Ok heres the deal. I have checked all my vaccum hoses and even hooked the hoses up running from my firewall. Air blows out of all the vents, (defrost, dash vents, heater vents) but there is still a hissing noise coming from my ac/heater controls. The weird thing is that the hissing is at its worst when I move the temp controls all the way to warm. Whats up?

 

Normal. When in various positions the non used flapper door vacuum solenoids leak air at the head unit allowing them to return to the neutral position

 

Cool, thanks for the tip!