Defogger problems of the 2007 Toyota Prius

I own a 2007 Prius and noticed this problem for several months already. March 7, 2010 was a raining day in san diego. At about noon, I drove my wife to the market with the Prius. I needed to turn on the warm air to defrost the windshield for better visibility. What I got was the cold air from the a/c. I checked the a/c indicator and it wasn't on. I touched the indicator to turn it on then off but nothing changed. The air was still cold. After shopping at the market, we started the Prius again to drive home. The air then changed to warm. What we learned was only a total turn off could change the 'stuck' condition in the Prius. This was not a dangerous incident but it could relate to the electronics malfunction in another serious accident.

We own a Toyota Prius. When we turn on the heater and turn it to the feet, warm air starts blowing from the vent on the driver side to the face. We took it to the dealer "capitol Toyota", capital auto mall, san jose, CA. The dealer said that they would charge big time to fix it since we were just over 36,000 miles in 30 months. We didn't get it fixed. We believe that this issue is somehow related to its electrical/electronic systems issue. We also noticed about 2 weeks ago when we were parked in the line for gas, that the engine suddenly was roaring as if we were revving it to very high speeds without even the heater or a/c being on. We also think it has related front defrosting issues.