Air Conditioner

[Canopy]

Just purchased a nice hunter green 2000 LS 400 from private party for $17,500 with 74,480 miles to go with my wife's 1996 white pearl LS 400 (which I coveted).

Think I got a pretty good deal, but on the drive home noticed that when the air conditioner buttons are changed from "Cold" on both sides to 66, 67, etc. the air becomes warm on both automatic and non-automatic.

On "Cold" it is ice cold on both automatic and non-automatic so the compressor seems to be working fine. Blowers work fine as well.

Any suggestions?

[SKperformance]

Maybe the temp sensor in the dash has been blocked or disconnected.

Check the tutorials or general maintance section for pages on how to check it for codes.

[wwest]

What is your definition of warm??

The Lexus climate control, absent being in max cooling, uses a reheat/remix method wherein ALL of the system airflow is first chilled via passing through a COLD A/C evaporator and then a selected portion (ALL, in the case of max heating) is diverted through the heater to be reheated. Both portions are then remixed resulting in air outflow that is not so cold as to be discomforting but still cool enough to eventually cool the cabin down to the temperature setpoint. As the cabin reaches your temperature setpoint the system airflow, in cooling mode, will sometimes be only about 2F below the setpoint.

This effect will be even more pronounced if the solar radiation sensor(s )(at the bottom of the windshield near the defroster ducts) are not exposed to bright sunlight.

Personally when I am traveling in the South, or any area of HOT climate, I turn these automatic climate control systems to MAX COOLING and then use the blower speed to adjust/keep the system to/at my comfort level.

The efficiency of the A/C is increased dramatically via this method resulting in fewer compressor cycles, lower heat loading on the engine cooling radiator and increased fuel economy.

[Canopy]

Thanks, WWest, for such a scholarly reply. Complicated, isn't it?

"Warm" is really warm, like it's coming from the heater (although since we're having 95 degree weather currently, it's hard to be sure).

On "max cool" it's really cold, and I've been adjusting the blower as you suggested. Since I take my daughter to school in the morning and she prefers it to be warmer on the passenger side, she adjusts the temperature up a notch to 65 and the result is warm air on her side and cold air on my side. Dualing comfort controls, I guess.

This is something I need to fix, but don't know where to start. Maybe it's all electrical or all computer. But I'm hoping it's something mechanical.

[wwest]

Is the outside temperature indication correct? An open OAT sensor will indicate and extremely low OAT and that will result in your problem.

[vovka]

I just took my 1990 LS400 in (07SEP05) and mentioned to the mechanic that when the A/C is set at 65° it works pretty good, but when I go to 66/67/68 heat starts blowing. He immediately knew what it was and it didn't cost a dime. A temp sensor was unplugged under the hood near the passenger headlight right below the front bumper.

If I were you - and I don't know if the A/C setup is the same for the two cars - this seems like a good and cheap place to start.

By the way my A/C works great for the first time in a year.

[Canopy]

I just took my 1990 LS400 in  (07SEP05) and mentioned to the mechanic that when the A/C is set at 65° it works pretty good, but when I go to 66/67/68 heat starts blowing.  He immediately knew what it was and it didn't cost a dime.  A temp sensor was unplugged under the hood near the passenger headlight right below the front bumper.

If I were you - and I don't know if the A/C setup is the same for the two cars - this seems like a good and cheap place to start.

By the way my A/C works great for the first time in a year.

←

That sounds exactly like my problem. Thanks for responding. Do you know what the sensor looks like? I looked underneath the passenger side headlight around the bumper and I see what appears to be an electrical connection plugged into something about a square inch in area. If that's it, it looks plugged in but it might be a bad sensor, or perhaps there's a bad connection somewhere else.

WWest, no, the outside air temperature seems to be spot on, but thanks for the suggestion and for continuing to think about it.

[wwest]

I just took my 1990 LS400 in  (07SEP05) and mentioned to the mechanic that when the A/C is set at 65° it works pretty good, but when I go to 66/67/68 heat starts blowing.  He immediately knew what it was and it didn't cost a dime.  A temp sensor was unplugged under the hood near the passenger headlight right below the front bumper.

If I were you - and I don't know if the A/C setup is the same for the two cars - this seems like a good and cheap place to start.

By the way my A/C works great for the first time in a year.

←

That sounds exactly like my problem. Thanks for responding. Do you know what the sensor looks like? I looked underneath the passenger side headlight around the bumper and I see what appears to be an electrical connection plugged into something about a square inch in area. If that's it, it looks plugged in but it might be a bad sensor, or perhaps there's a bad connection somewhere else.

WWest, no, the outside air temperature seems to be spot on, but thanks for the suggestion and for continuing to think about it.

←

The temperature sensor mounted on, behind the front bumper is the OAT sensor and is used as an A/C input and for the OAT display. Sorry.