured out this latter point, see the operational modes of the new RX330 regarding windshield fogging prevention.

Idiots (Lexus, Toyota, NipponDenso, Denso).