Climate Control

[redhawks2]

Hello...I have a '90 ls400 and the AC only blows cold air when it is set at 65. It will not go below 65 and if I set it at 66, it starts blowing warm air. This doesn't seem right to me. I bought the car used and it has always been this way so I don't know how it's supposed to work. I replaced the temp display module recently because the display had burned out. Could there be something wrong with the unit in back of the temp display? Thanks for any info.

[Rich Sweitzer]

Sounds like an air mix damper position sensor problem. The ECU will give nothing but cold air when set to 65-degrees, only hot air when set to 85-degrees. In between it mixes the hot and cold to acheive the programmed temperature. You can switch back and forth between the two extremes so it sounds like the actual damper motor is working.

On my '91 you can put the ac control computer into diagnostic mode by holding the AUTO and REC switchs both in while turning on the ignition. The thing will go an indicator test by lighting all of the indicators and sounding the buzzer four times in a row. Then it goes into diagnostic mode automatically and displays one or more two-digit diagnostic codes in the temp window (if there is a problem). Code 31, 33 or 34 will point to that sensor.

The sensor is not easy to get to (deep under the dash) so if you want to tackle deeper diagnostics or repair on your own you should probably get a copy of the service manual from Lexus. Their manuals are very good.

[redhawks2]

Hello and thanks for the info. One thing, on my head unit I see the auto button but I don't see anything that says REC. Perhaps there is a different type of AC unit in the '91?

Thanks.

[VBdenny]

he REC button mean recirculate. This is essence is the same as hitting the MAX button is American made cars. Many people think that max does some supercharging or the A/C system when all it really does is put the fan blowere on super high and recirculates the air inside the car therefore starting with already cooled air rather than hot 95 degree outside air. If you need to run this to get cool air, your Freon charge is possibly a little low. Also most A/C units use a circuit breaker which cuts off the compressor when the charge is low to prevent damage.

[redhawks2]

Thanks again for the info! :)

[redhawks2]

Hello...I tried out the "pushing in the auto and rec buttons while turning on the ignition" and by golly I got a diagnostic code of 11 on the display. Anyone know what that means?

Thanks!! :o

[zigenfiver]

Hello...I have a '90 ls400 and the AC only blows cold air when it is set at 65. It will not go below 65 and if I set it at 66, it starts blowing warm air. This doesn't seem right to me. I bought the car used and it has always been this way so I don't know how it's supposed to work. I replaced the temp display module recently because the display had burned out. Could there be something wrong with the unit in back of the temp display? Thanks for any info.

Check to see if the temperature sensor is plugged in. It is sometimes left unplugged during Alarm or Stereo installs. It is located under the steering column, and plugs in behind the removable panel.

[redhawks2]

Thanks for the tip... will check out the sensor this weekend!

[VBdenny]

I think the 11 is because it is too dark when you checked it. Apprently, there is a sunlight sensor or something on the right side of the dash. Somewhere I have a list of codes, if I find them I will post them. I'm sure VMF knows because I think he was the one who originally posted them.

[redhawks2]

Well I checked under the steering column/panel and couldn't see any loose connections (lots of wiring under there). I tried the code check again in bright sunlight and still got an 11 on the display.