I have a 2011 Prius 2. 11000 miles. All stock. While sitting in a parking lot eating today I had the AC set to COLD and a low fan speed, blowing on my face. about 5 minutes later it randomly switched to defrost, and to blow on my feet, and it increased the fan speed. I figured maybe it was because the car was parked and conserving battery or something...who knows. Anyway I reset everything to when I was driving, and about 5 minutes later it switched again. The AC was not set on "auto" either. Is this normal or does it sound like a possible failure?
No, it's very much alive. It seems like it behaved like it switched to Auto. I've had the car decide start running the fan faster when adjusting the temperature, but one press of a button and it started behaving again. I'd call it an occasional glitch.
Was it in Auto? If so, press Mode till you get the setting you want. It should not change if Auto is not selected. In Auto, it will switch to the Mode it thinks will provide the best effeciency, which may not necessarily be the best comfort setting.
Ironically, I've noticed mine doing this periodically when it's turned OFF. It hasn't switched to Foot/Defog but it has moved between foot, foot/face, and just face before. I only noticed because I'd feel an ever so slight breeze on my face from the fresh air coming into the car. As for it doing so otherwise? I don't believe it has, at least not without it being set to AUTO.
Maybe it has something to do with keeping the air in the rear of the car cool enough for the fan drawing air to cool the battery???
I have an 09 so the set-up is a bit different than your car, but could you have hit one of the steering wheel controls by mistake?
It sure doesn't sound normal. I always run my system in Auto and have always had air coming out of the face vents when it's been hot. This is just speculation, but perhaps after running on the "cold" setting long enough the controller anticipated condensation and switched to defrost mode. Or maybe you have a flaky controller.
