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'98 Es300 Climate Control

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I'm a new ES300 owner and have a question about the climate control. It's in the mid-30s outside and if I press the "auto" button with the temp set at 78/79 the "AC" light illuminates. It's easy enough to turn off but I can't figure out why on earth the AC would try and come on when it's cold out and I have the temp set high. Am I doing something wrong? Any ideas?

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I'm a new ES300 owner and have a question about the climate control. It's in the mid-30s outside and if I press the "auto" button with the temp set at 78/79 the "AC" light illuminates. It's easy enough to turn off but I can't figure out why on earth the AC would try and come on when it's cold out and I have the temp set high. Am I doing something wrong? Any ideas?

A/C on = SOP

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wwest demist denso

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I'm a new ES300 owner and have a question about the climate control. It's in the mid-30s outside and if I press the "auto" button with the temp set at 78/79 the "AC" light illuminates. It's easy enough to turn off but I can't figure out why on earth the AC would try and come on when it's cold out and I have the temp set high. Am I doing something wrong? Any ideas?

Climate control systems use many methods to keep the car temperature comfortable. The reason the compressor goes on at lower temperatures is to control the humidy of the air that blows out of the ducts.

As an example: If the outside air temperature is 40 degrees with high humidy, and you have the climate control set to 70 degrees, the air blowing into the car will regulate the car to 70 degrees, but the humidty will also be much higher without the compressor running. When you have the climate control set to auto, it constantly regulates the interior air temperature, humidity, air flow speed and direction to give you optimum comfort.

Another example: You'll notice that in cold, high humidy conditions, if you use the climate control without the compressor turned on you'll get fog(moisture) on the inside of the windows, even though the temperature is correct. At this point, turn on the compressor, and the fog will disappear.

If the outside temperature is cold, and the humidity is low, then you can use this system without the compressor.

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I'm a new ES300 owner and have a question about the climate control. It's in the mid-30s outside and if I press the "auto" button with the temp set at 78/79 the "AC" light illuminates. It's easy enough to turn off but I can't figure out why on earth the AC would try and come on when it's cold out and I have the temp set high. Am I doing something wrong? Any ideas?

Climate control systems use many methods to keep the car temperature comfortable. The reason the compressor goes on at lower temperatures is to control the humidy of the air that blows out of the ducts.

As an example: If the outside air temperature is 40 degrees with high humidy, and you have the climate control set to 70 degrees, the air blowing into the car will regulate the car to 70 degrees, but the humidty will also be much higher without the compressor running. When you have the climate control set to auto, it constantly regulates the interior air temperature, humidity, air flow speed and direction to give you optimum comfort.

Another example: You'll notice that in cold, high humidy conditions, if you use the climate control without the compressor turned on you'll get fog(moisture) on the inside of the windows, even though the temperature is correct. At this point, turn on the compressor, and the fog will disappear.

If the outside temperature is cold, and the humidity is low, then you can use this system without the compressor.

Right on amf1932. Excellant reply and is so true. Best explanation for climate control.

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I'm a new ES300 owner and have a question about the climate control. It's in the mid-30s outside and if I press the "auto" button with the temp set at 78/79 the "AC" light illuminates. It's easy enough to turn off but I can't figure out why on earth the AC would try and come on when it's cold out and I have the temp set high. Am I doing something wrong? Any ideas?

Climate control systems use many methods to keep the car temperature comfortable. The reason the compressor goes on at lower temperatures is to control the humidy of the air that blows out of the ducts.

As an example: If the outside air temperature is 40 degrees with high humidy, and you have the climate control set to 70 degrees, the air blowing into the car will regulate the car to 70 degrees, but the humidty will also be much higher without the compressor running. When you have the climate control set to auto, it constantly regulates the interior air temperature, humidity, air flow speed and direction to give you optimum comfort.

Another example: You'll notice that in cold, high humidy conditions, if you use the climate control without the compressor turned on you'll get fog(moisture) on the inside of the windows, even though the temperature is correct. At this point, turn on the compressor, and the fog will disappear.

If the outside temperature is cold, and the humidity is low, then you can use this system without the compressor.

Right on amf1932. Excellant reply and is so true.

Best explanation for climate control.

NOT..! Absolutely NOT..!!!

Use of the A/C for dehumdification is a total and complete WILD CARD!!!

The A/C cooling evaporator can NEVER cool the incoming FRESH airflow below about 35F and this with the blower motor running at the most EXTREME low speed. In order to dehumidify the incoming airflow the airflow MUST be cooled to its dewpoint or below. The lower the OAT the less is the possibility that the A/C will be an aid in dehumidifying the incoming airflow.

Additionally, what do you think happens to all that condensed moisture remaining on the 10,000 square inches of cooling evaporator vanes once the A/C is shut down, say because the OAT declined below 34F, for instance.

