1996 mercury cougar xr7 196k
 

so i just bought the car and i must say i love it . i sold my 1992 buick lesabre with 109k for 600$ and bought this for 500$ a steal rite? well i noticed that the AC turns on and blows cold for a little then gets a little warm. when i switch frm low to medium then medium to high the air pressure does change it just doesnt stay cold how can i fix this is it an easy solution. my mother and father suggested it just probably needs to be recharged . HELP