2010 Lancer GTS A/C??
 

When I put the A/C to the lowest temperature and turn it up half way, warm air comes out of the vents. The outside temp is about 90 degress ferenheit. What could this be due to? Also, when I turn the A/C on, theres a hissing noise that seems to come from the engine that increases in pitch when i press on the accelerator.