The outside temperature has been cold since the purchase of my 07 SC almost 2 weeks ago (below freezing F ). The A/C green light has not been lit. My 05 SC, the light was on all the time. Dealer says the system will turn the A/C off in certain circumstances in very cold conditions. What do you think?

 

There are a couple of possiblities here. Yes, there is an ambient temperature sensor circuit. The DTC can easily check this. If it's throwing a B1412/12 code there is an issue. The sensor has a range of -9°F to 150°F. There are a few other failure points, the wiring harness, air conditioning amplifer and the senor or cooler thermistor itself.

There is also a customizable feature that can be programmed into your 07. It has to do with the "Compressor Mode" the default is "Auto" which turns the A/C on automatically. A second setting is manual. There is a slight chance the previous owner changed it. These changes are "SUPPOSE" to entered into the National Service Database so when new owner take possession and has issues like this any dealer can check it. The trick is was it entered if it was done????

Of course there is another possiblity I just thought of ...the little green light could be burned out. There is a diagnosic for the display that will blink all the lights. To access the diagnostic turn the ignition switch ON with the AUTO and R/F switches held down. (See the graphic below) To cancel the diagnostic just press the OFF switch.

So the first thing I'd do is call your dealer, have them look into the service database and see if any customizable programming was done on your car. If not, you've got two choices, wait for warmer weather and see if that resolves it, or go in and have them scan it for trouble code(s).

I have a whole list of trouble codes that can be displayed on the panel (like the #21) below indicating a problem. BTW 21 refers to the solar sensor. I got the same code when I checked my car ... it was dark in the garage.

Good Luck.

 

Thank You very much VVTiBob. I sent this to my Dealer to investigate.

 

The reason the A/C comes on when not in summer heat is for the purpose of dehumidifying the air. I suspect that the A/C is not coming on (hence, the light is not on) because the relative humidity is very low. Very cold temperatures are usually accompanied by low RH. Perhaps this will change once the humidity increases.

 

On my 06 the AC light goes off at about 30 degrees and below.

 

drove my SC today when it was 13 degrees out and 20mph winds made it close to zero in sunny Dallas and the green light on A/C was on. Maybe different for 2005?

I run my a/c year round anyway on the car for RH control anyway. Always have on all cars.

Have you noticed your SC fogging up more now too with the light not on? Perhaps it's a setting, but could just be the little indicator light...or maybe your compressor? Dealer will take car of it...you should be fine under warranty.

 

scdroptop, my light has been off and I haven't noticed any fogging issue unless the humidity is higher. Recently, that hasn't been a problem.

 

My Temp change buttons will not decrease the temp setting. I ran the above diagnostic test and got codes 24 and 21. Does anyone have any helpful tips and what the 24 code means?

 

Did you run the diagnostic inside a garage? 24 is the solar sensor. You'd get this error if you ran the test inside a garage, or some other place the sun doesn't shine. (Please...no comments are necessary).

24 also points to wire harness between the sensor and the A/C amplifier.

 

An update. Problem solved. The navigation system has been off the whole time the Temp down button would not work. I finally noticed this and decided to try turning it back on to test the climate control system. It started working perfectly again. Hope this will help others! Although it could be a quirk of the CCU on this car. Thanks for your for the input, also.

 

I have a problem with my AC too. If the temp is around 75 or less, the AC would run really good without problems. But if the outside temp is around 80 or more, the AC won't come on. Run diagnostic test and got code 21 and 24. I had the test run outside under sunlight. My navigation is on and got no problem. The ambient sensor still reading outside temp correctly. Anyone got the same problem fixed?

 

Can you tell us more? Does it ever start? Does it run and then stop?


Is the pressure in your system set properly? If it is over pressure when the car is in 80 degree weather, the high pressure switch cuts off your A/C.


Have you checked your relays? Could one be overheating and cutting out?


Does anyone know if the ambient temp sensor and the outside temp sensor are the same? I had a Z4 and there was on sensor for each function. (two total) Is the SC430 the same?

 

Went to Lexus dealer last Friday to buy the sensors but they didn't have them in stock. So I decided to do more researches before special order them. Got out to the car and dpunle checked the codes, it gave me no code (00). Started the car and AC ran fine ever since. The temp here in Kansas has gotten to 95 degree and I got cold AC. Weird huh?