30 years ago when cars had adequate flow through ventilation use of the A/C as a possible AID in defogging the windshield or keeping the cabin atmosphere Rh at a low level was a quite reasonable thing to do. But nowadays with the exhauster ports reduced to minmum anbd the cars so welled sealed to improve FE it is more of a hazard than an asset.

http://us.lexusownersclub.com/forums/index...showtopic=42987

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Use of the A/C for dehumdification is a total and complete WILD CARD!!!

The A/C cooling evaporator can NEVER cool the incoming FRESH airflow below about 35F and this with the blower motor running at the most EXTREME low speed. In order to dehumidify the incoming airflow the airflow MUST be cooled to its dewpoint or below. The lower the OAT the less is the possibility that the A/C will be an aid in dehumidifying the incoming airflow.

Additionally, what do you think happens to all that condensed moisture remaining on the 10,000 square inches of cooling evaporator vanes once the A/C is shut down, say because the OAT declined below 34F, for instance.

30 years ago when cars had adequate flow through ventilation use of the A/C as a possible AID in defogging the windshield or keeping the cabin atmosphere Rh at a low level was a quite reasonable thing to do. But nowadays with the exhauster ports reduced to minmum anbd the cars so welled sealed to improve FE it is more of a hazard than an asset.

http://us.lexusownersclub.com/forums/index...showtopic=42987

You my friend are the most irritating poster on this site with your hypothetical reasons on many subjects......and in all cases I find you a blowhard that try's to intimidate others by using abbreviations, and unfounded knowledge.

A perfect example is the link that you provided for another thread....where other members didn't even understand what the hell you were talking about! :chairshot: Cool it pal!

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Use of the A/C for dehumdification is a total and complete WILD CARD!!!

The A/C cooling evaporator can NEVER cool the incoming FRESH airflow below about 35F and this with the blower motor running at the most EXTREME low speed. In order to dehumidify the incoming airflow the airflow MUST be cooled to its dewpoint or below. The lower the OAT the less is the possibility that the A/C will be an aid in dehumidifying the incoming airflow.

Additionally, what do you think happens to all that condensed moisture remaining on the 10,000 square inches of cooling evaporator vanes once the A/C is shut down, say because the OAT declined below 34F, for instance.

30 years ago when cars had adequate flow through ventilation use of the A/C as a possible AID in defogging the windshield or keeping the cabin atmosphere Rh at a low level was a quite reasonable thing to do. But nowadays with the exhauster ports reduced to minmum anbd the cars so welled sealed to improve FE it is more of a hazard than an asset.

http://us.lexusownersclub.com/forums/index...showtopic=42987

You my friend are the most irritating poster on this site with your hypothetical reasons on many subjects......and in all cases I find you a blowhard that try's to intimidate others by using abbreviations, and unfounded knowledge.

A perfect example is the link that you provided for another thread....where other members didn't even understand what the hell you were talking about! :chairshot: Cool it pal!

Wow...Double WOW...!!

Back many years ago now when I was teaching electronics I tried, really tried, teaching too, at a level, for which the slowest students would follow, would understand. But I soon discovered that when I did that my brighter, brightest students, soon got bored and I "lost" them. So I struck a compromise, I teach, and write dissertations, to the "middle".

Extremely sorry if that leaves you and a few others "out".

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amf1932, wwest,

You two are a real hoot! I always enjoy reading all the posts from both of you. This is the probably the most humorous exchange on this forum I have seen.

Keep it up! Merry Christmas to you both.

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amf1932, wwest,

You two are a real hoot! I always enjoy reading all the posts from both of you. This is the probably the most humorous exchange on this forum I have seen.

Keep it up! Merry Christmas to you both.

Thanx 1990LS, and a Merry Christmas to you too. :cheers:

christmas%20wreath.jpg

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Some of the back light on my climate control panel does not light up. Can anyone give me an idea how much these light bulbs cost at the Lexus/Toyota dealers and can I get them any place else except the dealers. Thanks.

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amf1932, wwest,

You two are a real hoot! I always enjoy reading all the posts from both of you. This is the probably the most humorous exchange on this forum I have seen.

Keep it up! Merry Christmas to you both.

I agree merry christmas to both, I too enjoy them. Is it because one is from the east coast, and one from the west coast???just kidding.

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amf1932, wwest,

You two are a real hoot! I always enjoy reading all the posts from both of you. This is the probably the most humorous exchange on this forum I have seen.

Keep it up! Merry Christmas to you both.

I agree merry christmas to both, I too enjoy them. Is it because one is from the east coast, and one from the west coast???just kidding.

Thanks for the (entertaining) responses. The humidity is the only reason I can think that it would come on.

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