Fall is here, I usually never turn my AC on during fall and spring. With our older cars, we just let the fresh air in thru vent.
How can we do this on our TCH?

 

You can turn off the A/C button and recirc button, set temp to LO and set whatever fan speed you want (ie you've gone completely manual) to get whatever the outside air is. I used to do this because I rarely like to use A/C in fall and spring either.

Lately however, I've decided that leaving the system in Auto with A/C lit (meaning "available" but not necessarily "on") is easier and probably isn't using the A/C much if at all if its cool outside. I've also had my recirc button programmed so that it's not automatic (ie its always on fresh air setting). Just set the temp setting as high as is perfectly comfortable to minimize/prevent the A/C from actually being used.

 

I wish Toyota would install a compressor running led on the dash. One that would light up blue for cold when the compressor is running.

I'm sure I could save some gas with a simple feature like that.

I had a early 80's VW diesel rabbit. I installed a small 12 volt bulb on my dash and connected it to the AC compressor clutch wire. I picked up 3 to 4 city mpg by learning how best to set the air conditioning.

 

I usually turn off recirc and pop the sun roof up and it draws fresh air in, works well for me.

 

Modern day cars, as a general rule, keep the A/C evaporator as close to ~34F anytime the A/C is "enabled", the compressor runs anytime the high side pressure switch demands such.