I was sitting in the car the other day (waiting to pick up someone at the airport pickup) and it was very hot and humid.
I turned the car off and back on again (without foot on brake), so the READY light was off.
The AC light was on, but the it was just blowing air. When I turned the enginge back on (READY illuminated) the air got colder.
I had a full battery at the time.
I understand the AC runs off battery power and not the engine, so I was surprised it wasn't cooling the air. I know the AC saps a lot of power and could quickly drain the battery, but I would have thought the AC would run as long as the battery had sufficient charge. For example, AC runs as long as charge is >50%, etc.
I guess this is a battery saving feature, but was surprised, nonetheless.

 

This is just a guess, but I think that the AC does not work unless the car is in ready mode because it can potentially drain your battery completely. The car would need to be in ready mode so that the engine can start when needed to keep that from happening.

 

Some nights I would take my wife to the store. I would go out and sit in the car a few minutes while waiting for my wife. It was a warm night so I pressed the power button till the dash lit up. I turned on the AC and it blew out cold air but not near as cold as when driving. I ran it for about two minutes and noticed the battery display dropped about 10%. I had the fan on low at the time. The traction battery was reading 80% before I turned on the AC.

 

If AC compressor was running it could discharge traction battery in less than 10 min. even if it was fully charged at the beginning, therefore compressor won't run unless the car is in "ready" mode so the engine can kick in to recharge. Fan will run in ACC mode and if evaporator is cold enough, it will provide some cooling, until it warms up, as a matter of fact unless it is extremely hot, compressor will cycle on and off while driving, since the temperature of the coil could go bellow freezing and it will take some time for the circulating air to warm it up. I don't remember exactly but I think car evaporator can be cooled down to around 50F bellow ambient. To be honest, IMO TCH doesn't really need any other mode than "ready" and I rarely use anything else. Once warm, the engine will not run when parked, except to recharge battery and you don't want battery discharged, ever. In cold winter the engine will kick in more often to keep catalytic converter at operating temperature, but I think they used faulty logic here, most of the time there is more pollution created by keeping catalytic converter hot at all times. Forcing the engine to kick in at every car start, even if the engine is hot, is also very wasteful, especially during short trips but that's another topic.

 

Maybe they could have written a three line program and added it to the computer
1. If car is not in READY state and person presses AUTO, AC light does not illuminate, go to line 3
2. If car is in READY state and person presses AUTO, AC light illuminates, go to line 3
3. End

 

I found using the AC when sitting still with the ice off, I had to turn the temp down to 60 degrees to get any cold air.