Chevrolet Repair: a/c - heater, vacuum leak, condensor

Question
I have air coming out of all vents at the same time and hear a slight hissing inside the car.  What do I do? This just start when I changed the heater control box cause the lights where out in it. Please explain in detail and / or with pics.....I am new at this.  Where is the a/c evaporator and condensor also.  Oh I have a 98 cavalier with a 2.2.

Answer
Hi Marcy, What I think is happening is that the part you have is bad or the vacuum connection to the head (control box) are not correct and making a vacuum leak which will cause the problem your having.
Check the connections and or replace the control head.

Have a Great Day                    Mark