Couple of thoughts, could be wrong of course, the A/C on button if lit may mean in "auto mode" if off, then off. In "auto" compressor will vary according to amount of cooling required or may cycle off if not needed. I think the A/C on button is more appropriately called an "enable" button.

If the fan is off and fresh air selected, there may be some air flow and if compressor in "auto" it may run, but if there is zero air flow, not likely compressor would run. Evaporator coil would turn to a block of ice. There would be safeties to prevent that, so no air flow then no compressor.

Does manually turning off the compressor extend either the life of the engine, the batteries or the compressor? Sure, but personally I'm not going to worry about exceeding "the mean time between failure" runtime of these components. If I was trying to squeeze every mile per gallon out of a 450, I might turn it off. First I'd switch the 450 to ECO mode and let the computer do it. Then if that didn't do it, I'd turn off the compressor.

However, right now it's kinda hot outside and I want the compressor, fan and seat ventilation running at full bore and mileage be.....bad.

 

I agree David.

What's the point of owning a Luxury Vehicle if you're are going to drive around uncomfortable. Full bore on all aspects of cooling.

 

Here's the thing though, every other car on the planet (or at least the ones I'm aware of) let me control the AC directly from he dash. And I've had cars 200k miles and I've manually controlled the AC in every one and have never replaced anything to do with the climate control system. It's not a big deal but annoying.
More annoying was the car constantly going into recirculate mode when 99.99% of the times want fresh air.
Luckily the people here told me how to reprogram it.

 

i didnt know that the ac stays on when you turn the fan off
what if you press the ac button and the light turns off?
i have a 2010 rx
thanks

 

David, I live in the Houston area and whole-heartedly concur that I want AC everything on all the time. I'm not sure about mileage being "bad" tho. . .on my current tank (about half full) I'm averaging around 30mpg. I think I'm starting to figure out how to drive this thing!

 

That will turn the air off. On cars with navigation you have to work through the menus to turn it off..

 

i dont have navigation
thanks for the recomendation marqevans