I need help in keeping the fog off windsheild without running the air conditioning? is this possible? So far when I fog up the only way to remedy is the set the air on and it clears fast.... thanks for the help Mr Bosox!

 

Apart from having a warm car to start with... heat is your friend but I assume the fog is from a cold start in the morning?

The fastest is the A/C. Also, make sure you are NOT recycling the air. You want to remove the moisture in the air.

There are some anti-fogging solutions out there, you apply them on your windshield but I think they leave more of a mess then help. A clean window (use stoner's) is also your friend.

 

To clear fog from front windshield use the defrost button on the steering wheel. That is your direct access button. Press is once and the defrost light iluminates on the dash. Press it once again and it will return your system back to its prior operating condition.

If you are concerned about the A/C light on the Air Conditioning control screen, that is nothing more than a lockout light. It does not indicate if the compressor is operating. It does indicate that the system can use the a/c compressor when it needs to if iluminated and if not iluminated that the compressor is not accessible. If you press the a/c button on the touch screen to turn off the a/c light the system will not call on the compressor even if conditions warrent it.

Air conditioning systems in cars do operate in the winter when the system is placed in defrost to help dehumidify the vehicle interior. Air conditioning is a very powerful dehumidifier on top of providing cool air in the summer. In the winter they provide the functionality of dehumidifying the air and shortening the time it takes to eliminate fog on a windshield and helping to prevent that fog from coming back. Yes, the a/c system will cool the air when the compressor is on, however most vehicle heaters, including the Prius's heater will easily overpower the a/c system and provide heat above and beyond the system's ability to provide cool.

Keep in mind that Toyota uses a/c and Air Conditioning to mean both the compressor that provides refrigerant to cool air, and the entire cabin climate control system itself. The best adivce, aside from using defrost when necessary, is "set it and forget it". Leave the a/c switch on the Air Conditioning touch screen on and just set the temperature. The vehicle is smart it will do what is necessary to maintain the cabin temp you select.