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Official Rx330 C-best Settings

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The Lexus series has a very high propensity to fog over the windscreen suddenlt and spontaneously with no obvious warning to the driver or passengers. A recent J D Power survey indicates sudden windshield fogging as the second most common owner complaint within the US.

The article said that this effect/complaint is clearly more predominant in cars of Japanese design origin.

One of the primary causative factors is the fact that Lexus/Toyota's climate control design supplier is NipponDenso, in the US known as Denso USA. Denso has several design flaws inherent in their system.

1. they operate the A/C compressor all year around.

2. In order to keep the fuel economy within reason they severely restrict the outflow of conditioned cabin atmosphere.

3. They seemingly are not aware of the fact that human body comfort is as much a result of MRT (Mean Radiant Temperature) as it is local air temperature. The result of this lack of knowledge is that the system will automatically switch to cooling mode, airflow predominantly form the face and upper body outlet vents and as much as 20F lower than the temperature setpoint (brrrrrrr....). The side effect of this "switch" is the lack of warming airflow to the windshield on a cold and possibly humid day resulting in fogging of the windshield.

There are several procedures one can use to avoid these problems.

Have the dealer set the C-best options such that the A/C compressor is NOT "linked" to the use of automatic mode or defrost/defog/demist mode. These are two separate C-best settings/options. Also have the dealer set the system such that it always operates in footwell outlet airflow mode ( heating mode, with substantial warm airflow to the interior surface of the windshield) unless you manually over-ride it into cooling mode.

I would also advise you that after having used the A/C during the day then open the windows in the garage overnight so that the thin film of moisture left on the A/C evaporator due to that operation car dry out and not contribut to windshield fogging shortly after startup the next morning.

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This is for the '04 330 only. There are some things that are the same, some that are different between the two. You can log onto the Toyota/Lexus tech site and get yours though.

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