I usually don't use the "Auto" function on the temperature controls, but when I accidentally pushed it, the "A/C" button lit up. And this is with the temperature set well into the heating temperatures (this is Canada afterall).

If I select "Auto", not only does the "A/C" button light up, but the air flow changes from whatever it was on to the floor vents only. As far as I can tell, the temperature of the air doesn't change.

What's going on here?

 

This is pretty standard with the Lexus auto climate controls. The auto setting runs the A/C compressor to remove moisture from the air inside the vehicle. When the compressor runs, the A/C light will be lit. I have never seen my A/C light be off when I run the auto climate control, so I guess it runs the A/C compressor even if it is heating the cabin.

 

I haven't owned too many different manufacturer cars, but all my auto climate controled cars do that. Just like it was mentioned above, the AC turns on and acts as a dehimidifier. The temp should be hot air if you select hot though.

 

In my RX330 the AC light comes on when I push auto but I can turn it off if I want. Is this a problem?

 

Sounds normal to me.

 

The "Auto" function, when enabled (green light on), keeps the AC compressor clutch engaged, chilling the evaporator coil. Temperature is regulated by circulating varying amounts of heated air over the evaporator which also serves to remove moisture from the air when outside air temperature is below the setpoint.

In winter, particularly in very cold climates, you may not wish to run the AC in this manner, especially since until the engine is warm, you are only recirculating the cabin air - and are actually cooling a portion of it. (Brrrrr!) Once the engine is warmed up, the heater functions normally, but without the evaporator being chilled, you may need to operate the defroster/defogger to keep the windows clear.

In summer, blending chilled air with varying amounts of heat keeps the cabin at setpoint, rather than by cycling the compressor on and off as your home AC or most conventional automotive units do. This is not as wasteful as we might think because the compressor is always turning, rather than engaging suddenly at speed against pressure.

I'm no expert, especially living in a warm climate, I probably don't get to experience the extreme cold performance of the system, but I seldom if ever turn the "Auto" off. Even on cold (30-40 degree), wet mornings, the cabin is warm within a few minutes and I never need the defroster/defoggers. Of course, the seat heaters help a lot!

 

When I put the temp to "Lo" I noticed that the recycle air flow button light comes on once you turn it off and turn it back on. Is this normal? Do all of you have the same issue?

 

If you don't like the A/C always coming on in AUTO mode ... I believe it's a C-Best setting you can have changed at the dealer.

Seems like the heater gets cranking REALLY quick on the RX .... much appreciated ... and like mentioned, the seat heaters really crank too!

 

Just the way Toyota/Lexus designed their A/C systems. I find this annoying as well especially during winter months. I don't need A/C to clear the windshield fog as Colorado winter is bone dry.

Also like you said, the Auto setting sends heat to the floor vents only. I have to push the vent button twice to get warm air from the dash vents. Unfortunately there's no C-Best setting for any of these.