When I have my AC set on "Max" and I then turn it to the "Off" position a suttle "tssssssssssss" (rushing air) sound occurs for about 3 seconds then goes away. Also, when I take my car to the track and really get on the gas the windshield will begin to fog up until I let off at the end of the track.

 

the rushing sound is normal, just vacum I think.

 

The hissing sound is normal. I have the same sound when I turn the dial. As far as the fogging windshield, I have no clue. But usually it is going to be caused by going from one temp. extreme to another. Think about when you are in the grocery store and you open the freezer door to get some ice cream, bam, instant fog on the door. Just a thought.

 

alright, thanks for the info on the AC sound. but does anyone else have excessive fogging of the windshield when running at the track? I guess hot air is coming up through the vent on top of the dash (near the windshield). During a quarter mile run, by the time I'm about 1/3 to 1/2 of the way down the track I can HARDLY see through my windshield for a few seconds, which makes me extremely nervous! Is it bad to cover up the vent on the top of the dash?

 

sounds like your heater core may be blown

 

the sound is normal



i think the fog is normal too.................whenever i start my car at night, it always fogs up the window above the vent for the first 5 mins, then goes away.

its just warm air coming up the vent and hitting the colder glass.