Why is it that when I start my car and on the AC I hear smell

Pls whats wrong with my Honda Accord EOD 2004.. Whenever I start car and put on the AC I hear smell like something is burning and the AC is not cooling fine anymore pls what meant cos that.... And also my meter drops below 1... Before it's on 1or more now drops below one.. Need a good expect on this.. Also u can Email me on segxyworld@yahoo.com.